Detection of magnetic_fields_in_both_b_type_components_of_epsilon_lupi_system...Sérgio Sacani
Uma equipe de astrônomos detectou um chamado campo magnético fóssil em ambos os componentes de um sistema estelar binário, chamado de Epsilon Lupi.
Epsilon Lupi, também conhecida como HD 136504, é uma estrela binária brilhante, localizada na constelação do hemisfério sul de Lupus.
O par de estrelas está localizado a aproximadamente 500 anos-luz de distância da Terra, e cada estrela tem entre 7 e 8 vezes a massa do Sol, e combinadas, elas têm cerca de 6000 vezes a luminosidade do Sol.
Os astrônomos sabem de muito tempo que a Epsilon Lupi é um sistema binário, mas não tinham ideia de que as duas estrelas pudessem possuir campos magnéticos.
“A origem do magnetismo entre estrelas massivas é um mistério e essa descoberta pode ajudar a trazer uma luz numa questão de por que essas estrelas possuem campos magnéticos”, disse Matt Shultz da Universidade de Queen no Canadá, e o principal autor do artigo aceito para publicação no Monthly Notices of the Royal Astronomical Society e que descreve a descoberta.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
Detection of magnetic_fields_in_both_b_type_components_of_epsilon_lupi_system...Sérgio Sacani
Uma equipe de astrônomos detectou um chamado campo magnético fóssil em ambos os componentes de um sistema estelar binário, chamado de Epsilon Lupi.
Epsilon Lupi, também conhecida como HD 136504, é uma estrela binária brilhante, localizada na constelação do hemisfério sul de Lupus.
O par de estrelas está localizado a aproximadamente 500 anos-luz de distância da Terra, e cada estrela tem entre 7 e 8 vezes a massa do Sol, e combinadas, elas têm cerca de 6000 vezes a luminosidade do Sol.
Os astrônomos sabem de muito tempo que a Epsilon Lupi é um sistema binário, mas não tinham ideia de que as duas estrelas pudessem possuir campos magnéticos.
“A origem do magnetismo entre estrelas massivas é um mistério e essa descoberta pode ajudar a trazer uma luz numa questão de por que essas estrelas possuem campos magnéticos”, disse Matt Shultz da Universidade de Queen no Canadá, e o principal autor do artigo aceito para publicação no Monthly Notices of the Royal Astronomical Society e que descreve a descoberta.
Science with small telescopes - exoplanetsguest8aa6ebb
The search for extrasolar planets has become one of the most attractive problems in modern astrophysics. The biggest observatories in the world are involved in this task as well as little amateur instruments. There is also a huge variety of astronomical methods used for their investigation. Here I present the projects for searching for exoplanets by transit method and our observations of the planet WASP-2b. We observed a transit on 3/4 August 2008 with a 354 mm Schmidt-Cassegrain Celestron telescope and CCD SBIG STL 11000M camera. By precise photometry made using MaximDL software we obtained the light curve of the star system. Decrease of brightness by 0.02m is detected. Analyzing our data we estimate the radius of the planet and inclination of its orbit. Our results are in good correlation with the published information in literature.
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.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
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.
Merging galaxy clusters leave long-lasting signatures on the baryonic and non-baryonic cluster constituents,
including shock fronts, cold fronts, X-ray substructure, radio halos, and offsets between the dark matter (DM) and
the gas components. Using observations from Chandra, the Jansky Very Large Array, the Giant Metrewave Radio
Telescope, and the Hubble Space Telescope, we present a multiwavelength analysis of the merging Frontier Fields
cluster MACS J0416.1-2403 (z = 0.396), which consists of NE and SW subclusters whose cores are separated on
the sky by ∼250 kpc. We find that the NE subcluster has a compact core and hosts an X-ray cavity, yet it is not a
cool core. Approximately 450 kpc south–southwest of the SW subcluster, we detect a density discontinuity that
corresponds to a compression factor of ∼1.5. The discontinuity was most likely caused by the interaction of the
SW subcluster with a less massive structure detected in the lensing maps SW of the subclusterʼs center. For both
the NE and the SW subclusters, the DM and the gas components are well-aligned, suggesting that MACS J0416.1-
2403 is a pre-merging system. The cluster also hosts a radio halo, which is unusual for a pre-merging system. The
halo has a 1.4 GHz power of (1.3 ± 0.3) × 1024WHz−1, which is somewhat lower than expected based on the
X-ray luminosity of the cluster if the spectrum of the halo is not ultra-steep. We suggest that we are either
witnessing the birth of a radio halo, or have discovered a rare ultra-steep spectrum halo.
