Deep X-ray observations of SN 2014J reveal no X-ray emission down to a luminosity limit of Lx < 7 × 1036 ergs−1, constraining the mass-loss rate of the progenitor system to be < 10−9 M☉/yr. Alternatively, the SN shock could be expanding into a uniform medium with density < 3 cm−3. These results rule out single-degenerate systems with steady mass transfer until explosion and constrain unstable hydrogen burning systems to have recurrence times < 300 years. Allowed progenitors include double white dwarf systems or systems where mass transfer ceased before explosion.
This document summarizes observations of IGR J12580+0134, a newly discovered hard X-ray source associated with the Seyfert 2 galaxy NGC 4845, which underwent an unusual X-ray flare. Follow-up observations with XMM-Newton, Swift, MAXI, and INTEGRAL are presented and analyzed. The spectrum is well described by an absorbed power law plus soft excess. The hard X-ray flux increased over weeks and decreased over a year as expected for a tidal disruption event. Fast variations near peak allowed estimating the black hole mass as ∼3×105 M⊙, indicating disruption of ∼10% of a 14-30 Jupiter mass object. Hard X-ray emission is from a corona forming
This document summarizes an X-ray study of the supernova remnant G352.7-0.1 using data from XMM-Newton and Chandra observations. Prior observations revealed G352.7-0.1 has a shell-like radio morphology but center-filled thermal X-ray morphology, classifying it as a mixed-morphology supernova remnant. The new observations confirm the X-ray emission comes from the interior and is dominated by ejecta. Spectra from XMM-Newton are fit by a single thermal component with enhanced silicon and sulfur. Some Chandra spectra require a second thermal component to fit, with solar abundances providing a better physical model. No evidence of overionization was found. A neutron
Apartes de la Conferencia de la SJG del 14 y 21 de Enero de 2012: Neutrino ma...SOCIEDAD JULIO GARAVITO
This document discusses a novel method for determining neutrino mass spectra using gravitational waves and neutrinos from supernovae. It proposes that two bursts of gravitational waves could be generated during neutrino oscillations in supernovae: one from neutrinos converting from left-handed to right-handed states via interaction with the magnetic field of the expanding plasma, and another when some of these right-handed neutrinos flip back to left-handed flavors later due to a different interaction. Measuring the time delay between the arrival of neutrinos and gravitational waves could directly measure neutrino masses, since massive neutrinos would be delayed relative to massless gravitational waves. This could provide a new way to determine absolute neutrino masses that does not depend on mass-squared differences
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
Discovery of powerful gamma ray flares from the crab nebulaSérgio Sacani
1) The AGILE satellite detected powerful gamma-ray flares from the Crab Nebula in September 2010 and October 2007 that increased the nebula's unpulsed gamma-ray flux by a factor of 3.
2) The flares originated near the nebula's central pulsar and challenge standard models of nebular emission.
3) Synchrotron emission from shock-accelerated electrons along the pulsar's polar jet can explain the gamma-ray flaring, requiring particle acceleration on timescales of about 1 day.
A young protoplanet_candidate_embedded_in_the_circumstellar_disk_of_hd100546Sérgio Sacani
This document summarizes observations of HD100546 using high-contrast imaging techniques. A faint emission source was detected near the star at a projected separation of about 47 AU. The position of the source coincides with a deficit in polarization observed from the circumstellar disk. This suggests a physical link between the source and the disk. Considering various scenarios, the authors favor interpreting the source as a young protoplanet currently forming within the disk. Follow-up observations could distinguish between different possible explanations for the observed features. If confirmed, it would be a unique opportunity to study giant planet formation within an optically thick disk.
The Light from the Invisible World of NeutrinosSon Cao
The document summarizes a presentation given on neutrino research. It begins with a brief history of neutrinos, including their theoretical postulation in 1930 and first experimental detection in 1956. It then discusses the topic of neutrino oscillation, which provides evidence that neutrinos have mass and mix between flavor states. The presentation also outlines how neutrino oscillation experiments work by measuring probabilities of different neutrino flavors at a baseline, and provides the T2K experiment as an example. Finally, it discusses the importance of neutrino oscillation in going beyond the Standard Model of particle physics.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
This document summarizes observations of IGR J12580+0134, a newly discovered hard X-ray source associated with the Seyfert 2 galaxy NGC 4845, which underwent an unusual X-ray flare. Follow-up observations with XMM-Newton, Swift, MAXI, and INTEGRAL are presented and analyzed. The spectrum is well described by an absorbed power law plus soft excess. The hard X-ray flux increased over weeks and decreased over a year as expected for a tidal disruption event. Fast variations near peak allowed estimating the black hole mass as ∼3×105 M⊙, indicating disruption of ∼10% of a 14-30 Jupiter mass object. Hard X-ray emission is from a corona forming
This document summarizes an X-ray study of the supernova remnant G352.7-0.1 using data from XMM-Newton and Chandra observations. Prior observations revealed G352.7-0.1 has a shell-like radio morphology but center-filled thermal X-ray morphology, classifying it as a mixed-morphology supernova remnant. The new observations confirm the X-ray emission comes from the interior and is dominated by ejecta. Spectra from XMM-Newton are fit by a single thermal component with enhanced silicon and sulfur. Some Chandra spectra require a second thermal component to fit, with solar abundances providing a better physical model. No evidence of overionization was found. A neutron
Apartes de la Conferencia de la SJG del 14 y 21 de Enero de 2012: Neutrino ma...SOCIEDAD JULIO GARAVITO
This document discusses a novel method for determining neutrino mass spectra using gravitational waves and neutrinos from supernovae. It proposes that two bursts of gravitational waves could be generated during neutrino oscillations in supernovae: one from neutrinos converting from left-handed to right-handed states via interaction with the magnetic field of the expanding plasma, and another when some of these right-handed neutrinos flip back to left-handed flavors later due to a different interaction. Measuring the time delay between the arrival of neutrinos and gravitational waves could directly measure neutrino masses, since massive neutrinos would be delayed relative to massless gravitational waves. This could provide a new way to determine absolute neutrino masses that does not depend on mass-squared differences
Extended x ray emission in the h i cavity of ngc 4151- galaxy-scale active ga...Sérgio Sacani
The document summarizes the discovery of diffuse soft X-ray emission extending about 2 kpc from the active nucleus of NGC 4151, filling the cavity of H i material. The X-ray emission has a luminosity of about 1039 erg s-1 and can be fit with either a thermal plasma model with a temperature of around 0.25 keV, or a photoionized model. This interaction between the AGN and interstellar medium implies the last episode of high nuclear activity occurred relatively recently, around 104 years ago.
Discovery of powerful gamma ray flares from the crab nebulaSérgio Sacani
1) The AGILE satellite detected powerful gamma-ray flares from the Crab Nebula in September 2010 and October 2007 that increased the nebula's unpulsed gamma-ray flux by a factor of 3.
2) The flares originated near the nebula's central pulsar and challenge standard models of nebular emission.
3) Synchrotron emission from shock-accelerated electrons along the pulsar's polar jet can explain the gamma-ray flaring, requiring particle acceleration on timescales of about 1 day.
A young protoplanet_candidate_embedded_in_the_circumstellar_disk_of_hd100546Sérgio Sacani
This document summarizes observations of HD100546 using high-contrast imaging techniques. A faint emission source was detected near the star at a projected separation of about 47 AU. The position of the source coincides with a deficit in polarization observed from the circumstellar disk. This suggests a physical link between the source and the disk. Considering various scenarios, the authors favor interpreting the source as a young protoplanet currently forming within the disk. Follow-up observations could distinguish between different possible explanations for the observed features. If confirmed, it would be a unique opportunity to study giant planet formation within an optically thick disk.
The Light from the Invisible World of NeutrinosSon Cao
The document summarizes a presentation given on neutrino research. It begins with a brief history of neutrinos, including their theoretical postulation in 1930 and first experimental detection in 1956. It then discusses the topic of neutrino oscillation, which provides evidence that neutrinos have mass and mix between flavor states. The presentation also outlines how neutrino oscillation experiments work by measuring probabilities of different neutrino flavors at a baseline, and provides the T2K experiment as an example. Finally, it discusses the importance of neutrino oscillation in going beyond the Standard Model of particle physics.
A possible carbonrich_interior_in_superearth_55_cancrieSérgio Sacani
1) The document analyzes the possibility that the interior of the super-Earth exoplanet 55 Cancri e could be carbon-rich rather than oxygen-rich.
2) Models that assume an oxygen-rich interior with iron, silicates, and a water envelope cannot fully explain 55 Cancri e's mass and radius measurements. However, a carbon-rich interior containing iron, silicon carbide, and/or carbon could explain the observations without needing a volatile envelope.
3) A carbon-rich interior for 55 Cancri e is plausible given the reported carbon-rich composition of its host star, though more data is needed on the star's elemental abundances and the planet's atmosphere.
Detection of visible light from the darkest worldSérgio Sacani
This document reports the detection of visible light from the exoplanet TrES-2b using Kepler photometry data. The analysis finds a day-night contrast amplitude of 6.5 ± 1.9 parts per million, representing the lowest amplitude orbital phase variation discovered. This signal is detected at a confidence level of 99.98% and persists across different models of the data, appearing robust. If interpreted as scattering, it corresponds to a geometric albedo of 0.0253±0.0072 for TrES-2b, making it the darkest exoplanet detected so far. However, models indicate significant day-side emission, implying an even lower true albedo.
Too much pasta_for_pulsars_to_spin_downSérgio Sacani
This document summarizes a study investigating why no isolated X-ray pulsars have been observed with spin periods longer than 12 seconds. The researchers suggest this is due to a highly resistive layer in the inner crust of neutron stars, which is expected to be in a state called "nuclear pasta". Nuclear pasta has an irregular structure that increases electrical resistivity, limiting the spin-down of pulsars. Modeling the long-term magnetic field evolution incorporating a resistive nuclear pasta layer successfully reproduced the observed 12 second period limit. The results provide the first potential observational evidence for the existence of nuclear pasta in neutron star crusts.
The document summarizes two Chandra X-ray observations of the Type IIn supernova SN 2010jl taken around two months and one year after explosion. The first observation revealed a high temperature (10 keV) and very high absorption column density (1024 cm-2) from circumstellar matter. The second observation, one year later, showed the absorption column had decreased by a factor of three as expected from shock propagation. Both observations detected an unabsorbed luminosity of 7×1041 erg s-1. The Fe line detected in the first observation was not present in the second.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
This document analyzes the gamma-ray signal from the central Milky Way that is consistent with emission from annihilating dark matter particles. The authors re-examine Fermi data using cuts on an event parameter to improve gamma-ray maps and more easily separate components. They find the GeV excess is robust and well-fit by a 36-51 GeV dark matter particle annihilating to bottom quarks with a cross section of 1-3×10−26 cm3/s. The signal extends over 10 degrees from the Galactic Center and is spherically symmetric, disfavoring explanations from millisecond pulsars or gas interactions.
Measuring solar radius_from_space_during_the_2003_2006_mercury_transitsSérgio Sacani
This document describes measurements of the solar radius taken from images of the 2003 and 2006 transits of Mercury captured by the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory. The authors measured contact times between Mercury and the solar limb to an accuracy of 0.09 arcseconds, finding a solar radius of 960”.12 ± 0”.09 or 696,342 ± 65km. This value is consistent between the two transits and after accounting for systematic effects between different instrument focus settings. The measurements represent some of the most accurate to date due to being taken from space above the Earth's atmosphere.
Fifteen years of_xmm_newton_and_chandra_monitoring_of_sgr_a_evidence_for_a_re...Sérgio Sacani
Três telescópios de raios-X têm monitorado o buraco negro supermassivo no centro da Via Láctea, na última década e meia observando o seu comportamento. Essa longa campanha de monitoramento tem revelado algumas novas mudanças nos padrões desse buraco negro de 4 milhões de massas solares conhecido como Sagittarius A* (Sgr A*).
