Uma equipe de astrônomos norte-americanos descobriu o par de buracos negros supermassivos mais próximos até agora no universo.
O par de buracos negros está localizado no centro do quasar chamado de PKS 1302-102, a aproximadamente 3.5 bilhões de anos-luz de distância.
Esses dois buracos negros estão separados de apenas uma semana-luz e estão num movimento espiral um em direção ao outro que deve acabar com uma colisão cataclísmica.
Em contraste, o par de buracos negros mais próximos descoberto até então estava separado de aproximadamente 20 anos-luz.
A kiloparsec scale_internal_shock_collision_in_the_jet_of_a_nearby_radio_galaxySérgio Sacani
Pesquisa feita com dados do Hubble mostram ondas de choque em colisão dentro dos chamados jatos extragalácticos emitidos pelos buracos negros supermassivos.
Directional Spreading Effect on a Wave Energy ConverterElliot Song
The results demonstrate the importance of tuning the WEC system for specific wave environments to harvest most energy and to avoid potential capsize due to hurricanes etc.
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
41 Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy ...Cristian Randieri PhD
Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy Electrons -The American Physical Society, Physical Review Letters, June 2010, Vol. 104, N. 24, pp. 241601-1-241601-5, ISSN: 0031-9007, doi: 10.1103/PhysRevLett.104.241601
di J. P. Bocquet, D. Moricciani, V. Bellini, M. Beretta, L. Casano, A. D'Angelo, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, V. G. Gurzadyan, A. Kashin, S. Knyazyan, A. Lapik, R. Lehnert, P. Levi Sandri, A. Lleres, F. Mammoliti, G. Mandaglio, M. Manganaro, A. Margarian, S. Mehrabyan, R. Messi, V. Nedorezov, C. Perrin, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, V. Vegna (2010)
Abstract
The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the ESRF's GRAAL facility constrains such anisotropies representing the first non-threshold collision-kinematics study of Lorentz violation. When interpreted within the minimal Standard-Model Extension, this result yields the two-sided limit of 1.6 x 10^{-14} at 95% confidence level on a combination of the parity-violating photon and electron coefficients kappa_{o+} and c. This new constraint provides an improvement over previous bounds by one order of magnitude.
A kiloparsec scale_internal_shock_collision_in_the_jet_of_a_nearby_radio_galaxySérgio Sacani
Pesquisa feita com dados do Hubble mostram ondas de choque em colisão dentro dos chamados jatos extragalácticos emitidos pelos buracos negros supermassivos.
Directional Spreading Effect on a Wave Energy ConverterElliot Song
The results demonstrate the importance of tuning the WEC system for specific wave environments to harvest most energy and to avoid potential capsize due to hurricanes etc.
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
41 Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy ...Cristian Randieri PhD
Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy Electrons -The American Physical Society, Physical Review Letters, June 2010, Vol. 104, N. 24, pp. 241601-1-241601-5, ISSN: 0031-9007, doi: 10.1103/PhysRevLett.104.241601
di J. P. Bocquet, D. Moricciani, V. Bellini, M. Beretta, L. Casano, A. D'Angelo, R. Di Salvo, A. Fantini, D. Franco, G. Gervino, F. Ghio, G. Giardina, B. Girolami, A. Giusa, V. G. Gurzadyan, A. Kashin, S. Knyazyan, A. Lapik, R. Lehnert, P. Levi Sandri, A. Lleres, F. Mammoliti, G. Mandaglio, M. Manganaro, A. Margarian, S. Mehrabyan, R. Messi, V. Nedorezov, C. Perrin, C. Randieri, D. Rebreyend, N. Rudnev, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, V. Vegna (2010)
Abstract
The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the ESRF's GRAAL facility constrains such anisotropies representing the first non-threshold collision-kinematics study of Lorentz violation. When interpreted within the minimal Standard-Model Extension, this result yields the two-sided limit of 1.6 x 10^{-14} at 95% confidence level on a combination of the parity-violating photon and electron coefficients kappa_{o+} and c. This new constraint provides an improvement over previous bounds by one order of magnitude.