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.
Matter ejections behind the highs and lows of the transitional millisecond pu...Sérgio Sacani
Transitional millisecond pulsars are an emerging class of sources linking low-mass X-ray binaries to millisecond radio pulsars in
binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active
state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray
to optical pulsations are observed only during the high mode. Knowledge of the root reason for this puzzling behaviour remains
elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar
prototype, PSR J1023+0038, covering from radio to X-rays. The campaign was carried out over two nights in June 2021, and involved
12 different telescopes and instruments including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA and FAST.
By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by
changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on
top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with A
Similar to Strong evolution xray_absorption_sn_2010jl (20)
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.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
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Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
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linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
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Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
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GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
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Search and Society: Reimagining Information Access for Radical Futures
Strong evolution xray_absorption_sn_2010jl
1. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 doi:10.1088/2041-8205/750/1/L2
C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
STRONG EVOLUTION OF X-RAY ABSORPTION IN THE TYPE IIn SUPERNOVA SN 2010jl
Poonam Chandra1 , Roger A. Chevalier2 , Christopher M. Irwin2 , Nikolai Chugai3 ,
Claes Fransson4 , and Alicia M. Soderberg5
1 Department of Physics, Royal Military College of Canada, Kingston, ON, K7K 7B4, Canada; Poonam.Chandra@rmc.ca
2 Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325, USA
3 Institute of Astronomy of Russian Academy of Sciences, Pyatnitskaya St. 48, 109017 Moscow, Russia
4 Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden
5 Smithsonian Astrophysical Observatory, 60 Garden St., MS-20, Cambridge, MA 02138, USA
Received 2012 February 7; accepted 2012 March 23; published 2012 April 4
ABSTRACT
We report two epochs of Chandra-ACIS X-ray imaging spectroscopy of the nearby bright Type IIn supernova SN
2010jl, taken around two months and then a year after the explosion. The majority of the X-ray emission in both
spectra is characterized by a high temperature ( 10 keV) and is likely to be from the forward shocked region
resulting from circumstellar interaction. The absorption column density in the first spectrum is high (∼1024 cm−2 ),
more than three orders of magnitude higher than the Galactic absorption column, and we attribute it to absorption
by circumstellar matter. In the second epoch observation, the column density has decreased by a factor of three,
as expected for shock propagation in the circumstellar medium. The unabsorbed 0.2–10 keV luminosity at both
epochs is ∼7 × 1041 erg s−1 . The 6.4 keV Fe line clearly present in the first spectrum is not detected in the second
spectrum. The strength of the fluorescent line is roughly that expected for the column density of circumstellar gas,
provided the Fe is not highly ionized. There is also evidence for an absorbed power-law component in both spectra,
which we attribute to a background ultraluminous X-ray source.
Key words: circumstellar matter – hydrodynamics – supernovae: general – supernovae: individual (SN 2010jl) –
X-rays: general
Online-only material: color figures
1. INTRODUCTION reddening, indicating that the dust does not have a spherically
symmetric distribution about the SN (Andrews et al. 2011). The
Supernova (SN) 2010jl was discovered on 2010 November Swift onboard X-ray Telescope (XRT) detected X-rays from
3.5 (UT) at a magnitude of 13.5 (Newton & Puckett 2010), and SN 2010jl on 2010 November 5.0–5.8 (Immler et al. 2010).