O painel inferior do gráfico principal desse post é uma visão da região ao redor do Sgr A*, onde as cores vermelha, verde e azul, representam os raios-X de baixa, média e alta energia detectados pelo Observatório de Raios-X Chandra da NASA. O Sgr A* não é visto na imagem, mas ele está mergulhado no ponto brando na ponta final da seta. Os outros dois telescópios envolvidos nessas observações de raios-X de 15 anos foram o XMM-Newton da ESA e o Swift Gamma Ray Burst Explorer da NASA, mas seus dados não estão incluídos nessa imagem.
Dentro do último ano, o buraco negro normalmente tranquilo, tem mostrado um aumento no nível de flares de raios-X com relação à sua taxa típica. Esse aumento nos flares de raios-X coincide com a passagem perto do Sgr A* do misterioso objeto chamado G2. Os astrônomos estão rastreando o G2 por anos, pensado originalmente como uma extensa nuvem de gás e poeira. Contudo, depois da passagem próxima do Sgr A* no final de 2013 sua aparência não mudou muito, a menos do fato de ter sido levemente estirado pela gravidade do buraco negro. Isso levou a novas teorias que o G2 não era uma nuvem de gás, mas uma estrela ou um par de estrelas dentro de um casulo empoeirado.
Young remmants of_type_ia_supernovae_and_their_progenitors_a_study_of_snr_g19_03Sérgio Sacani
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as
standardizable candles to measure the accelerating expansion of the Universe. Yet, their progenitors
remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon
reaching close to the Chandrasekhar limit, by either steadily accreting mass from a companion star
or violently merging with another degenerate star. We show that circumstellar interaction in young
Galactic supernova remnants can be used to distinguish between these single and double degenerate
progenitor scenarios. Here we propose a new diagnostic, the Surface Brightness Index, which can
be computed from theory and compared with Chandra and VLA observations. We use this method
to demonstrate that a double degenerate progenitor can explain the decades-long
ux rise and size
increase of the youngest known Galactic SNR G1.9+0.3. We disfavor a single degenerate scenario.
We attribute the observed properties to the interaction between a steep ejecta prole and a constant
density environment. We suggest using the upgraded VLA to detect circumstellar interaction in
the remnants of historical Type Ia supernovae in the Local Group of galaxies. This may settle the
long-standing debate over their progenitors.
Subject headings: ISM: supernova remnants | radio continuum: general | X-rays: general | bi-
naries: general | circumstellar matter | supernovae: general | ISM: individual
objects(SNR G1.9+0.3)
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
The document summarizes new Chandra and HST observations of the X-ray source IC 10 X-1 located in the nearby galaxy IC 10. The observations confirm that IC 10 X-1 has an average X-ray luminosity of 1.5 × 1038 erg s-1 and is strongly variable. The position of IC 10 X-1, within 0.23 arcseconds, matches the location of the Wolf-Rayet star [MAC92] 17A in IC 10. The observations suggest IC 10 X-1 may be a rare Wolf-Rayet black hole binary system, based on its luminosity, variability, and association with the Wolf-Rayet star.
This document summarizes observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
The open cluster_ngc6520_and_the_nearby_dark_molecular_cloud_barnard_86Sérgio Sacani
This document presents optical photometry and CO observations of the open cluster NGC 6520 and nearby dark molecular cloud Barnard 86. Analysis of the optical data finds the cluster radius is 1.0±0.5 arcmin, smaller than previous estimates. The cluster age is estimated to be 150±50 Myr with reddening of EB−V =0.42±0.10. The distance from the Sun is estimated to be 1900±100 pc, larger than previous estimates. CO observations are used to derive basic properties of Barnard 86 under the assumption it lies at the same distance as the cluster.
The atacama cosmology_telescope_measuring_radio_galaxy_bias_through_cross_cor...Sérgio Sacani
A radiação cósmica de micro-ondas aponta para a matéria escura invisível, marcando o ponto onde jatos de material viajam a velocidades próximas da velocidade da luz, de acordo com uma equipe internacional de astrônomos. O principal autor do estudo, Rupert Allison da Universidade de Oxford apresentou os resultados no dia 6 de Julho de 2015 no National Astronomy Meeting em Venue Cymru, em Llandudno em Wales.
Atualmente, ninguém sabe ao certo do que a matéria escura é feita, mas ela é responsável por cerca de 26% do conteúdo de energia do universo, com galáxias massivas se formando em densas regiões de matéria escura. Embora invisível, a matéria escura se mostra através do efeito gravitacional – uma grande bolha de matéria escura puxa a matéria normal (como elétrons, prótons e nêutrons) através de sua própria gravidade, eventualmente se empacotando conjuntamente para criar as estrelas e galáxias inteiras.
Muitas das maiores dessas são galáxias ativas com buracos negros supermassivos em seus centros. Alguma parte do gás caindo diretamente na direção do buraco negro é ejetada como jatos de partículas e radiação. As observações feitas com rádio telescópios mostram que esses jatos as vezes se espalham por milhões de anos-luz desde a galáxia – mais distante até mesmo do que a extensão da própria galáxia.
Os cientistas esperam que os jatos possam viver em regiões onde existe um excesso de concentração da matéria escura, maior do que o da média. Mas como a matéria escura é invisível, testar essa ideia não é algo tão direto.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Fox m quantum_optics_an_introduction_photon antibunching1Gabriel O'Brien
This chapter discusses photon antibunching and the Hanbury Brown-Twiss experiments which helped develop modern quantum optics. It introduces the second-order correlation function g(2)(τ) which can be used to classify light as antibunched, coherent, or bunched. The chapter then discusses how the Hanbury Brown-Twiss experiments measured intensity fluctuations in light beams and how this led to defining g(2)(τ). It explores how g(2)(τ) can take different values for classical versus quantum light, with antibunched light only possible due to quantum effects.
Laser trapped mirrors could enable the construction of large, lightweight optical systems in space. A laser traps microscopic particles at the interference fringes created by its reflection between two deflectors, arranging the particles into a reflective mirror surface. Key challenges include maintaining the trap against particle evaporation from infrared background photons and understanding optical binding forces between particles. Further experiments and simulations are needed to evaluate particle design, collective behavior, trap loading and damping mechanisms to develop this technology.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
Detection of visible light from the darkest worldSérgio Sacani
This document reports the detection of visible light from the exoplanet TrES-2b using Kepler photometry data. The analysis finds a day-night contrast amplitude of 6.5 ± 1.9 parts per million, representing the lowest amplitude orbital phase variation discovered. This signal is detected at a confidence level of 99.98% and persists across different models of the data, appearing robust. If interpreted as scattering, it corresponds to a geometric albedo of 0.0253±0.0072 for TrES-2b, making it the darkest exoplanet detected so far. However, models indicate significant day-side emission, implying an even lower true albedo.
Too much pasta_for_pulsars_to_spin_downSérgio Sacani
This document summarizes a study investigating why no isolated X-ray pulsars have been observed with spin periods longer than 12 seconds. The researchers suggest this is due to a highly resistive layer in the inner crust of neutron stars, which is expected to be in a state called "nuclear pasta". Nuclear pasta has an irregular structure that increases electrical resistivity, limiting the spin-down of pulsars. Modeling the long-term magnetic field evolution incorporating a resistive nuclear pasta layer successfully reproduced the observed 12 second period limit. The results provide the first potential observational evidence for the existence of nuclear pasta in neutron star crusts.
The document summarizes two Chandra X-ray observations of the Type IIn supernova SN 2010jl taken around two months and one year after explosion. The first observation revealed a high temperature (10 keV) and very high absorption column density (1024 cm-2) from circumstellar matter. The second observation, one year later, showed the absorption column had decreased by a factor of three as expected from shock propagation. Both observations detected an unabsorbed luminosity of 7×1041 erg s-1. The Fe line detected in the first observation was not present in the second.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of
the 870 m continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that
trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal
a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli
(1{6AU) with modest contrasts (5{30%). We associate these features with concentrations of solids
that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima.
No signicant non-axisymmetric structures are detected. Some of the observed features occur near
temperatures that may be associated with the condensation fronts of major volatile species, but the
relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the
so-called zonal
ows). Other features, particularly a narrow dark annulus located only 1 AU from the
star, could indicate interactions between the disk and young planets. These data signal that ordered
substructures on AU scales can be common, fundamental factors in disk evolution, and that high
resolution microwave imaging can help characterize them during the epoch of planet formation.
Keywords: protoplanetary disks | planet-disk interactions | stars: individual (TW Hydrae)
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
This document analyzes the gamma-ray signal from the central Milky Way that is consistent with emission from annihilating dark matter particles. The authors re-examine Fermi data using cuts on an event parameter to improve gamma-ray maps and more easily separate components. They find the GeV excess is robust and well-fit by a 36-51 GeV dark matter particle annihilating to bottom quarks with a cross section of 1-3×10−26 cm3/s. The signal extends over 10 degrees from the Galactic Center and is spherically symmetric, disfavoring explanations from millisecond pulsars or gas interactions.
Measuring solar radius_from_space_during_the_2003_2006_mercury_transitsSérgio Sacani
This document describes measurements of the solar radius taken from images of the 2003 and 2006 transits of Mercury captured by the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory. The authors measured contact times between Mercury and the solar limb to an accuracy of 0.09 arcseconds, finding a solar radius of 960”.12 ± 0”.09 or 696,342 ± 65km. This value is consistent between the two transits and after accounting for systematic effects between different instrument focus settings. The measurements represent some of the most accurate to date due to being taken from space above the Earth's atmosphere.
Fifteen years of_xmm_newton_and_chandra_monitoring_of_sgr_a_evidence_for_a_re...Sérgio Sacani
Três telescópios de raios-X têm monitorado o buraco negro supermassivo no centro da Via Láctea, na última década e meia observando o seu comportamento. Essa longa campanha de monitoramento tem revelado algumas novas mudanças nos padrões desse buraco negro de 4 milhões de massas solares conhecido como Sagittarius A* (Sgr A*).
O painel inferior do gráfico principal desse post é uma visão da região ao redor do Sgr A*, onde as cores vermelha, verde e azul, representam os raios-X de baixa, média e alta energia detectados pelo Observatório de Raios-X Chandra da NASA. O Sgr A* não é visto na imagem, mas ele está mergulhado no ponto brando na ponta final da seta. Os outros dois telescópios envolvidos nessas observações de raios-X de 15 anos foram o XMM-Newton da ESA e o Swift Gamma Ray Burst Explorer da NASA, mas seus dados não estão incluídos nessa imagem.
Dentro do último ano, o buraco negro normalmente tranquilo, tem mostrado um aumento no nível de flares de raios-X com relação à sua taxa típica. Esse aumento nos flares de raios-X coincide com a passagem perto do Sgr A* do misterioso objeto chamado G2. Os astrônomos estão rastreando o G2 por anos, pensado originalmente como uma extensa nuvem de gás e poeira. Contudo, depois da passagem próxima do Sgr A* no final de 2013 sua aparência não mudou muito, a menos do fato de ter sido levemente estirado pela gravidade do buraco negro. Isso levou a novas teorias que o G2 não era uma nuvem de gás, mas uma estrela ou um par de estrelas dentro de um casulo empoeirado.
Young remmants of_type_ia_supernovae_and_their_progenitors_a_study_of_snr_g19_03Sérgio Sacani
Type Ia supernovae, with their remarkably homogeneous light curves and spectra, have been used as
standardizable candles to measure the accelerating expansion of the Universe. Yet, their progenitors
remain elusive. Common explanations invoke a degenerate star (white dwarf) which explodes upon
reaching close to the Chandrasekhar limit, by either steadily accreting mass from a companion star
or violently merging with another degenerate star. We show that circumstellar interaction in young
Galactic supernova remnants can be used to distinguish between these single and double degenerate
progenitor scenarios. Here we propose a new diagnostic, the Surface Brightness Index, which can
be computed from theory and compared with Chandra and VLA observations. We use this method
to demonstrate that a double degenerate progenitor can explain the decades-long
ux rise and size
increase of the youngest known Galactic SNR G1.9+0.3. We disfavor a single degenerate scenario.
We attribute the observed properties to the interaction between a steep ejecta prole and a constant
density environment. We suggest using the upgraded VLA to detect circumstellar interaction in
the remnants of historical Type Ia supernovae in the Local Group of galaxies. This may settle the
long-standing debate over their progenitors.