The meaning of quantum mechanics becomes clearer when we restate Planck's constant and the gravitational constant in natural Planck units. These units reveal hidden structure that improves our understanding of physics and gives new meaning to fundamental ideas.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
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)
Magnetic interaction of_a_super_cme_with_the_earths_magnetosphere_scenario_fo...Sérgio Sacani
Solar eruptions, known as Coronal Mass Ejections (CMEs), are
frequently observed on our Sun. Recent Kepler observations of super
ares
on G-type stars have implied that so called super-CMEs, possessing kinetic
energies 10 times of the most powerful CME event ever observed on the Sun,
could be produced with a frequency of 1 event per 800-2000 yr on solar-
like slowly rotating stars. We have performed a 3D time-dependent global
magnetohydrodynamic simulation of the magnetic interaction of such a CME
cloud with the Earth's magnetosphere. We calculated the global structure
of the perturbed magnetosphere and derive the latitude of the open-closed
magnetic eld boundary. We also estimated energy
uxes penetrating the
Earth's ionosphere and discuss the consequences of energetic particle
uxes
on biological systems on early Earth.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
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)
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Mapping spiral structure on the far side of the Milky WaySérgio Sacani
Little is known about the portion of the Milky Way lying beyond the Galactic center at distances
of more than 9 kiloparsec from the Sun. These regions are opaque at optical wavelengths
because of absorption by interstellar dust, and distances are very large and hard to measure.
We report a direct trigonometric parallax distance of 20:4þ2:8
2:2 kiloparsec obtained with the Very
Long Baseline Array to a water maser source in a region of active star formation. These
measurements allow us to shed light on Galactic spiral structure by locating the ScutumCentaurus
spiral arm as it passes through the far side of the Milky Way and to validate a
kinematic method for determining distances in this region on the basis of transverse motions.
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)
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Uma questão fundamental na astrobiologia, é: se a vida pode ser transportada entre planetas extrassolares, e sistemas planetários? Uma equipe de astrofísicos norte-americanos propôs uma nova estratégia para responder a essa questão com base no princípio que a vida alienígena que surgiu via espalhamento – num processo chamado de panspermia – exibirá mais aglomerados do que a vida que surge espontaneamente.
Existem duas maneiras básicas para a vida ter se espalhado além de sua estrela hospedeira.
A primeira seria por meio de um processo natural de arremessamento de asteroides e cometas. A segunda seria por meio da vida inteligente que deliberadamente viajaria pelo espaço.
Um novo artigo, aceito para publicação no Astrophysical Journal Letters, não lida como a panspermia ocorre. Ele simplesmente pergunta: se ela ocorreu, nós poderíamos detectá-la? Em princípio, a resposta é sim.
O modelo desenvolvido pela equipe no Harvard-Smithsonian Center for Astrophysics assume que as sementes de um planeta vivo se espalham em todas as direções.
The abundance of_x_shaped_radio_sources_vla_survey_of_52_sources_with_off_axi...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
The meaning of quantum mechanics becomes clearer when we restate Planck's constant and the gravitational constant in natural Planck units. These units reveal hidden structure that improves our understanding of physics and gives new meaning to fundamental ideas.
The characterization of_the_gamma_ray_signal_from_the_central_milk_way_a_comp...Sérgio Sacani
Past studies have identified a spatially extended excess of ∼1-3 GeV gamma rays from the region
surrounding the Galactic Center, consistent with the emission expected from annihilating dark
matter. We revisit and scrutinize this signal with the intention of further constraining its characteristics
and origin. By applying cuts to the Fermi event parameter CTBCORE, we suppress the tails
of the point spread function and generate high resolution gamma-ray maps, enabling us to more
easily separate the various gamma-ray components. Within these maps, we find the GeV excess
to be robust and highly statistically significant, with a spectrum, angular distribution, and overall
normalization that is in good agreement with that predicted by simple annihilating dark matter
models. For example, the signal is very well fit by a 36-51 GeV dark matter particle annihilating to
b
¯b with an annihilation cross section of σv = (1−3)×10−26 cm3
/s (normalized to a local dark matter
density of 0.4 GeV/cm3
). Furthermore, we confirm that the angular distribution of the excess is
approximately spherically symmetric and centered around the dynamical center of the Milky Way
(within ∼0.05◦
of Sgr A∗
), showing no sign of elongation along the Galactic Plane. The signal is
observed to extend to at least ' 10◦
from the Galactic Center, disfavoring the possibility that this
emission originates from millisecond pulsars.