brightened to magnitude 12.9 over the next day, showing that Assuming a temperature of 10 keV and a Galactic absorption
it was discovered at an early phase. Pre-discovery observations column of NH = 3.0×1020 cm−2 , Immler et al. (2010) obtained
indicate an explosion date in early 2010 October (Stoll et al. an unabsorbed X-ray luminosity of (3.6 ± 0.5) × 1040 erg s−1
2011). Spectra on 2010 November 5 show that it is a Type IIn in the 0.2–10 keV band.
event (Benetti et al. 2010). The apparent magnitude is the After the detection of SN 2010jl with the Swift-XRT, we
brightest for a Type IIn SN since SN 1998S. SN 2010jl is triggered Chandra observations of the SN at two epochs, in
associated with the galaxy UGC 5189A at a distance of 50 Mpc 2010 December and 2011 October, and we present the results
(z = 0.011), implying that SN 2010jl reached MV ∼ −20 here (Section 2). We discuss the significant changes in the two
(Stoll et al. 2011) and placing it among the more luminous Chandra observations taken 10 months apart in Section 3.
Type IIn events (Kiewe et al. 2012). Hubble Space Telescope
(HST) images of the site of the SN taken a decade before the SN 2. OBSERVATIONS AND ANALYSIS
indicate that, unless there is a chance coincidence of a bright star 2.1. Observations
with the SN site, the progenitor star had an initial mass 30 M
(Smith et al. 2011). Optical spectra give evidence for a dense The Swift detection of SN 2010jl allowed us to trigger our
circumstellar medium (CSM) expanding around the progenitor approved Chandra Cycle 11 program in 2010 December. We
star with speeds of 40–120 km s−1 (Smith et al. 2011). Stoll again observed SN 2010jl in 2011 October under Cycle 13
et al. (2011) found that the host galaxy is of low metallicity, of Chandra. The first observation (Figure 1) took place under
supporting the emerging trend that luminous SNe occur in low- proposal 11500430 starting 2010 December 7 at 04:22:53 hr
metallicity environments. They determine the metallicity Z of (UT) for an exposure of 19.05 ks and then on 2010 December 8 at
the SN region to be 0.3 Z . 00:50:20 hr (UT) for a 21.05 ks exposure. The observations were
Spitzer observations showed a significant infrared (IR) excess taken with ACIS-S without grating in a VFAINT mode. A total
in SN 2010jl, indicating either new dust formation or the heating of 39.58 ks exposure time was used in the data analysis and 468
of circumstellar dust in an IR echo (Andrews et al. 2011). counts were obtained with a count rate of (1.13 ± 0.05) × 10−2
Andrews et al. (2011) attributed the IR excess to pre-existing counts s−1 . The second set of observations (Figure 2) took
dust and inferred a massive CSM around SN 2010jl. Smith place under our proposal 13500593 starting on 2011 October
et al. (2012) found signatures of new dust formation in the post- 17 at 20:25:09 hr (UT) for an exposure of 41.04 ks. The
shock shell of SN 2010jl from their multi-epoch spectra. While observations were again taken with ACIS-S in the VFAINT
a significant IR excess is present, the SN does not show large mode with grating NONE. From a total of 40.51 ks usable
1
2. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 Chandra et al.
5×10−3
2×10−3
normalized counts s−1 keV−1 10−3
5×10−4
2×10−4
10−4
sign(data−model) × ∆ χ2
2
0
0.2 0.5 1 2 5 10
Energy (keV)
Figure 1. Best-fit Chandra spectrum of SN 2010jl taken in 2010 December. The spectrum is best fit with a high-T, high-NH thermal component, a Gaussian at 6.4 keV,
and a power law with photon index Γ = 1.76.
(A color version of this figure is available in the online journal.)
0.01
normalized counts s−1 keV−1
10−3
sign(data−model) × ∆ χ2
0
−5
0.2 0.5 1 2 5 10
Energy (keV)
Figure 2. Best-fit Chandra spectrum of SN 2010jl taken in 2011 October. The plot is for the model when the column densities of both temperature components (green
dashed line and the blue dashed line) are allowed to vary independently in the fit.