Subject headings: ISM: supernova remnants | radio continuum: general | X-rays: general | bi-
naries: general | circumstellar matter | supernovae: general | ISM: individual
objects(SNR G1.9+0.3)
Periodic mass extinctions_and_the_planet_x_model_reconsideredSérgio Sacani
The 27 Myr periodicity in the fossil extinction record has been con-
firmed in modern data bases dating back 500 Myr, which is twice the time
interval of the original analysis from thirty years ago. The surprising regularity
of this period has been used to reject the Nemesis model. A second
model based on the sun’s vertical galactic oscillations has been challenged
on the basis of an inconsistency in period and phasing. The third astronomical
model originally proposed to explain the periodicity is the Planet
X model in which the period is associated with the perihelion precession
of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated
to mass extinctions, a trans-Neptunian super-Earth planet has been proposed
to explain the observation that the inner Oort cloud objects Sedna
and 2012VP113 have perihelia that lie near the ecliptic plane. In this
Letter we reconsider the Planet X model in light of the confluence of the
modern palaeontological and outer solar system dynamical evidence.
Key Words: astrobiology - planets and satellites - Kuiper belt:
general - comets: general
The document summarizes new Chandra and HST observations of the X-ray source IC 10 X-1 located in the nearby galaxy IC 10. The observations confirm that IC 10 X-1 has an average X-ray luminosity of 1.5 × 1038 erg s-1 and is strongly variable. The position of IC 10 X-1, within 0.23 arcseconds, matches the location of the Wolf-Rayet star [MAC92] 17A in IC 10. The observations suggest IC 10 X-1 may be a rare Wolf-Rayet black hole binary system, based on its luminosity, variability, and association with the Wolf-Rayet star.
This document summarizes observations of the debris disk around the subgiant star κ CrB using Herschel and Keck. Herschel spatially resolved images of the debris disk, the first such images of a disk around a subgiant star. Keck radial velocity monitoring provided evidence for a second planetary companion around κ CrB. Keck adaptive optics imaging placed an upper limit on the mass of this companion. Modeling of the Herschel images showed the dust is broadly distributed but could not distinguish between a single wide belt or two narrow belts. The observations are consistent with dynamical depletion or collisional erosion clearing the inner regions of the disk.
X ray emission-from_strongly_asymmetric_circumstellar_material_in_the_remnant...Sérgio Sacani
This document summarizes a study of X-ray emission from circumstellar material (CSM) in the remnant of Kepler's supernova. The researchers used a statistical technique to isolate X-ray emission from CSM versus ejecta based on spectral characteristics. They found that most CSM is distributed along the bright north rim, but substantial amounts are also projected against the center, indicating a disk-like distribution of CSM from the progenitor system before the supernova. Hydrodynamic simulations support an AGB star companion as the origin of the asymmetric CSM. Quantitative analysis of magnesium emission identifies CSM and requires Kepler to have originated from a close binary system.
The open cluster_ngc6520_and_the_nearby_dark_molecular_cloud_barnard_86Sérgio Sacani
This document presents optical photometry and CO observations of the open cluster NGC 6520 and nearby dark molecular cloud Barnard 86. Analysis of the optical data finds the cluster radius is 1.0±0.5 arcmin, smaller than previous estimates. The cluster age is estimated to be 150±50 Myr with reddening of EB−V =0.42±0.10. The distance from the Sun is estimated to be 1900±100 pc, larger than previous estimates. CO observations are used to derive basic properties of Barnard 86 under the assumption it lies at the same distance as the cluster.
The atacama cosmology_telescope_measuring_radio_galaxy_bias_through_cross_cor...Sérgio Sacani
A radiação cósmica de micro-ondas aponta para a matéria escura invisível, marcando o ponto onde jatos de material viajam a velocidades próximas da velocidade da luz, de acordo com uma equipe internacional de astrônomos. O principal autor do estudo, Rupert Allison da Universidade de Oxford apresentou os resultados no dia 6 de Julho de 2015 no National Astronomy Meeting em Venue Cymru, em Llandudno em Wales.
Atualmente, ninguém sabe ao certo do que a matéria escura é feita, mas ela é responsável por cerca de 26% do conteúdo de energia do universo, com galáxias massivas se formando em densas regiões de matéria escura. Embora invisível, a matéria escura se mostra através do efeito gravitacional – uma grande bolha de matéria escura puxa a matéria normal (como elétrons, prótons e nêutrons) através de sua própria gravidade, eventualmente se empacotando conjuntamente para criar as estrelas e galáxias inteiras.
Muitas das maiores dessas são galáxias ativas com buracos negros supermassivos em seus centros. Alguma parte do gás caindo diretamente na direção do buraco negro é ejetada como jatos de partículas e radiação. As observações feitas com rádio telescópios mostram que esses jatos as vezes se espalham por milhões de anos-luz desde a galáxia – mais distante até mesmo do que a extensão da própria galáxia.
Os cientistas esperam que os jatos possam viver em regiões onde existe um excesso de concentração da matéria escura, maior do que o da média. Mas como a matéria escura é invisível, testar essa ideia não é algo tão direto.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
Studies of ngc_6720_with_calibrated_hst_wfc3_emission_line_filter_imagesSérgio Sacani
This study uses calibrated Hubble Space Telescope images of the Ring Nebula (NGC 6720) taken 12.925 years apart to measure tangential motions within the nebula. Individual features were measured in nitrogen emission line images as well as dark knots seen against oxygen emission. The results indicate that the nebula is expanding homologously, but at a faster rate along its major axis. Dark knots were found to expand more slowly than the nebular gas. The tangential motion measurements allow estimates of the nebula's distance and dynamic age to be about 720 pc and 4000 years, respectively.
We discovered two transient events in the Kepler eld with light curves that strongly suggest they
are type II-P supernovae. Using the fast cadence of the Kepler observations we precisely estimate
the rise time to maximum for KSN2011a and KSN2011d as 10.50:4 and 13.30:4 rest-frame days
respectively. Based on ts to idealized analytic models, we nd the progenitor radius of KSN2011a
(28020 R) to be signicantly smaller than that for KSN2011d (49020 R) but both have similar
explosion energies of 2.00:3 1051 erg.
The rising light curve of KSN2011d is an excellent match to that predicted by simple models of
exploding red supergiants (RSG). However, the early rise of KSN2011a is faster than the models
predict possibly due to the supernova shockwave moving into pre-existing wind or mass-loss from the
RSG. A mass loss rate of 10 4 M yr 1 from the RSG can explain the fast rise without impacting
the optical
ux at maximum light or the shape of the post-maximum light curve.
No shock breakout emission is seen in KSN2011a, but this is likely due to the circumstellar inter-
action suspected in the fast rising light curve. The early light curve of KSN2011d does show excess
emission consistent with model predictions of a shock breakout. This is the rst optical detection of
a shock breakout from a type II-P supernova.
Inverse Compton cooling limits the brightness temperature of the radiating plasma to a maximum of
1011.5 K. Relativistic boosting can increase its observed value, but apparent brightness temperatures
much in excess of 1013 K are inaccessible using ground-based very long baseline interferometry (VLBI)
at any wavelength. We present observations of the quasar 3C 273, made with the space VLBI mission
RadioAstron on baselines up to 171,000 km, which directly reveal the presence of angular structure as
small as 26 µas (2.7 light months) and brightness temperature in excess of 1013 K. These measurements
challenge our understanding of the non-thermal continuum emission in the vicinity of supermassive
black holes and require a much higher Doppler factor than what is determined from jet apparent
kinematics.
Keywords: galaxies: active — galaxies: jets — radio continuum: galaxies — techniques: interferometric
— quasars: individual (3C 273)
Fox m quantum_optics_an_introduction_photon antibunching1Gabriel O'Brien
This chapter discusses photon antibunching and the Hanbury Brown-Twiss experiments which helped develop modern quantum optics. It introduces the second-order correlation function g(2)(τ) which can be used to classify light as antibunched, coherent, or bunched. The chapter then discusses how the Hanbury Brown-Twiss experiments measured intensity fluctuations in light beams and how this led to defining g(2)(τ). It explores how g(2)(τ) can take different values for classical versus quantum light, with antibunched light only possible due to quantum effects.
Laser trapped mirrors could enable the construction of large, lightweight optical systems in space. A laser traps microscopic particles at the interference fringes created by its reflection between two deflectors, arranging the particles into a reflective mirror surface. Key challenges include maintaining the trap against particle evaporation from infrared background photons and understanding optical binding forces between particles. Further experiments and simulations are needed to evaluate particle design, collective behavior, trap loading and damping mechanisms to develop this technology.
Artigo relata como a Terra sofreu com os impactos de ateroides a 4 bilhões de anos atrás, e como a superfície do planeta foi remodelada e os oceanos formados.
This document summarizes a detonating failed deflagration model of Type Ia supernovae. The model involves an off-center deflagration in a massive white dwarf that fails to unbind the star. Disturbances from the failed deflagration pollute the stellar surface and eventually evolve into isolated shock regions, serving as ignition points for detonations that result in supernova explosion. Preliminary results show ejecta composed of silicon and iron group elements, with an inner egg-shaped region surrounded by an incomplete burning shell. Explosion energies are around 1.3-1.5×1051 erg.
Propagation of highly_efficient_star_formation_in_ngc7000Sérgio Sacani
This document summarizes a study of star formation in molecular clouds near the H II region NGC 7000. The authors surveyed NH3 and H2O maser emission toward the molecular cloud L935 located near NGC 7000. They identified five dense molecular clumps based on NH3 emission, which have similar gas temperatures but different levels of star formation activity. One clump located near the boundary of the H II region has a high star formation efficiency of 36-62%, suggesting triggered star formation due to its interaction with the expanding H II region.
Alma observations of_feeding_and_feedback_in_nearby_seyfert_galaxies_outflow_...Sérgio Sacani
ALMA observations of the Seyfert 2 galaxy NGC 1433 reveal a nuclear gaseous spiral structure within a nuclear ring encircling a nuclear stellar bar. Near the nucleus, there is intense high-velocity CO emission interpreted as an AGN-driven molecular outflow. The outflow involves a molecular mass of 3.6 million solar masses and a flow rate of about 7 solar masses per year. Continuum emission at the center is likely thermal dust emission from a molecular torus expected in this Seyfert 2 galaxy. The observations probe gas dynamics within 24 parsecs of the active galactic nucleus.
An unindetified line_in_xray_spectra_of_the_adromeda_galaxy_and_perseus_galax...Sérgio Sacani
This document summarizes an analysis of X-ray spectra from the Andromeda galaxy and Perseus galaxy cluster observed with the XMM-Newton X-ray observatory. The analysis identified a weak unidentified line at an energy of approximately 3.5 keV in the spectra of both objects. The line strength increases towards the centers of the objects and is stronger in Perseus than in Andromeda. The line properties are consistent with originating from the decay of dark matter particles, though an instrumental or astrophysical source cannot be ruled out based on individual objects. Future detections or non-detections in additional targets could help reveal the nature of this line.
Results from telescope_array_experimentSérgio Sacani
The Telescope Array (TA) experiment studies ultrahigh energy cosmic rays using a hybrid detector consisting of a surface detector and three fluorescence detector stations. This paper reports three results from TA:
1) The cosmic ray spectrum measured by the surface detector shows an ankle feature and a 3.5 sigma suppression at the expected GZK cutoff energy, consistent with the HiRes experiment.
2) Measurement of the average shower maximum depth with the fluorescence detectors indicates a light composition, most likely protons.
3) A search for correlations between surface detector events and Active Galactic Nuclei found no significant correlations, consistent with results from HiRes.
Xray and protostars_in_the_trifid_nebulaSérgio Sacani
The document summarizes X-ray observations of the Trifid Nebula using ROSAT and ASCA. ROSAT images revealed around a dozen X-ray sources in the nebula, including the bright O7 star HD 164492 that provides much of the ionization. Ten X-ray sources were correlated with near-infrared sources identified as young stars or protostars. ASCA spectroscopy of the brightest source showed hard X-ray emission up to 10 keV including an iron K line, best fit with a two-temperature thermal model and absorption. The hotter component's temperature is unusually high and may originate from interaction with another object or protostellar flares.