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)
Magnetic interaction of_a_super_cme_with_the_earths_magnetosphere_scenario_fo...Sérgio Sacani
Solar eruptions, known as Coronal Mass Ejections (CMEs), are
frequently observed on our Sun. Recent Kepler observations of super
ares
on G-type stars have implied that so called super-CMEs, possessing kinetic
energies 10 times of the most powerful CME event ever observed on the Sun,
could be produced with a frequency of 1 event per 800-2000 yr on solar-
like slowly rotating stars. We have performed a 3D time-dependent global
magnetohydrodynamic simulation of the magnetic interaction of such a CME
cloud with the Earth's magnetosphere. We calculated the global structure
of the perturbed magnetosphere and derive the latitude of the open-closed
magnetic eld boundary. We also estimated energy
uxes penetrating the
Earth's ionosphere and discuss the consequences of energetic particle
uxes
on biological systems on early Earth.
Exocometary gas in_th_hd_181327_debris_ringSérgio Sacani
An increasing number of observations have shown that gaseous debris discs are not an
exception. However, until now we only knew of cases around A stars. Here we present the first
detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with ALMA
observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric
disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with
radiative transfer calculations we study the dust and CO mass distribution. We find the dust is
distributed in a ring with a radius of 86:0 0:4 AU and a radial width of 23:2 1:0 AU. At
this frequency the ring radius is smaller than in the optical, revealing grain size segregation
expected due to radiation pressure. We also report on the detection of low level continuum
emission beyond the main ring out to 200 AU. We model the CO emission in the non-LTE
regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging
between 1:2 10 6 M and 2:9 10 6 M, depending on the gas kinetic temperature and
collisional partners densities. The CO densities and location suggest a secondary origin, i.e.
released from icy planetesimals in the ring. We derive a CO cometary composition that is
consistent with Solar system comets. Due to the low gas densities it is unlikely that the gas is
shaping the dust distribution.
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)
A highly magnetized twin-jet base pinpoints a supermassive black holeSérgio Sacani
Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical
models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could
be the case for NGC1052, to launch these jets. This requires magnetic fields on the order of 103 G to 104 G. We imaged the vicinity
of the SMBH of the AGN NGC1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is
smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the
magnetic field at 1 Schwarzschild radius to lie between 200 G and 8:3 104 G consistent with Blandford & Znajek models.
Mapping spiral structure on the far side of the Milky WaySérgio Sacani
Little is known about the portion of the Milky Way lying beyond the Galactic center at distances
of more than 9 kiloparsec from the Sun. These regions are opaque at optical wavelengths
because of absorption by interstellar dust, and distances are very large and hard to measure.
We report a direct trigonometric parallax distance of 20:4þ2:8
2:2 kiloparsec obtained with the Very
Long Baseline Array to a water maser source in a region of active star formation. These
measurements allow us to shed light on Galactic spiral structure by locating the ScutumCentaurus
spiral arm as it passes through the far side of the Milky Way and to validate a
kinematic method for determining distances in this region on the basis of transverse motions.
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)
PROBING FOR EVIDENCE OF PLUMES ON EUROPA WITH HST/STISSérgio Sacani
Roth et al. (2014a) reported evidence for plumes of water venting from a southern high latitude
region on Europa – spectroscopic detection of off-limb line emission from the dissociation
products of water. Here, we present Hubble Space Telescope (HST) direct images of Europa in
the far ultraviolet (FUV) as it transited the smooth face of Jupiter, in order to measure absorption
from gas or aerosols beyond the Europa limb. Out of ten observations we found three in which
plume activity could be implicated. Two show statistically significant features at latitudes similar
to Roth et al., and the third, at a more equatorial location. We consider potential systematic
effects that might influence the statistical analysis and create artifacts, and are unable to find any
that can definitively explain the features, although there are reasons to be cautious. If the
apparent absorption features are real, the magnitude of implied outgassing is similar to that of the
Roth et al. feature, however the apparent activity appears more frequently in our data.