(A color version of this figure is available in the online journal.)
exposure time, we obtained 1342 total counts, i.e., a count rate of 2.2. Spectral Analysis
(3.29 ± 0.09) × 10−2 counts s−1 . We extracted the spectra using
As can be seen in Figures 1 and 2, the normalized count rate
CIAO software6 and used HEAsoft7 to carry out the spectral
is higher in the 2011 October spectra. This does not necessarily
analysis.
indicate higher intrinsic emission from the SN at the later
6 http://asc.harvard.edu/ciao/ time, because the count rates are absorbed count rates and
7 http://heasarc.gsfc.nasa.gov/docs/software/lheasoft/ the unabsorbed emission depends on the intervening column
2
3. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 Chandra et al.
Fe lines
Normalized Counts s−1 keV−1
0.007
Dec 2010 Oct 2011
0.006
0.005
0.004
0.003
0.002
0.001
5.5 6.0 6.5 7.0 7.5 5.5 6.0 6.5 7.0 7.5
Energy(keV) Energy(keV)
Figure 3. Comparison of the 2010 December and 2011 October spectra around the Fe 6.4 keV line energy. The line is clearly visible at the early time, but not at the
later time.
Table 1
Spectral Model Fits to the SN 2010jl Spectra
Spectrum Model χ 2 /ν NH Parameter Abs. Flux Unabs. Flux
2010 Dec Mekal 0.84(23) 9.70+1.60 × 1023
−1.61 kT = 79.9+···
−68.03 6.55 × 10−13 2.44 × 10−12
+ Gaussian ··· ··· E = 6.32+0.06
−0.06 2.43 × 10−14 4.25 × 10−14
+ PowerLaw ··· 3.0 × 1020 (fixed) Γ= 1.68+0.66
−0.72 1.21 × 10−14 1.29 × 10−14
Mekal 0.87(24) 10.59+1.77
−1.28 × 1023 kT = 8.0 (fixed) 5.57 × 10−13 3.23 × 10−12
+ Gaussian ··· ··· E = 6.32+0.06
−0.06 3.02 × 10−14 5.56 × 10−14
+ PowerLaw ··· 3.0 × 1020 (fixed) Γ = 1.63+0.70
−0.64 1.18 × 10−14 1.24 × 10−14
2011 Oct Mekal 0.92(75) 2.67+3.47 × 1023
−0.48 kT = 79.9+···
−68.55 1.04 × 10−12 2.13 × 10−12
+ Mekal ··· 8.38+0.52 × 1022
−0.43 kT = 1.05+0.95
−0.44 3.76 × 10−14 4.94 × 10−13
+ PowerLaw ··· 3.0 × 1020 (fixed) Γ = 1.54+0.73
−0.71 2.37 × 10−14 2.42 × 10−14
Mekal 0.99(78) 3.51+2.52 × 1023
−1.14 kT = 12 (fixed) 9.49 × 10−13 2.62 × 10−12
+ Mekal ··· 9.06+3.95 × 1022
−2.42 kT = 1.15+1.41
−0.53 5.34 × 10−14 5.87 × 10−13
+ PowerLaw ··· 3.0 × 1020 (fixed) Γ = 1.76+0.81
−0.84 1.97 × 10−14 2.15 × 10−14
Notes. Here, NH is in cm−2 , E is in keV, and the fluxes are in erg cm−2 s−1 . The fluxes are given in the 0.2–10.0 keV energy range. The absorbed and unabsorbed
fluxes are for that particular component in the model. The errors in the fluxes are 20%–30%.
density, which may change. In the 5.5–7.5 keV range, the is a lower limit on the temperature of the main X-ray emission
fluorescent 6.4 keV Fe line is present in the first spectrum component of the SN. For the lower temperature component
but not the second (Figure 3). Here we carry out a detailed in the 0.2–2 keV range, we fix the absorption column to the
spectral analysis of both spectra and determine the significance Galactic value of 3.0 × 1020 cm−2 since the absorption column
of various emission components along with the Fe 6.4 keV line. for this component is very poorly constrained. This component
is best fit with a temperature of ∼2 keV or a power law with
2.2.1. 2010 December Spectrum Γ = 1.76.