The birth of_a_galaxy_propelling_reionisation_with_the_faintest_galaxiesSérgio Sacani
This document summarizes a study that uses cosmological radiation hydrodynamics simulations to model dwarf galaxy formation and properties at z > 7. The study finds that metal-enriched star formation can occur in halos down to masses of ~106 M, especially in neutral regions, and that these smallest galaxies provide nearly 30% of the ionizing photon budget needed for reionization despite only hosting up to 104 M of stars. The study also finds that the galaxy luminosity function flattens above MUV = -12 at z = 10 and that the fraction of ionizing radiation escaping into the intergalactic medium decreases from 50% to 5% over the halo mass range of log M/M⊙ = 7.0-8.
Detection of an_unindentified_emission_line_in_the_stacked_x_ray_spectrum_of_...Sérgio Sacani
1. Researchers detected a previously unknown emission line in the stacked X-ray spectrum of 73 galaxy clusters observed by XMM-Newton. 2. The line was detected at an energy of 3.55-3.57 keV and was seen independently in subsamples of clusters. 3. The line was also detected in Chandra observations of the Perseus cluster but not in observations of the Virgo cluster. 4. The nature of this line is unclear - it could be a thermal line from an undetected element, or potentially the decay line of a hypothesized dark matter particle called a sterile neutrino. Further observations are needed to determine the origin of the line.
This pilot survey used modest aperture telescopes to image 8 nearby spiral galaxies in order to search for stellar tidal streams. Ultra-deep imaging revealed 6 previously undetected extensive (up to 30 kpc) stellar structures likely from tidally disrupted satellites. A diversity of tidal feature morphologies was found, including great circle-like streams, remote shells, and jets emerging from disks. Simulations predict tidal debris should be common and match the observed variety, providing evidence minor mergers have shaped disk galaxies since z=1.
This document summarizes observations of rapid dust formation in the luminous supernova SN 2010jl over multiple epochs from 26 to 868 days past peak brightness. Analysis of emission line profiles shows increasing extinction over time, indicating continuous dust formation. The extinction curve implies the presence of very large (>1 micron) dust grains. Thermal emission models suggest dust temperatures declining from 2300K to 1100K over time, requiring carbonaceous rather than silicate dust. Combined extinction and emission data indicate a dust mass of ~0.0025 solar masses at 868 days, growing rapidly and expected to reach ~0.5 solar masses by 8000 days if production continues. The rapid formation of large dust grains suggests an efficient mechanism for dust nucle
Kinematics and simulations_of_the_stellar_stream_in_the_halo_of_the_umbrella_...Sérgio Sacani
This document summarizes a study of the stellar stream and substructures around the Umbrella Galaxy (NGC 4651). Deep imaging and spectroscopy were used to characterize the properties and kinematics of the stream. Tracer objects like globular clusters and planetary nebulae were identified and found to delineate a kinematically cold feature in position-velocity space. Dynamical modeling suggests the stream originated from the tidal disruption of a dwarf galaxy on a highly eccentric orbit about 6-10 billion years ago. This work demonstrates the feasibility of using discrete tracers to recover the kinematics and model the dynamics of low surface brightness stellar streams around distant galaxies.
This document summarizes the detection of a super-Earth planet orbiting the star GJ 832. Radial velocity data from three telescopes revealed a planet, GJ 832c, with an orbital period of 35.68 days and a minimum mass of 5.4 Earth masses. GJ 832c has a low eccentricity orbit of 0.18 near the inner edge of the star's habitable zone. However, given its large mass, the planet likely has a massive atmosphere that could render it uninhabitable. The GJ 832 system resembles a miniature version of our solar system, with an interior potentially rocky planet and a distant gas giant.
This document presents observations from the VLT X-shooter instrument of two quasars, SDSS J1106+1939 and SDSS J1512+1119. For SDSS J1106+1939, a broad absorption line (BAL) outflow is detected with a kinetic luminosity of at least 10^46 erg/s, which is 5% of the quasar's bolometric luminosity. This outflow has a velocity of ~8000 km/s and is located ~300 pc from the quasar. For SDSS J1512+1119, two separate outflows are detected using the same technique, with distances ranging from 100-2000 pc from the central source. The distances of the outflows
A magnetar-powered X-ray transient as the aftermath of a binary neutron-star ...Sérgio Sacani
Mergers of neutron stars are known to be associated with short γ-ray
bursts1–4
. If the neutron-star equation of state is sufficiently stiff
(that is, the pressure increases sharply as the density increases), at
least some such mergers will leave behind a supramassive or even a
stable neutron star that spins rapidly with a strong magnetic field5–8
(that is, a magnetar). Such a magnetar signature may have been
observed in the form of the X-ray plateau that follows up to half
of observed short γ-ray bursts9,10. However, it has been expected
that some X-ray transients powered by binary neutron-star mergers
may not be associated with a short γ-ray burst11,12. A fast X-ray
transient (CDF-S XT1) was recently found to be associated with a
faint host galaxy, the redshift of which is unknown13. Its X-ray and
host-galaxy properties allow several possible explanations including
a short γ-ray burst seen off-axis, a low-luminosity γ-ray burst at
high redshift, or a tidal disruption event involving an intermediatemass black hole and a white dwarf13. Here we report a second X-ray
transient, CDF-S XT2, that is associated with a galaxy at redshift
z = 0.738 (ref. 14). The measured light curve is fully consistent with
the X-ray transient being powered by a millisecond magnetar. More
intriguingly, CDF-S XT2 lies in the outskirts of its star-forming host
galaxy with a moderate offset from the galaxy centre, as short γ-ray
bursts often do15,16. The estimated event-rate density of similar
X-ray transients, when corrected to the local value, is consistent
with the event-rate density of binary neutron-star mergers that is
robustly inferred from the detection of the gravitational-wave event
GW170817.
This paper presents a study of the extended X-ray emission in the Seyfert galaxy NGC 4151 using deep Chandra observations. Key findings include:
1) Emission line maps show strong OVII, OVIII, and NeIX line emission extending along the northeast-southwest direction, consistent with an ionization cone.
2) Spectral analysis finds the extended emission is well described by photoionized plasma models, supporting a dominant role for nuclear photoionization.
3) Faint extended emission is also seen perpendicular to the ionization cone, indicating some leakage of nuclear ionizing radiation through warm absorbers rather than being blocked by an obscuring torus.
This document summarizes observations of the exoplanet HD 189733b taken with Chandra and XMM-Newton telescopes. The observations detected X-ray emissions from both the planet-hosting star HD 189733A and its companion star HD 189733B. A transit of HD 189733b in front of its star was detected in soft X-rays, with a transit depth of 6-8% compared to 2.41% in the optical. This is interpreted as evidence for an extended atmosphere around the planet that is opaque to X-rays but transparent at optical wavelengths. The magnetic activity of the companion star HD 189733B was also found to be inconsistent with the activity of the planet-hosting star, possibly due to
The nustar extragalactic_survey_a_first_sensitive_lookSérgio Sacani
The document summarizes the first ten sources detected by the Nuclear Spectroscopic Telescope Array (NuSTAR) as part of its extragalactic survey. NuSTAR provides the first sensitive census of the cosmic X-ray background source population at energies above 10 keV. The ten sources have a broad range of redshifts and luminosities, with a median redshift of 0.7 and luminosity of 3×10^44 erg/s. Based on broad-band spectroscopy and SED analysis, the dominant population is quasars with luminosities above 10^44 erg/s, of which around 50% are obscured. However, none are Compton thick and the fraction of Compton thick quasars is constrained to
Dust in the_polar_region_as_a_major_contributor_to_the_infrared_emission_of_a...Sérgio Sacani
The mid-infrared emission of the active galactic nucleus NGC 3783 was observed using interferometry over multiple epochs, providing dense coverage of position angles and baselines. The emission was found to be strongly elongated along a position angle of -52 degrees, closely aligned with the polar axis orientation of -45 degrees. The half-light radii were measured to be 20.0 mas by 6.7 mas, corresponding to an axis ratio of 3:1. This implies that 60-90% of the 8-13 micron emission is from the polar-elongated component. The observations support a scenario where the majority of mid-infrared emission in Seyfert galaxies originates from a dusty wind in the polar region,
Detection of an atmosphere around the super earth 55 cancri eSérgio Sacani
We report the analysis of two new spectroscopic observations of the super-Earth 55 Cancri e, in the near
infrared, obtained with the WFC3 camera onboard the HST. 55 Cancri e orbits so close to its parent
star, that temperatures much higher than 2000 K are expected on its surface. Given the brightness
of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length
and a very high scanning speed. We use our specialized pipeline to take into account systematics
introduced by these observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average relative uncertainty
of 22 ppm per visit and nd modulations that depart from a straight line model with a 6 condence
level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T -REx, has identied HCN to be the
most likely molecular candidate able to explain the features at 1.42 and 1.54 m. While additional
spectroscopic observations in a broader wavelength range in the infrared will be needed to conrm
the HCN detection, we discuss here the implications of such result. Our chemical model, developed
with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a
high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic
than previously thought.
This document summarizes VLBI observations of supernova SN 2011dh made 14 days after its discovery, providing the earliest radio image of a supernova. The observations detected SN 2011dh at 22 GHz using a subset of the EVN array. The recovered flux density was approximately half the value measured by the EVLA at the same frequency and epoch, possibly due to extended emission or calibration issues. Precise coordinates for SN 2011dh were determined, linked to the ICRF, which may help improve future VLBI observations of the supernova.
The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in...Sérgio Sacani
SMSS J114447.77-430859.3 (z = 0.83) has been identified in the SkyMapper Southern Survey as the most luminous quasar in
the last ∼ 9 Gyr . In this paper, we report on the eROSITA/Spectrum–Roentgen–Gamma (SRG) observations of the source from
the eROSITA All Sky Survey, along with presenting results from recent monitoring performed using Swift, XMM-Newton, and
NuSTAR. The source shows a clear variability by factors of ∼10 and ∼2.7 overtime-scales of a year and of a few days,respectively.
When fit with an absorbed power law plus high-energy cutoff, the X-ray spectra reveal a = 2.2 ± 0.2 and Ecut = 23+26
−5 keV
. Assuming Comptonization, we estimate a coronal optical depth and electron temperature of τ = 2.5 − 5.3 (5.2 − 8) and
kT = 8 − 18 (7.5 − 14) keV , respectively, for a slab (spherical) geometry. The broadband SED is successfully modelled by
assuming either a standard accretion disc illuminated by a central X-ray source, or a thin disc with a slim disc emissivity profile.
The former model results in a black hole mass estimate of the order of 1010 M , slightly higher than prior optical estimates;
meanwhile, the latter model suggests a lower mass. Both models suggest sub-Eddington accretion when assuming a spinning
black hole, and a compact (∼ 10 rg ) X-ray corona. The measured intrinsic column density and the Eddington ratio strongly
suggest the presence of an outflow driven by radiation pressure. This is also supported by variation of absorption by an order of
magnitude over the period of ∼ 900 d .
A spectroscopic sample_of_massive_galaxiesSérgio Sacani
This document describes a study of 16 massive galaxies at z ~ 2 selected from the 3D-HST spectroscopic survey based on the detection of a strong 4000 Angstrom break in their spectra. Spectroscopy and imaging from HST/WFC3 are used to determine accurate redshifts, stellar population properties, and structural parameters. The sample significantly increases the number of spectroscopically confirmed evolved galaxies at z ~ 2 with robust size measurements. The analysis populates the mass-size relation and finds it is consistent with local relations but with smaller sizes by a factor of 2-3. A model is presented where the observed size evolution is explained by quenching of increasingly larger star-forming galaxies at a rate set by
Solving the Multimessenger Puzzle of the AGN-starburst Composite Galaxy NGC 1068Sérgio Sacani
Multiwavelength observations indicate that some starburst galaxies show a dominant nonthermal contribution from
their central region. These active galactic nuclei (AGN)-starburst composites are of special interest, as both
phenomena on their own are potential sources of highly energetic cosmic rays and associated γ-ray and neutrino
emission. In this work, a homogeneous, steady-state two-zone multimessenger model of the nonthermal emission
from the AGN corona as well as the circumnuclear starburst region is developed and subsequently applied to the
case of NGC 1068, which has recently shown some first indications of high-energy neutrino emission. Here, we
show that the entire spectrum of multimessenger data—from radio to γ-rays including the neutrino constraint—can
be described very well if both, starburst and AGN corona, are taken into account. Using only a single emission
region is not sufficient.