Figure 1 shows the best fit to the Chandra spectrum taken
For the 2010 December spectrum, we first fit the high- between 2010 December 07.18 UT and 08.03 UT, and the
temperature component in the 2–10 keV energy range, where best fits are tabulated in Table 1. Our complete model is
most of the emission in the Chandra energy band lies. We fit the the Absorption×Powerlaw + Absorption×(Mekal + Gaussian).
spectrum in this range with an absorbed Mekal model (Mewe 97.9% of the total unabsorbed flux in the Chandra band is
et al. 1985; Liedahl et al. 1995) with metallicity Z = 0.3 Z carried by the high-temperature component. The Fe 6.4 keV
(Stoll et al. 2011). The preferred Mekal temperature always line carries 1.7% of the total flux while the low-NH component
hits the upper bound of the temperature allowed in the Mekal only has 0.4% of the total flux. The rest energy of the Fe line
model, i.e., 79.9 keV. The column density is also very high, with is 6.39 ± 0.06 keV, which is consistent with the Kα line. The
NH ≈ 1024 cm−2 . Since the temperature in the best-fit models equivalent width of the line is EWFe = 0.2 ± 0.1 keV.
seems high, we checked for the possibility of a non-thermal
X-ray emission and fit a power-law model. The column density 2.2.2. 2011 October Spectrum
in this fit is consistent with that of the Mekal model; however, the
photon index is too small to be physically plausible (Γ = 0.33), The Chandra spectrum taken between 2011 October
and we disfavor the non-thermal model. 17.85–18.33 UT is different from the first epoch spectrum. We
When we plot the confidence contours of NH versus kT , the first fit the high-temperature component between 2 and 10 keV.
column density in our fits is well constrained, but the upper The temperature in this case also reaches the Mekal model
bound of the temperature is not constrained (Figure 4). We upper limit of 79.9 keV. To consider the possibility of non-
established a lower bound on the temperature by assuming a thermal emission, we fit a power law to the spectrum. However,
value and finding the goodness of fit; T = 8 keV gives a good the power-law fit to this component yields a photon index of
fit with acceptable χ 2 value, but not lower values. Thus, 8 keV Γ = 0.45, which is implausible.
3
4. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 Chandra et al.
+
80
60
kT(keV)
40
20
60 80 100 120 140
NH (1022 cm−2)
Figure 4. Plot shows 68% (black), 90% (red), and 99% (green) confidence contours for the NH vs. kT confidence contours plot for the 2010 December spectrum. The
column density is well constrained while the temperature is unconstrained on the high side.
(A color version of this figure is available in the online journal.)
In this spectrum, the column density has decreased by a showing that a hot component is present. The column den-
factor of three; the best-fit column density for Z = 0.3 Z sities of the main X-ray emission component (high-NH com-
is ∼3 × 1023 cm−2 . The Fe 6.4 keV line is not present, but the ponent) are high at both epochs. The column densities at the
low-temperature component is there. Because of few data points first and second epochs are ∼1024 cm−2 and 3 × 1023 cm−2
and a large uncertainty in the column density in this component, (for a metallicity of Z ≈ 0.3 Z ), respectively. These are
we again fix the column density to the Galactic value. When 3000 times and 1000 times higher than the Galactic column
we fit the low-temperature component with a thermal plasma density (3 × 1020 cm−2 ). The high value and variability of NH
or a power-law model, it fits with a temperature of ∼1–2 keV point to an origin in the CSM. The excess column density to
or a power law of ∼1.7. However, another component is still the X-ray emission is not accompanied by high extinction to the
required by the data. When we try to fit this component using the SN, showing that the column is probably due to mass loss near
same column density as that of the main emission component, the forward shock wave where any dust has been evaporated.
we find T = 0.11 keV and a very high unabsorbed luminosity This is the first time that external circumstellar X-ray absorption
∼1045 erg s−1 , which is implausible. Thus, we try to fit this has been clearly observed in an SN.
component with an independently varying column density. Assuming 2010 October 10 as the date of explosion (Andrews
The column density associated with this component is around et al. 2011; Patat et al. 2011), the epochs of the two Chandra
1/4 that of the high-NH component column density. This gives observations are 59 and 373 days, respectively. The 0.2–10 keV
a reasonable and physically plausible component and indicates absorbed flux at the second epoch (1.1 × 10−12 erg cm−2 s−1 )
that the flux is this component is 15%–20% of the total emission. is higher than that at the first epoch (6.5 × 10−13 erg cm−2 s−1 ),
Thus, in this spectrum, we have three components: a high-NH but this is due to the lower absorption column density at the
high-T component, a high-NH low-T component, and a low-NH second epoch. The actual unabsorbed emission from the SN is
component. constant within 20%–30%. At the two epochs, the unabsorbed
Although the preferred temperature again reaches the up- luminosity in the 0.2–10 keV band is ∼7 × 1041 erg s−1 , placing
per bound allowed by the Mekal model, the error determi- SN 2010jl among the most luminous X-ray SNe yet observed.
nation shows that there is no upper bound and the lower Table 1 of Immler (2007) shows that the only other SNe
bound to the temperature is 12 keV. Our final model thus is with comparable luminosities are Type IIn events or gamma-
Absorption×Power law + Absorption×Mekal+Absorption× ray burst associated SNe at early times. The luminosity of
Mekal. Figure 2 shows the best fit to the Chandra 2011 3.6 ± 0.5 × 1040 erg s−1 found by Swift on 2010 November
October spectrum. Table 1 lists the models and best-fit param- 5 (Immler et al. 2010) is revised to a value close to our
eters. In this case, 81.1% of the unabsorbed flux is carried by Chandra result if NH ∼ 1024 cm−2 is assumed. In the thermal
the high column density component, 18.2% by the lower-NH interpretation, the shock velocity can be deduced as vsh =
component, and 0.7% is carried by the power-law component. [16 kT /(3µ)]1/2 = 7700(kT /80 keV)1/2 km s−1 , where k is
Boltzmann’s constant and µ is the mean particle weight. A
3. RESULTS AND INTERPRETATION lower limit of 10 keV for the temperature puts a lower limit of
the 2700 km s−1 on the shock speed.
Here we highlight the main differences between the 2010 In comparing the observed luminosity to a thermal emission
December and 2011 October spectra and discuss the best-fit model to find the physical parameters, we note that our measure-
models and their implications. The lower limits on the temper- ments give the spectral luminosity, not the total luminosity. We
ature for the two spectra are 8 keV and 12 keV, respectively, use Equation (3.11) of Fransson et al. (1996) for the luminosity,
4
5. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 Chandra et al.
adjusting to an observed photon energy of ∼10 keV rather than column density in units of 1024 cm−1 and the line production is
100 keV; the Gaunt factor is increased to 2–3. For the pre-shock due to a central X-ray source in a spherical shell. The expression
column density, we use Equation (4.1) of Fransson et al. (1996). assumes a flux spectrum FE ∝ E −1 ; FE ∝ E −0.4 , which is more
These expressions allow for a variation of the pre-shock density appropriate to the hot thermal spectrum here, increases EWFe
∝ r −s , where s is a constant. The value s = 2 corresponds to a by 1.2. The prediction for the metallicity in our case in the early
steady wind and is commonly used, but implies stronger evolu- spectrum is EWFe = 0.1 keV, and the observed value is 0.2 keV.
tion than we observe in SN 2010jl. If the CSM around SN 2010jl In view of the uncertainties in the model and the observations,
is due to some pre-SN eruptive event, deviation from s = 2 is we consider the agreement to be adequate. At the second epoch,
plausible. Another parameter is m, determined by the expansion NH is smaller by a factor of three, so the strength of the Fe line
of the SN shock R ∝ t m . For the plausible value m = 0.8, we should be correspondingly smaller; this is consistent with the
find that s = 1.6 gives a reasonable representation of the lumi- nondetection of the line. The problem with this picture is that it
nosity and NH evolution. The implied value of the mass loss rate assumes Fe is in the low ionization stages that produce the Kα
˙ ˙
M, normalized to R = 1015 cm, is M−3 /vw2 ≈ 8v4 , where 0.6
line; this requires an ionization parameter ζ 5 (Kallman et al.