A close pair_binary_in_a_distant_triple_supermassive_black_hole_systemSérgio Sacani
This document reports the discovery of a triple supermassive black hole system through radio observations. Very Long Baseline Interferometry observations revealed two flat-spectrum radio cores, labelled J1502SE and J1502SW, within the galaxy J1502S, separated by about 140 parsecs. Analysis of archival data provides further evidence of this close black hole pair through the detection of 'S-shaped' radio emission between the two cores, indicative of jet precession caused by the binary black holes. This is the closest black hole pair yet discovered and demonstrates a new method for finding binary black holes that cannot be spatially resolved with current instruments.
M82 X-2 is the first pulsating ultraluminous X-ray source discovered. The luminosity of these extreme pulsars, if
isotropic, implies an extreme mass transfer rate. An alternative is to assume a much lower mass transfer rate, but
with an apparent luminosity boosted by geometrical beaming. Only an independent measurement of the mass
transfer rate can help discriminate between these two scenarios. In this paper, we follow the orbit of the neutron star
for 7 yr, measure the decay of the orbit (P P orb orb 8 10 yr 6 1 · » - - - ), and argue that this orbital decay is driven by
extreme mass transfer of more than 150 times the mass transfer limit set by the Eddington luminosity. If this is true,
the mass available to the accretor is more than enough to justify its luminosity, with no need for beaming. This also
strongly favors models where the accretor is a highly magnetized neutron star.
Chandra deep observation_of_xdcpj004402033_a_massive_galaxy_cluster_at_z_1_5Sérgio Sacani
Artigo apresenta os resultados obtidos pelo Chandra ao medir com precisão a massa do mais massivo aglomerado de galáxias do universo distante, o Aglomerado Gioiello.
The puzzling source_in_ngc6388_a_possible_planetary_tidal_disruption_eventSérgio Sacani
Artigo descreve a descoberta da destruição de um planeta ao passar próximo a uma estrela do tipo anã branca presente dentro do aglomerado globular de estrelas NGC 6388. Para isso os astrônomos utilizaram um arsenal de telescópios.
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
A dwarf galaxy is colliding with the large spiral galaxy NGC 1232, as revealed by X-ray observations from Chandra. The collision is creating a large region (7.25 kpc in diameter) of shocked, hot gas with a temperature of around 5.8 million kelvin. The X-ray luminosity of this collisional aftermath is estimated to be 3.7x10^38 ergs/s. Based on the size and temperature of the X-ray emitting region, the collision likely involves a dwarf galaxy and represents a massive energy input into NGC 1232, far exceeding a typical supernova. Such collisions detected solely in X-rays may provide insights into the role of dwarf galaxy interactions in the evolution of
The hazardous km-sized NEOs of the next thousands of yearsSérgio Sacani
This document discusses methods for assessing the long-term impact risk of km-sized near-Earth objects (NEOs) over thousands of years. It analyzes the evolution of the Minimum Orbit Intersection Distance (MOID) between NEOs and Earth to identify objects that remain in close proximity for extended periods. It then estimates the probability of a deep Earth encounter during these low-MOID periods based on the growth of orbital uncertainties over time. This allows the authors to rank km-sized NEOs by their long-term impact hazard and identify targets that warrant further observation and analysis.
Similar to Non xrays from_the_very_nearby_typeia_sn_2014j_constraints_on_its_environment (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
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ملزمة تشريح الجهاز الهيكلي (نظري 3)
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تتميز هذهِ الملزمة بعِدة مُميزات :
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𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
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This presentation was provided by Racquel Jemison, Ph.D., Christina MacLaughlin, Ph.D., and Paulomi Majumder. Ph.D., all of the American Chemical Society, for the second session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session Two: 'Expanding Pathways to Publishing Careers,' was held June 13, 2024.
Andreas Schleicher presents PISA 2022 Volume III - Creative Thinking - 18 Jun...EduSkills OECD
Andreas Schleicher, Director of Education and Skills at the OECD presents at the launch of PISA 2022 Volume III - Creative Minds, Creative Schools on 18 June 2024.
Andreas Schleicher presents PISA 2022 Volume III - Creative Thinking - 18 Jun...
Non xrays from_the_very_nearby_typeia_sn_2014j_constraints_on_its_environment
1. DRAFT VERSION MAY 8, 2014
Preprint typeset using LATEX style emulateapj v. 5/2/11
NO X-RAYS FROM THE VERY NEARBY TYPE IA SN 2014J: CONSTRAINTS ON ITS ENVIRONMENT
R. MARGUTTI
1
, J. PARRENT
1
, A. KAMBLE
1
, A. M. SODERBERG
1
, R. J. FOLEY
2,3
, D. MILISAVLJEVIC
1
, M. R. DROUT
1
, R. KIRSHNER
1
Draft version May 8, 2014
ABSTRACT
Deep X-ray observations of the post-explosion environment around the very nearby Type Ia SN 2014J (dL =
3.5Mpc) reveal no X-ray emission down to a luminosity Lx < 7 × 1036
ergs−1
(0.3-10 keV) at δt ∼ 20days
after the explosion. We interpret this limit in the context of Inverse Compton emission from upscattered optical
photons by the supernova shock and constrain the pre-explosion mass-loss rate of the stellar progenitor system
to be ˙M < 10−9
M y−1
(for wind velocity vw = 100kms−1
). Alternatively, the SN shock might be expanding
into a uniform medium with density nCSM < 3cm−3
. These results rule out single-degenerate (SD) systems
with steady mass-loss until the terminal explosion and constrain the fraction of transferred material lost at the
outer Lagrangian point to be ≤ 1%. The allowed progenitors are (i) WD-WD progenitors, (ii) SD systems with
unstable hydrogen burning experiencing recurrent nova eruptions with recurrence time t < 300 yrs and (iii)
stars where the mass loss ceases before the explosion.
Subject headings: supernovae: specific (SN 2014J)
1. INTRODUCTION
Type Ia supernovae (SNe) are believed to originate from
white dwarfs (WDs) in binary systems. However, no stellar
progenitor has ever been directly identified in pre-explosion
images, not even for the two closest Type Ia SNe discovered
in the last 25 years, SN 2011fe (Li et al. 2011) and, more re-
cently, SN 2014J (Kelly et al. 2014, Goobar et al. 2014). As a
result, the nature of their progenitor system is still a matter of
debate (e.g. Howell 2011, Di Stefano et al. 2013, Maoz et al.
2013). Here we present a detailed study of SN 2014J at X-ray
energies, with the primary goal to constrain the circumstellar
environment of the exploding star.
SN 2014J was discovered by Fossey et al. (2014) in the
nearby starburst galaxy M82. At the distance of dL = 3.5Mpc
(Dalcanton et al. 2009; Karachentsev & Kashibadze 2006),
SN 2014J is the nearest Type Ia SN discovered in the last three
decades and offers an unprecedented opportunity to study the
progenitor system of thermonuclear stellar explosions.
Type Ia SNe are believed to originate from the runaway
thermonuclear explosion of a degenerate C/O stellar core,
likely a WD in a binary system (Hoyle & Fowler 1960, Col-
gate & McKee 1969, see Calder et al. 2013, Maoz et al. 2013
and Parrent et al. 2014 for recent reviews). While there is con-
sensus that a white dwarf explodes, the astronomical events
that precede the explosion are less clear.
Two progenitor channels are mostly favored, involving non-
degenerate and degenerate binary companions, respectively.
In the first scenario (single-degenerate, SD, hereafter), the
WD accretes material from the companion, potentially a gi-
ant, sub-giant or main-sequence star (Whelan & Iben 1973,
Hillebrandt & Niemeyer 2000, Nomoto 1982b). Wind from
the secondary star provides material to be accreted (symbi-
otic channel, see e.g. Patat et al. 2011). Mass can be trans-
ferred to the WD via Roche-lobe overflow (RLOF) from a
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cam-
bridge, MA 02138, USA.
2 Astronomy Department, University of Illinois at Urbana–Champaign,
1002 W. Green Street, Urbana, IL 61801 USA.
3 Department of Physics, University of Illinois Urbana–Champaign,
1110 W. Green Street, Urbana, IL 61801 USA.
hydrogen-rich mass-donor star or He star (Nomoto 1982a,
van den Heuvel et al. 1992, Iben & Tutukov 1994, Yoon &
Langer 2003). The second standard scenario involves two
WDs (double-degenerate scenario, DD, hereafter, Iben & Tu-
tukov 1984, Webbink 1984). The explosion occurs as the two
WDs merge as a consequence of the loss of angular momen-
tum.
The two classes of progenitor systems are predicted to leave
different imprints on the circumbinary environment. For SD
progenitor channels the local environment is expected to be
either directly enriched by wind from the donor star (symbi-
otic systems) or by non-conservative mass transfer (i.e. by
matter that the WD is unable to accrete). For the DD scenario
the general expectation is that of a “cleaner” environment with
density typical of the inter stellar medium (ISM). Particularly
intriguing in this respect is the evidence for interaction of the
SN ejecta with circumbinary material as revealed by optical
observations of some Type Ia SNe (see e.g. Silverman et al.
2013).
The nearby SN environment can also be revealed by us-
ing sensitive X-ray observations obtained shortly after the ex-
plosion (e.g. Russell & Immler 2012, Horesh et al. 2012,
Margutti et al. 2012). For both the SD and DD scenarios,
the X-ray emission is powered by the interaction of the SN
shock with the circumburst medium and can thus be used as
a probe of the local environment (e.g. Chevalier & Fransson
2006). Here we present the results from deep Chandra X-ray
observations of SN 2014J that enable us to put stringent con-
straints on the progenitor system mass-loss prior to explosion.
X-ray observations are described in Sec. 2. We re-construct
the bolometric light-curve of SN 2014J from broad-band op-
tical photometry spanning the UV to NIR range in Sec. 3.
We combine the optical and X-ray observations to derive a
deep limit to the mass-loss rate of the progenitor system of
SN 2014J in Sec. 4. The mass-loss limit is used to infer the
nature of the donor star in the progenitor system of SN 2014J
in Sec. 5. Conclusions are drawn in Sec. 6.
Uncertainties are quoted at 1σ confidence level, unless oth-
erwise noted. Throughout the paper we use 2014 January
14.72 UT as explosion date of SN 2014J (Zheng et al. 2014).
arXiv:1405.1488v1[astro-ph.HE]7May2014
2. 2 Margutti et al.
The possible presence of a “dark phase” (e.g. Piro & Nakar
2012, 2013) with duration between hours and a few days be-
tween the explosion and the time of the first emitted light has
no impact on our major conclusions.
2. OBSERVATIONS AND DATA ANALYSIS
2.1. Chandra
We initiated deep X-ray follow up of SN 2014J with the
Chandra X-ray Observatory on 2014 February 3, 20:10:39
UT (δt ∼ 20.4 days) under an approved DDT proposal (PI
Margutti). Data have been reduced with the CIAO software
package (version 4.6) and corresponding calibration files.
Standard ACIS data filtering has been applied. The total
exposure time of our observations is 47ks. The observa-
tions mid-time corresponds to δt = 20.4days since the explo-
sion. No X-ray source is detected at the supernova position
(Fig. 1) with a 3σ upper limit of 2.1 × 10−4
cs−1
in the 0.3-
10 keV energy band, which implies an absorbed flux limit of
Fx < 2.6×10−15
(ergs−1
cm−2
) for an assumed Fν ∝ ν−1
spec-
trum. The count-rate limit is calculated as a 3σ fluctuation
from the local background assuming Poisson statistics as ap-
propriate in the regime of low-count statistics. The presence
of diffuse soft X-ray emission from the host galaxy (Fig. 1,
left panel) prevents us from reaching deeper limits.