˙ ˙ −3 −1
M−3 = M/(10 M yr ), vw2 is the pre-shock wind velocity 2004), which is below the inferred value. One possibility is that
in units of 100 km s−1 , and v4 is the shock velocity in units of the circumstellar gas is clumped, with a density 40 times the
104 km s−1 at the first epoch. average; another is that the K line emission is from dense gas
The high temperature implies that we are observing the that is not along the line of sight.
forward shock region. The physical conditions are such that the A thermal fit to the low-temperature component implies an
forward shock front is close to the cooling regime (Chevalier & absorbing column density of (1.37 ± 8.44) × 1020 cm−2 , much
Irwin 2012). In this case, the luminosity of the forward shock less than the column to the hot component and consistent with
is expected to dominate that from the reverse shock and the the Galactic column density within the errors. This rules out the
reverse shock emission may be absorbed by a cooled shell, possibility that the cooler X-rays come from slow cloud shocks
which explains the lack of observational evidence for reverse in the clumpy CSM or from the reverse shocks. The component
shock emission. is also present in the second epoch. It could arise from a pre-SN
In modeling the X-ray absorption in SN 2010jl we have mass loss event or from an unrelated source in the direction
assumed that the absorbing gas is not fully ionized. If the of the SN. The components are best fit with either a thermal
circumstellar gas is photoionized by the X-ray emission, the component (T ∼ 1–2 keV) or a power law with Γ = 1.6–1.7.
absorption is reduced (e.g., Fransson 1982). Taking an X-ray The luminosities of this component in the 2010 December and
˙
luminosity of 1042 erg s−1 and M−3 /vw2 ≈ 8 (at r = 1015 cm), 2011 October spectra are 3.5×1039 erg s−1 and 5×1039 erg s−1 ,
the ionization parameter is ζ = L/nr 2 ≈ 200; a similar value respectively. The luminosity range and the power-law index
is obtained taking nr ∼ NH ∼ 1024 cm−2 and r = 6 × 1015 cm are compatible with a background ultraluminous X-ray source
for the early epoch. This is in a regime where the CNO elements (ULX), which can typically be described by an absorbed power-
may be completely ionized, but Fe is not (Hatchett et al. 1976). law spectrum (Swartz et al. 2004). Since the error in the flux
The CNO elements absorb radiation at ∼1 keV, so there is the determination is between 20%–30%, a factor of 1.4 change in
possibility of getting enhanced emission around that energy, as the luminosity at the two epochs is consistent with a constant
is observed in SN 2010jl. We investigated this possibility by flux. Thus we attribute this component to a background source,
running various cases with the CLOUDY photoionization code most likely a ULX, which is associated with the blue excess
(Ferland et al. 1998). It is possible to obtain cases in which emission region seen in the pre-SN HST images (Smith et al.
there is a peak at ∼1 keV, but they had too little absorption in 2011). We examined the HEASARC archives for useful limits
the 1.5–3 keV range. We thus favor a background source origin on such a source, but did not find any.
for the 1 keV emission, especially because the emission remains The 2010 December spectrum has only one temperature
fairly constant over the two epochs. component associated with the high column density. However,
The value of NH in 2010 December implies that τes ≈ 1, in the 2011 October spectrum, there are two temperature
where τes is the electron scattering optical depth through the pre- components associated with a high column density, one with
shock wind. The Hα line at that time showed roughly symmetric temperature 10 keV and another with temperature 1.1 keV.
broad wings (Smith et al. 2012) that are probably best explained The lower temperature component fits with 1/4 the column
by electron scattering in the slow moving wind. Chugai (2001) density of the high-temperature component. The fact that the
estimated that the broad features observed in SN 1998S require component is absent at the first epoch suggests that it is related to
τes ≈ (3–4). The required optical depth may be several times the SN emission. We examined the possibility that the emission
that observed along the line of sight to the X-ray emission, which is the result of reduced absorption due to photoionization of
could be the result of asymmetry. Andrews et al. (2011) found the absorbing material, in particular, that lighter atoms are
that the column density of dust needed for observed infrared ionized but heavier atoms are not. However, we were not able to
emission is larger than that on the line of sight to the SN, reproduce the observed emission and the source of this emission
although this is at larger radii. remains uncertain.
The 2010 December spectrum shows a 6.4 keV feature SN 2010jl is a special Type IIn SN because we have been able
(Figure 3), which is identified with the narrow Kα iron line. to catch it in X-rays early on with as sensitive an instrument
Since the 6.4 keV Fe line arises from neutral or low ionized iron as Chandra and trace the early X-ray evolution. We observe
(Fe i to Fe xi), it supports our finding that the radiation field is dramatic changes over two epochs separated by 10 months. For
not able to completely ionize the circumstellar gas. A simple the first time we see clear evidence of external CSM absorption
estimate of the expected equivalent width of the Fe line (EWFe ) in an SN. We also find that the CSM is not fully photoionized
can be obtained from Equation (5) of Kallman et al. (2004): by the SN emission, the SN is very luminous in X-rays, and the
EWFe = 0.3 (Z/Z )N24 keV, where N24 is the circumstellar temperature of the emitting gas is 10 keV.
5
6. The Astrophysical Journal Letters, 750:L2 (6pp), 2012 May 1 Chandra et al.
We are grateful to the referee for useful comments. Sup- Fransson, C., Lundqvist, P., & Chevalier, R. A. 1996, ApJ, 461, 993
port for this work was provided by NASA through Chandra Hatchett, S., Buff, J., & McCray, R. 1976, ApJ, 206, 847
Immler, S. 2007, in Supernova 1987A: 20 Years After, ed. S. Immler, K. Weiler,
Awards GO0-211080X and GO2-13082X issued by the Chandra & R. McCray (Melville, NY: AIP), 246
X-ray Observatory Center, which is operated by the Smithso- Immler, S., Milne, P., & Pooley, D. 2010, ATel, 3012, 1
nian Astrophysical Observatory for and on behalf of NASA Kallman, T. R., Palmeri, P., Bautista, M. A., Mendoza, C., & Krolik, J. H.
under contract NAS8-03060. 2004, ApJS, 155, 675
Kiewe, M., Gal-Yam, A., Arcavi, I., et al. 2012, ApJ, 744, 10
Facility: CXO Liedahl, D. A., Osterheld, A. L., & Goldstein, W. H. 1995, ApJ, 438, L115
Mewe, R., Gronenschild, E. H. B. M., & van den Oord, G. H. J. 1985, A&AS,
REFERENCES 62, 197
Newton, J., & Puckett, T. 2010, CBET, 2532, 1
Andrews, J. E., Clayton, G. C., Wesson, R., et al. 2011, AJ, 142, 45 Patat, F., Taubenberger, S., Benetti, S., Pastorello, A., & Harutyunyan, A.
Benetti, S., Bufano, F., Vinko, J., et al. 2010, CBET, 2536, 1 2011, A&A, 527, L6
Chevalier, R. A., & Irwin, C. M. 2012, ApJ, 747, L17 Smith, N., Li, W., Miller, A. A., et al. 2011, ApJ, 732, 63
Chugai, N. N. 2001, MNRAS, 326, 1448 Smith, N., Silverman, J. M., Filippenko, A. V., et al. 2012, AJ, 143, 17
Ferland, G. J., Korista, K. T., Verner, D. A., et al. 1998, PASP, 110, 761 Stoll, R., Prieto, J. L., Stanek, K. Z., et al. 2011, ApJ, 730, 34
Fransson, C. 1982, A&A, 111, 140 Swartz, D. A., Ghosh, K. K., Tennant, A. F., & Wu, K. 2004, ApJS, 154, 519
6