The Galactic neutral hydrogen column density in the direc-
tion of SN 2014J is NHMW = 5.1 × 1020
cm−2
(Kalberla et al.
2005). The estimate of the intrinsic hydrogen column (NHint)
is more uncertain. Observations of SN 2014J at optical wave-
lengths point to a large local extinction (see Sec. 3) corre-
sponding to AV = 1.7±0.2mag (Goobar et al. 2014). A more
recent study by Amanullah et al. (2014) find consistent re-
sults around maximum light: AV = 1.9 ± 0.1mag. Assum-
ing a Galactic dust-to-gas ratio, this would imply NHint ∼
4×1021
cm−2
(Predehl & Schmitt 1995; Watson 2011). How-
ever, the low value inferred for the total-to-selective extinc-
tion RV < 2 (Goobar et al. 2014; Amanullah et al. 2014) sug-
gests the presence of smaller dust grains, more similar to the
grain size distribution of the Small Magellanic Cloud (SMC).
For an SMC-like dust-to-gas ratio (Martin et al. 1989), the
inferred hydrogen column is NHint ∼ 7×1021
cm−2
. Gamma-
Ray Burst (GRB) host galaxies sample instead the high end
of the gas-to-dust ratio distribution (Schady et al. 2010).
For a GRB-like environment the observed optical extinc-
tion would imply NHint ∼ 1022
cm−2
. Based on these find-
ings, in the following we calculate our flux limits and re-
sults for a fiducial range of intrinsic hydrogen column den-
sity values: 4 × 1021
cm−2
< NHint < 1022
cm−2
. We adopt
NHint ∼ 7×1021
cm−2
as “central value” in our calculations.4
Based on these values, the unabsorbed flux limit is F3σ
x <
5.0×10−15
ergs−1
cm−2
(NHint = 7×1021
cm−2
, 0.3-10 keV en-
ergy band), with (4.0 < F3σ
x < 6.0)×10−15
ergs−1
cm−2
for the
range of NHint values above. At the distance of 3.5 Mpc,
the corresponding luminosity limit is L3σ
x < 7.2×1036
ergs−1
,
with (5.7 < L3σ
x < 8.7)×1036
ergs−1
.
2.2. Swift-XRT
4 Based on pre-explosion Chandra observations, Nielsen et al. (2014) in-
fer NHint = (8.6 ± 0.4) × 1021 cm−2. However, the actual X-ray absorption
affecting SN 2014J can be either smaller or larger, depending if SN 2014J ex-
ploded in front of some of the material responsible for the intrinsic hydrogen
column in pre-explosion images or if instead SN 2014J illuminated additional
material which was not contributing to the measured NHint.
The Swift (Gehrels et al. 2004) X-Ray Telescope (XRT,
Burrows et al. 2005) started observing SN 2014J on 2014
January 22, 10:13:52 UT (δt ∼ 8 days, PIs Ofek, Brown,
Markwardt, Barthelmy). XRT data have been analyzed us-
ing HEASOFT (v6.15) and corresponding calibration files.
Standard filtering and screening criteria have been applied.
We find no evidence for a point-like X-ray source at the po-
sition of SN 2014J. Using observations acquired at δt < 20
days (total exposure time of 114 ks), the 3σ count-rate limit
is 2.4 × 10−3
cs−1
in the 0.3-10 keV energy range. The un-
absorbed flux limit is F3σ
x < 2.4 × 10−13
ergs−1
cm−2
(NHint =
7×1021
cm−2
), corresponding to L3σ
x < 3.5×1038
ergs−1
. Re-
stricting our analysis to 7 δt 15 days, when X-ray Inverse
Compton emission is expected to peak (Fig. 2), we find a
count-rate limit of 5.4 × 10−3
cs−1
(exposure time of 27 ks,
0.3-10 keV), corresponding to F3σ
x < 5.5 × 10−13
ergs−1
cm−2
with L3σ
x < 8.0×1038
ergs−1
.
3. THE BOLOMETRIC LUMINOSITY OF SN 2014J
The line of sight toward SN 2014J is heavily reddened by
dust in the host galaxy. The Galactic reddening in the direc-
tion of the SN is E(B −V)MW = 0.06mag (Dalcanton et al.
2009). The analysis of the spectra and broad-band photome-
try of SN 2014J by Goobar et al. (2014) indicates a local color
excess E(B − V)host ∼ 1.2mag and a low value of total-to-
selective extinction RV < 2. These results are consistent with
earlier reports by Cox et al. (2014); Patat et al. (2014). In the
remaining of the paper we follow Goobar et al. (2014) and use
E(B−V)host = 1.22±0.05mag with Rhost
V = 1.40±0.15mag.5
The uncertainty on the local extinction parameters is consis-
tently propagated into our final bolometric luminosity (Fig. 2,
lower panel).
To derive the bolometric luminosity of SN 2014J we start
from the UBVRYJHK and iz photometry published by Goo-
bar et al. (2014). We complement this photometric data set
with additional JHK photometry from Venkataraman et al.
(2014); Srivastav et al. (2014); Richardson et al. (2014) and
obtain extinction corrected flux densities applying a Cardelli
et al. (1989) extinction law with the color excess and the
total-to-selective extinction values as above (in addition to the
Galactic correction). A first, pseudo-bolometric light-curve of
SN 2014J is then obtained by integrating the extinction cor-
rected flux densities from the U band (λ ∼ 3650 Å) to the K
band (λ ∼ 2.2µm). From well monitored “normal” Type Ia
SNe like SN 2011fe we estimate that the amount of flux red-
ward the K band is 5% at δt 20days since the explosion.
An UV photometric campaign (PI Brown) has also been
carried out with the Swift (Gehrels et al. 2004) UV Optical
Telescope (UVOT, Roming et al. 2005). However, the large
local extinction makes any extinction correction to the UV
photometry extremely uncertain. For this reason we employ a
different approach. We estimate the time-varying amount of
flux emitted blueward the U band by SN 2014J using the well-
monitored, minimally reddened, normal Type Ia SN 2011fe
as template (Brown et al. 2012; Margutti et al. 2012). At the
time of the Chandra observation (δt = 20.4days) the UV flux
represents (13±5)% of the bolometric flux.
5 The properties of diffuse interstellar bands (DIBs) in the spectra of
SN 2014J would indicate a higher local extinction corresponding to Ahost
V =
2.5±0.1mag (Goobar et al. 2014). A later study by Amanullah et al. (2014)
finds Ahost
V = 1.9 ± 0.1mag. The parameters adopted above imply instead
Ahost
V = 1.7 ± 0.2mag which leads to more conservative limits to the mass-
loss rate of the progenitor system derived in Sec. 4.
3. Lack of X-rays from SN 2014J 3
FIG. 1.— False-color pre-explosion (left panel) and post-explosion (central panel) images of the environment around the Type Ia SN 2014J obtained with the
Chandra X-ray Observatory. Right panel: zoom-in to the SN location. The dashed circle has a radius of 0.9 around the position of SN 2014J (Chandra PSF
at 1.5 keV, 90% containment). No X-ray emission is detected at the position of SN 2014J, enabling deep limits on the mass-loss rate of the stellar progenitor
system. The pre-explosion image combines 237 ks of archival Chandra data (PI Strickland). Our post-explosion observations obtained at δt = 20.4days are
shown in panel (b) (exposure time of 47 ks, PI Margutti). Red, green and blue colors refer to soft (0.3-1.4 keV), medium (1.4-3 keV) and hard (3-10 keV)
photons, respectively.
Figure 2, lower panel, shows the final bolometric light-
curve of SN 2014J. The displayed uncertainty is driven by
the inaccurate knowledge of the local extinction correction.
In this work we use the estimates of Ahost
V and Rhost
V that ap-
peared in the literature so far. It is possible that later esti-
mates will somewhat deviate from the numbers assumed here.
We emphasize that a wrong choice of extinction parameters
would have no impact on our conclusions as long as it does
not lead to an overestimate of the bolometric luminosity of
SN 2014J at ∼ 20 days. The comparison with the UBVRI
light-curves of a sample of Type Ia SNe in Fig. 2 suggests
that we might have instead underestimated the bolometric lu-
minosity of SN 2014J. The study by Amanullah et al. (2014)
finds that SN 2014J is indeed similar to SN 2011fe once cor-
rected for the extinction. If this is true, then our limits on the
density of the explosion local environment should be consid-
ered conservative, thus strengthening our conclusions on the
progenitor system of SN 2014J of Sec. 5. A larger Lbol would
require a smaller environment density in order to avoid detec-
tion of X-rays through Inverse Compton scattering.
4. CONSTRAINTS ON THE PROGENITOR SYSTEM MASS-LOSS
RATE
Deep X-ray observations constrain the density of the ex-
plosion circumstellar environment, previously shaped by the
mass-loss of the progenitor system. For hydrogen-stripped
progenitors in low density environments, at δt 40 days, the
X-ray emission is dominated by Inverse Compton (IC) scat-
tering of photospheric optical photons by relativistic electrons
accelerated by the SN shock (Chevalier & Fransson 2006).
Following the generalized formalism developed in Margutti
et al. (2012), the IC luminosity directly tracks the SN opti-
cal luminosity (LIC ∝ Lbol) and further depends on the density
structure of the SN ejecta ρSN, the structure of the circumstel-
lar medium ρCSM and the details of the electron distribution
responsible for the up-scattering of the optical photons to X-
ray energies. The dynamical evolution of the shockwave is
treated self-consistently. Finally, since LIC ∝ Lbol, any uncer-
tainty on the estimate of the SN distance from the observer
would equally affect LIC and Lbol, and thus has no impact on
the limits we derive on the environment density.
In the following we assume the SN outer density structure
to scale as ρSN ∝ R−n
with n ∼ 10, as found for SNe aris-
ing from compact progenitors (e.g. Matzner & McKee 1999).
Electrons are assumed to be accelerated in a power-law dis-
tribution n(γ) ∝ γ−p
with index p = 3, as supported by ra-
dio observations of SN shocks in Type Ib/c explosions (e.g.
Soderberg et al. 2006). The fraction of post-shock energy den-
sity in relativistic electrons is e = 0.1 (Chevalier & Fransson
2006). The environment density limits calculated below scale
as ( e/0.1)−2
(Margutti et al. 2012, their Appendix A).
We use the bolometric luminosity light-curve derived in
Sec. 3 to constrain the density of the environment around
SN 2014J in the case of (i) a wind-like CSM (ρCSM ∝ R−2
)
and (ii) an ISM-like CSM (ρCSM = const). A star which has
been losing material at constant rate ˙M gives rise to a wind-
like CSM. A “wind medium” is the simplest expectation in the
case of SD progenitor models. DD progenitor systems would
be instead consistent with a “cleaner environment”, and, po-
tentially, with an ISM-like CSM. The final result is shown in
Fig. 2, upper panel.
For a wind-like medium, ρCSM = ˙M/(4πR2
vw), where ˙M
is the progenitor pre-explosion mass-loss rate and vw is the
wind velocity. The X-ray non-detection by Chandra at δt =
20.4days constrains the progenitor mass-loss rate ˙M < 1.2×
10−9
M yr−1
for vw = 100kms−1
. This limit is obtained by
using our fiducial Lbol (thick line in Fig. 2, lower panel) and
4. 4 Margutti et al.
FIG. 2.— Upper panel: Inverse Compton X-ray luminosity expected in the
case of wind (green solid line) and ISM (blue solid line) environments. The
deep X-ray limit obtained with Chandra constrains ˙M < 1.2 × 10−9 M yr−1
(wind) or nCSM < 3.5cm−3 (ISM). The shaded areas mark the range of al-
lowed limits, derived by conservatively accounting for the uncertainty on Lbol
and NHint: ˙M = (0.7−2.5)×10−9 M yr−1 (wind) and nCSM = (1.5−8.0)cm−3
(ISM). Lower panel: optical bolometric luminosity of SN 2014J (thick line)
and associated uncertainty (dotted lines). A sample of UBVRI light-curves of
Type Ia SNe including SNe 1989B, 1991T, 1992A, 1992bc, 1992bo,1994D,
1994ae,1995D, 2011fe (thick solid line), 2012cg, is also shown for compari-
son (from Munari et al. 2013).
L3σ
x < 7.2×1036
ergs−1
(Sec. 2.1). Conservatively accounting
for the uncertainties affecting our estimates of the bolometric
optical luminosity and intrinsic neutral hydrogen absorption
column, the range of allowed limits to the progenitor mass-
loss rate is (0.7−2.5)×10−9
M yr−1
(shaded areas in Fig. 2,
upper panel). In a wind-like scenario ˙M/vw ∝ (1/Lbol)1/0.64
.
For an ISM-like medium we find nCSM < 3.5cm−3
. The range
of allowed limits is (1.5 − 8.0)cm−3
and the particle density
scales as (1/Lbol)0.5
.
Swift-XRT observations have been acquired starting from
δt = 8 days and cover the time interval when IC X-ray emis-
sion peaks. From Figure 2, Lpeak
IC < 2 × 1037
ergs−1
, con-
sistent with the X-ray limit derived from XRT observations
L3σ
x < 8.0×1038
ergs−1
(Sec. 2.2).
5. DISCUSSION
Deep X-ray observations obtained around optical maximum
light of the nearby SN 2014J allowed us to obtain the most
constraining limits on the environment density around a Type
Ia SN explosion. With SN 2011fe (Margutti et al. 2012) and
SN 2014J (this work), we have probed X-ray luminosities
FIG. 3.— Type-I SN explosions in the X-ray phase space, including GRB-
SNe (Margutti et al. 2013), ordinary Type Ib/c SNe (Margutti et al. 2014
and references therein), super-luminous hydrogen poor SNe (SLSNe-I, Levan
et al. 2013) and Type-Ia SNe (Russell & Immler 2012; Schlegel & Petre
1993; Hughes et al. 2007). The emission from SN 2011fe (Margutti et al.
2012) and SN 2014J (stars) is much weaker than any hydrogen-poor core-
collapse SN ever detected in the X-rays, and represent the deepest limit on
the X-ray emission of a Type-I SN to date. Open black symbols mark Type-Ia
SNe with signs of CSM interaction in our sample (i.e. SNe 2002ic, 2005gj,
2006X, 2009ig).
which are a factor ∼ 100 deeper than previously obtained lim-
its (Fig. 3), thus sampling a new territory in the X-ray lumi-
nosity vs. time phase space. However, no X-ray emission
is detected in either case, in sharp contrast with hydrogen-
stripped core-collapse explosions (squares, diamonds and tri-
angles in Fig. 3).
These observations directly constraint the density of mate-
rial in the SN immediate environment, shaped by the progen-
itor system before the terminal explosion. Irrespective of the
assumed circumburst density profile, the deep X-ray limit im-
plies a “clean” environment at distances R 1016
cm from
the explosion center of SN 2014J. We interpret this finding in
the context of different progenitor configurations, both for SD
and DD models.
5.1. SD with quasi-steady mass-loss
WDs around the Chandrasekhar mass MCh accreting at rate
Macc 3 × 10−7
M yr−1
undergo steady hydrogen burning
(e.g. Iben 1982, Nomoto 1982b, Prialnik & Kovetz 1995,
Shen & Bildsten 2007). In this regime the WD accretes and
retains matter. However, the system also loses material to the
environment in three different ways: (i) wind from the donor
star; (ii) non-conservative mass transfer through Roche Lobe
Overflow (RLOF); (iii) optically thick winds from the WD.
In symbiotic systems the wind from the giant compan-
ion star dominates the mass-loss, with typical rates ˙M = 5 ×
10−9
− 5 × 10−6
M yr−1
and wind velocities vw < 100kms−1
(Seaquist & Taylor 1990, Patat et al. 2011, Chen et al.
2011). Our limit on the environment density around SN 2014J
strongly argues against this progenitor scenario (Fig. 4).
5. Lack of X-rays from SN 2014J 5
FIG. 4.— Wind velocity vs. mass-loss phase space. The deep limits we obtain for SN 2014J (colored area) rule out most of the parameter phase space associated
with SD models with steady mass-loss to the environment. The limit obtained from the X-ray observations of SN 2011fe (dashed line, from Margutti et al. 2012)
and the set of limits obtained by Russell & Immler (2012) on a sample of Type Ia SNe (solid black lines) are also shown for comparison. White stars: measured
mass-loss of symbiotic systems in our Galaxy for an assumed vw = 10kms−1 (Seaquist & Taylor 1990).
From the analysis of the complete set of pre-explosion im-
ages (near UV to NIR) at the SN site acquired with the Hub-
ble Space Telescope (HST), Kelly et al. (2014) exclude SD
progenitor systems with a bright red giant donor star. Con-
sistent with these results, the mass-loss limit we derived from
deep X-ray observations of the SN environment firmly and
independently rules out this possibility and extends the con-
clusion to the entire class of red giant secondary stars.
For systems harboring a main sequence, subgiant or helium
star, the dominant source of mass-loss to the surroundings
is through non conservative mass transfer from the donor to
the primary, accreting star. In this scenario the secondary
star fills its Roche lobe and some of the transferred mate-
rial is lost to the environment at the outer Lagrangian point:
˙Mtrans = ˙Macc + ˙Mlost. We use the orbital velocity v ∼ a few
100kms−1
(or lower) as typical velocity of the ejected mate-
rial. Observations of WDs in this regime indicate velocities
up to ∼ 600kms−1
which we use in Fig. 4 (e.g. Deufel et al.
1999). The efficiency of the accretion process ( ˙Macc/ ˙Mtrans)
is poorly constrained. Our X-ray limit implies a very high
efficiency of 99% (light-blue region in Fig. 4) to avoid de-
tectable signs of interaction with the lost material. A similar
value was found for SN 2011fe using deep X-ray and radio
observations (Margutti et al. 2012, Chomiuk et al. 2012). In
this context Panagia et al. (2006) put a less constraining limit
of > 60 − 80% on the efficiency of the same process using
radio observations of a larger sample of 27 SNe Ia.
At high mass transfer rates, optically thick winds develop-
ing at the WD surface are expected to self-regulate the mass
accretion to a critical value ˙Macc ∼ 7 × 10−7
M yr−1
, the ex-
act value depending on the hydrogen mass fraction and WD
mass (Hachisu et al. 1999, Han & Podsiadlowski 2004, Shen
& Bildsten 2007). Our analysis argues against this progenitor
scenario, even in the case of fast outflows with vw ∼ a few
1000kms−1
(dark blue region in Fig. 4).
Finally, thermonuclear burning of hydrogen rich material
on the surface of a WD is expected to generate super-soft
X-ray emission, which should be thus detectable in pre-
explosion images at the SN site. Consistent with our find-
ings above, Nielsen et al. (2014) found no evidence for a
super-soft X-ray source (SSS) at the position of SN 2014J
using deep Chandra X-ray observations spanning the time
range 1 t 14 yr before explosion. These observations al-
lowed Nielsen et al. (2014) to rule out single-degenerate sys-
tems with high effective temperature of the super-soft emis-
sion kTeff > 80eV.
5.2. SD with non-steady mass-loss
Non-steady mass enrichment of the progenitor surround-
ings in the years preceding the SN can create a low-density
cavity around the explosion, which would naturally explain
our X-ray null-detection. The evacuated region around the
progenitor system can either be (i) the consequence of the ces-
sation of mass-loss from the companion star or (ii) the result
of repeated nova shell ejections by the WD.
Recurrent novae. A WD near the Chandrasekhar mass
(M ≥ 1.3M ) accreting at ˙Macc ∼ (0.1−3)×10−7
M yr−1
ex-
periences repeated nova explosions as a result of unsteady
hydrogen burning on its surface (e.g. Iben 1982, Starrfield
et al. 1985, Livio & Truran 1992, Yaron et al. 2005). Shell
ejections associated with the nova outbursts evacuate a region
around the progenitor system by sweeping up the wind from
the companion star. The result is a complex CSM structure,
shaped by the fast nova shells and by the slower wind from
the donor star. This scenario has been invoked to explain the
evidence for interaction in the spectra of some Type Ia SNe
(e.g. SN 2002ic, Wood-Vasey & Sokoloski 2006). The main
outcome of this process is the presence of regions with very
low density, reaching nCSM ∼ 10−3
− 1cm−3
, in the proxim-
ity of the explosion center even in the case of very powerful
6. 6 Margutti et al.
FIG. 5.— CSM density structure around a symbiotic progenitor system
(WD plus red giant star) undergoing repeated nova explosions with recur-
rence time ∆t = 100 yr (from Dimitriadis et al. 2014). Case 1: the SN occurs
just after the last nova explosion. Case 2: the SN explodes 100 yrs after the
last nova shell ejection and the nova cavity has been partially refilled by the
wind of the red giant star with ˙M = 10−6 M yr−1 and vw = 10kms−1. Dashed
vertical lines: radius of the SN forward shock ∼ 20 days after the explosion
(time of our Chandra observations). The CSM densities of the environment
sampled by the SN shock at this time are a factor ∼ 100 smaller than our
limit.
winds from the donor star (Fig. 5).
The immediate SN environment critically depends on the
time of the SN explosion with respect to the time of the last
nova shell ejection, as illustrated by Fig. 5. Figure 5 shows
the results from the simulations by Dimitriadis et al. (2014)
for a symbiotic progenitor system consisting of a WD plus
red giant star losing material with rate ˙M = 10−6
M yr−1
and
wind velocity vw = 10kms−1
. The nova recurrence time scale
in this simulations is ∆t = 100 yrs.
From Fig. 5 it is clear that our observations obtained at δt ∼
20 days do not probe the range of densities associated with
nova cavities.6
However, if the progenitor of SN 2014J ex-
perienced recurrent nova outbursts, our X-ray null-detection
implies that: (i) a nova shell must have been able to clear out
the environment at R ∼ 1016
cm; (ii) the wind from the donor
star has not yet been able to refill this volume by the time of
the SN explosion.
The size of the cavity cleared out by a nova shell depends
on the shell dynamics (e.g. Moore & Bildsten 2012). For
typical shell ejection velocities vsh = 1000 − 4000kms−1
and
mass Msh = 10−7
−10−5
M (Yaron et al. 2005) expanding into
a medium enriched by the secondary star mass-loss with rate
˙M = 10−7
−10−6
M y−1
, the shell rapidly evolves from free ex-
pansion to the Sedov-Taylor phase on a time-scale of tST ∼ a
few days. It then transitions to the snowplow phase at tSP ∼ a
few months. Adopting vsh = 4000kms−1
, tST = 2 days, tSP = 2
months as typical parameters as indicated by observations of
the recurrent nova RS Oph (e.g. Bode & Kopal 1987, Mason
et al. 1987, Sokoloski et al. 2006), a nova shell would reach
R ∼ 1016
cm on a time scale of ∼ 40 yrs. For a wind envi-
ronment R ∝ t2/3
during the Sedov-Taylor phase and R ∝ t1/2
during the snowplow phase. The slower wind from the donor
star would need ∆trefill ∼ 300 yrs to refill this region with new
6 However, according to Dimitriadis et al. (2014), their Fig. 12, we should
have been able to detect X-ray emission at the level of Lx ≥ 5 × 1037 ergs−1
at δt ∼ 20 days if the X-rays are of thermal origin. Such emission is clearly
ruled out by our observations.
material (for vw = 10kms−1
).
These results indicate that if the recurrent nova scenario
applies to SN 2014J, then (i) at least one nova shell has been
ejected at t ≥ 40 yrs before the SN; (ii) the recurrence time
scale of nova outbursts is shorter than 300 yrs (consistent
with the time scales observed in recurrent novae, the short-
est known time between outbursts being ∼ 1 yr at the time of
writing, Tang et al. 2014). To this respect it is worth mention-
ing that a complementary search for nova outbursts in archival
optical images revealed no evidence for nova explosions at the
location of SN 2014J in the ∼ 1500 days before the SN (Goo-
bar et al. 2014). No evidence for interaction has been found
for SN 2014J at δt ≤ 20 days since the explosion, either in
the form of light-curve re-brightenings, Hα emission or time-
variable Na D features (Goobar et al. 2014; Zheng et al. 2014;
Tsvetkov et al. 2014), consistent with the expansion in a very
clean environment. The same conclusion is supported by the
deep limits on the radio synchrotron emission by Chomiuk
et al. (2014) and Chandler & Marvil (2014).
Cessation of mass-loss. Our observations at δt ∼ 20 days
cannot exclude the presence of material in the environment
at larger distances R 1016
cm and are thus consistent with
any scenario that predicts cessation of mass loss from the pro-
genitor system at t ≥ 300 × (vw/10kms−1
)−1
yrs before the
terminal explosion ("delayed explosion models" in Fig. 4).
This condition is naturally satisfied by (i) spin-up/spin-down
models (Di Stefano et al. 2011; Justham 2011) and (ii) core-
degenerate scenarios for Type Ia SNe (where the WD merges
with the core of an AGB -Asymptotic Giant Branch- star,
Ilkov & Soker 2012).
In both cases rapid rotation might stabilize the WD against
explosion, allowing the WD to grow above MCh. The actual
delay time τ between completion of mass transfer and explo-
sion is uncertain and depends on the physical mechanism that
regulates the WD spin-down (i.e. reduced accretion, ceased
mass transfer, angular momentum transfer, magnetic break-
ing, gravitational waves). A wide range of values seems to
be allowed by theory (τ 105
yrs to τ > 109
yrs, e.g. Lind-
blom et al. 1999, Yoon & Langer 2005, Ilkov & Soker 2012,
Hachisu et al. 2012). Here it is worth noting that τ ≥ 105
yrs is enough for the circumbinary material to become diffuse
and reach ISM-like density values at the explosion site, con-
sistent with our findings. Additionally, for τ 108
−109
yrs,
even if the donors started the mass-loss as giant, sub-giant or
main sequence stars, by the time of the explosion they have
exhausted most of their envelopes, their remaining envelopes
have shrunk inside their Roche lobes and/or they are likely to
have already evolved into compact objects (e.g. He or C/O
WDs) or low-mass stars (e.g. Di Stefano et al. 2011, Justham
2011, Hachisu et al. 2012). All these effects would suppress
any prominent signature of the mass-donor companion both
before (i.e. in pre-explosion images) and after the explosion
(i.e. anything that originates from the interaction of the SN
shock with the medium), naturally accounting for our null-
detections.
5.3. WD-WD progenitors
In double-degenerate models the merger of two WDs leads
to the final explosion. The general expectation is that of a
“clean” environment at R 1013
−1014
cm with ISM-like den-
7. Lack of X-rays from SN 2014J 7
sity.7
No stellar progenitor is expected to be detectable at the
distance of SN 2014J in near UV to NIR pre-explosion im-
ages. Additionally, since the WDs were unlikely to burn hy-
drogen just prior to explosion, no X-ray source is expected to
be found in pre-explosion images either. Our deep X-ray non-
detection is consistent with this scenario, but can hardly be
considered a confirmation of this progenitor channel. We also
note that our results are consistent with the predictions of the
core-degenerate (CD) scenario, where the actual merger in-
volves a WD and the core of an asymptotic giant branch star,
as suggested in the case of SN 2011fe (Soker et al. 2014).
WD-WD mergers are however expected to enrich the ISM
in a number of ways including (i) tidal tail ejections (Raskin
& Kasen 2013), (ii) mass outflows during the rapid accretion
phase before the merger (Guillochon et al. 2010, Dan et al.
2011), (iii) winds emanating from the disk during the vis-
cous evolution (Ji et al. 2013), (iv) shell ejections (Shen et al.
2013. See also Soker et al. 2013). Each of these mechanisms
predicts the presence of relevant mass at different distances
from the explosion center. Below we discuss the predictions
of these scenarios at R ∼ 1016
cm which is relevant for the
Chandra null detection of SN 2014J.
Tidal tail ejection. Some 10−4
− 10−2
M of material is ex-
pected to be tidally stripped and ejected with typical veloc-
ity vej ∼ 2000kms−1
just prior to the WD-WD coalescence
(Raskin & Kasen 2013). The resulting structure of the CSM
and the distance Rej of the over-density region created by the
mass ejection from the explosion center critically depend on
the delay time between the tidal tail ejection and the final ex-
plosion ∆tej. In particular, the ejected material would require
∆tej ∼ 108
s to reach the distance of interest Rej ∼ 1016
cm.8
Raskin & Kasen 2013 calculate that the tidal tail density at
this distance would correspond to an effective mass-loss rate
˙M ∼ 10−2
− 10−5
M yr−1
which is ruled out by our observa-
tions. Our results thus argue against WD-WD mergers with
delay times of the order of 1-10 yrs, but allow for short delay
times ∆tej < 106
s (including systems that detonate on the dy-
namical time scale ∆tej ∼ 102
− 103
s or on the viscous time
scale of the remnant disk ∆tej ∼ 104
− 108
s). Long lag times
∆tej 108
s are also consistent with our findings, since the
interacting material would be located at larger distances.
Mass outflows during rapid accretion. Guillochon et al.
(2010) and Dan et al. (2011) suggested that a phase of mass
transfer and rapid accretion (with accretion rates reaching
10−5
−10−3
M s−1
) might precede the actual WD-WD merger.
As for SD systems, mass can be lost at the Lagrangian point,
thus shaping the environment that the SN shock will probe
later on. According to the simulations by Dan et al. (2011),
by the time of the merger the mass of the unbound material is
Mej ∼ 10−2
−10−3
M and could in principle produce observ-
able signatures as soon as the SN shock and ejecta expand
and interact with this material. The dynamics of the ejected
material depends on vej, Mej and nISM. The location of the
ejected material Rej at the time of the SN explosion critically
depends on ∆tej. Both ∆tej and vej are at the moment poorly
7 Recent DD studies pointed out the possible presence of a region of en-
hanced density located at R ∼ 1013 − 1014 cm (e.g. Fryer et al. 2010, Shen
et al. 2012, Raskin & Kasen 2013). Its physical origin has to be connected ei-
ther to the WD-WD merger and/or to the outcome of the subsequent evolution
of the system.
8 Note that for typical ISM densities nISM ∼ 1cm−3, the ejected material
is in free expansion for ∼ 200 yrs before entering the Sedov-Taylor phase.
constrained. For vej ∼a few 1000kms−1
(i.e. comparable to
the escape velocity), our deep density limit at R ∼ 1016
cm im-
plies that the system did not eject substantial material in the
2-3 years before the SN explosion.
Disk winds. WD-WD mergers that fail to promptly deto-
nate have been recently suggested to produce a rapidly rotat-
ing, magnetized WD merger surrounded by a hot thick accre-
tion disk before producing a Type Ia SN (Ji et al. 2013). A
fraction of the disk mass is lost through magnetically driven
winds. Ji et al. (2013) calculate that for near-equal mass WD,
Mej ∼ 10−3
M is gravitationally unbound and ejected with
vej ∼ 2600kms−1
. As for the other scenarios, a critical param-
eter is the interval of time between the mass ejection and the
supernova explosion ∆tej (assuming that a supernova occurs).
The low density of SN 2014J at R ∼ 1016
cm suggests ∆tej >
a few yrs.
Shell ejection. In the case of He+C/O WD progenitors in
the context of the “double detonation” model (Livne 1990),
Shen et al. (2013) have recently proposed that hydrogen-rich
material can be ejected by the binary system in multiple ejec-
tion episodes hundreds to thousands of years prior to the
merger (see their Fig. 3). In their simulations Shen et al.
(2013) find that a total of Mej = (3−6)×10−5
M of material
can be transferred to the environment and it is ejected with
initial velocity vej ∼ 1500kms−1
(i.e. comparable with the He
WD circular velocity). In close analogy to nova shells, the
ejected material interacts with the local ISM and shapes the
local environment of the explosion (Shen et al. 2013, their
Fig. 4). Both the delay time between the onset of the mass-
transfer and the disruption of the He WD and the time of the
last ejection critically depend on the evolutionary history of
the He WD, with the “older” He WD in the simulations of
Shen et al. 2013 giving origin to mass ejections ∼ 200 yrs be-
fore the terminal explosion. Our finding of a very low density
environment at R ∼ 1016
cm constrains the most recent mass
ejection in SN 2014J (if any) to have happened at t > 3 yrs
before the explosion.
6. CONCLUSIONS
Type Ia SNe remain among the class of SNe that still lacks
both an X-ray and radio counterpart identification. Our Chan-
dra monitoring campaigns of the two most nearby SNe Ia
in the last 30 years, SN 2011fe (Margutti et al. 2012), and
SN 2014J (this work), allowed us to sample a new region of
the Lx vs. time parameter space (Lx < 7 × 1036
ergs−1
, Fig.
3), and offered us the opportunity to probe the environment
density down to the unprecedented level of a few particles per
cm3
at R 1016
cm.
Our major findings can be summarized as follows:
• The deep X-ray null detection of SN 2014J at ∼ 20
days (Lx < 7 × 1036
ergs−1
) implies a low density en-
vironment with nCSM < 3cm−3
at R ∼ 1016
cm from the
center of the explosion (ISM medium). For a wind-
like density profile, the luminosity above translates into
a pre-explosion mass-loss rate ˙M < 10−9
M yr−1
for
wind velocity vw = 100kms−1
. By contrast to limits
derived from radio synchrotron emission, our results
are independent of assumptions about the poorly con-
strained post-shock energy density in magnetic fields
(e.g. Chomiuk et al. 2012, Horesh et al. 2012 for
SN 2011fe).
8. 8 Margutti et al.
• These results rule out with high confidence the major-
ity of the parameter space populated by SD models with
steady mass-loss until the terminal explosion (Fig. 4),
and in particular symbiotic systems with a giant com-
panion.
• If the progenitor system of SN 2014J is SD and har-
bors a main sequence or subgiant mass-donor star un-
dergoing Roche lobe overflow, our results imply a
high efficiency of the accretion process onto the WD
˙Macc/ ˙Mtrans 99%.
• In the allowed portion of the progenitor parameter
space (Fig. 4) we find WD-WD scenarios (both DD
with a pair of C/O WDs and He+C/O WDs of the dou-
ble detonation model), SD systems undergoing unsta-
ble hydrogen burning, and SD or DD models where
the terminal explosion is delayed with respect to the
completion of the mass loss. A delay time as short as
∼ 300×(v/10kms−1
)−1
yrs would be enough to explain
our X-ray null-detection. Alternatively, SD progenitors
burning hydrogen unsteadily experience repeated nova
shell ejections. If SN 2014J originates from this class
of progenitors, our results suggest that, for typical nova-
shell and SN environment parameters, (i) at least one
nova shell has been ejected at t ≥ 40 yrs before the SN,
(ii) the recurrence time of shell ejection by our system
is < 300 yrs.
This discussion emphasizes that a single deep X-ray
observation of a nearby Type Ia SN has strong discriminating
power in the case of progenitors with steady mass-loss until
the terminal explosion. However, a change in the observation
strategy, with multiple deep observations obtained in the first
∼ 100 days since the explosion is needed to better constrain
scenarios with sporadic mass-loss episodes just before the
terminal explosion. We advocate for such observations to
be obtained for the next Type Ia SN discovered in the local
Universe (d < 10Mpc). Late-time (t 100 days) deep
X-ray observations will be able to sample the more distant
environment: for example, recent analysis of the Type Ia SN
remnant Kepler suggests that CSM cavities may reach out
to R ∼ 1017
cm (Patnaude et al. 2012). This effort must be
paralleled by realistic theoretical predictions of the environ-
ment density structure around the explosion, possibly shaped
by repeated mass ejections from the progenitor system for a
wide range of progenitor/environment parameters.
We thank H. Tananbaum and the entire Chandra team
for making the X-ray observations possible. R. M. thanks
Lorenzo Sironi, Cristiano Guidorzi and James Guillochon for
many instructive discussions and Georgios Dimitriadis for
clarifications about his nova ejection simulations. Support
for this work was provided by the David and Lucile Packard
Foundation Fellowship for Science and Engineering awarded
to A. M. S. R. K. acknowledges support from the National
Science Foundation through grant AST12-11196.
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