Uma questão fundamental na astrobiologia, é: se a vida pode ser transportada entre planetas extrassolares, e sistemas planetários? Uma equipe de astrofísicos norte-americanos propôs uma nova estratégia para responder a essa questão com base no princípio que a vida alienígena que surgiu via espalhamento – num processo chamado de panspermia – exibirá mais aglomerados do que a vida que surge espontaneamente.
Existem duas maneiras básicas para a vida ter se espalhado além de sua estrela hospedeira.
A primeira seria por meio de um processo natural de arremessamento de asteroides e cometas. A segunda seria por meio da vida inteligente que deliberadamente viajaria pelo espaço.
Um novo artigo, aceito para publicação no Astrophysical Journal Letters, não lida como a panspermia ocorre. Ele simplesmente pergunta: se ela ocorreu, nós poderíamos detectá-la? Em princípio, a resposta é sim.
O modelo desenvolvido pela equipe no Harvard-Smithsonian Center for Astrophysics assume que as sementes de um planeta vivo se espalham em todas as direções.
The abundance of_x_shaped_radio_sources_vla_survey_of_52_sources_with_off_axi...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
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.
An evolucionary missing_link_a_modest_mass_early_type_galaxy_hosting_an_over_...Sérgio Sacani
O buraco negro supermassivo de uma galáxia descoberta recentemente é bem maior do seria possível, de acordo com as atuais teorias da evolução galáctica. Novo trabalho, realizado por astrônomos na Universidade Keele e da Universidade Central Lancashire, mostra que o buraco negro é muito massivo do que deveria ser, se comparado com a massa da galáxia ao redor. Os cientistas publicaram os resultados em um artigo no Monthly Notices of The Royal Astronomical Society.
A galáxia, SAGE0536AGN, foi inicialmente descoberta com o Telescópio Espacial Spitzer da NASA na luz infravermelha. Apesar de ter no mínimo 9 bilhões de anos de vida, ela contém um núcleo galáctico ativo, um AGN, um objeto incrivelmente brilhante resultante da acreção de gás por um buraco negro supermassivo central. O gás é acelerado a altíssimas velocidades devido ao imenso campo gravitacional do buraco negro, fazendo com que o gás emita luz.
A equipe agora também confirmou a presença de um buraco negro medindo a velocidade do gás movendo-se ao seu redor. Usando o Southern African LArge Telescope, os cientistas observaram que uma linha de emissão de hidrogênio, no espectro da galáxia (onde a luz é dispersada em suas diferentes cores – um efeito similar é visto usando um prisma) é alargada pelo Efeito Doppler, onde o comprimento de onda (a cor) da luz de um objeto é desviada para o azul e para o vermelho dependendo se ele está se movendo para perto ou para longe nós. O grau de alargamento implica que o gás está se movendo ao redor numa alta velocidade, um resultado do forte campo gravitacional do buraco negro.
An extreme starburst_in_the_core_of_a_rich_galaxy_cluster_at_z_1_7Sérgio Sacani
Os astrônomos descobriram um raro tipo de aglomerado de galáxias que tem seu coração repleto de novas estrelas. A descoberta inesperada, aconteceu com a ajuda dos telescópios espaciais da NASA Spitzer e Hubble, e sugere que galáxias gigantescas no núcleo desses aglomerados massivos podem crescer de maneira significante se alimentando de gás roubado de outras galáxias.
“Normalmente, as estrelas no centro dos aglomerados de galáxias, são velhas e mortas, essencialmente fósseis estelares”, disse Tracy Webb da Universidade McGill, em Montreal, no Canadá, principal autor do artigo que descreve as descobertas publicado na edição de 20 de Agosto do Teh Astrophysical Journal. “Mas nós acreditamos que a gigantesca galáxia no centro desse aglomerado está gerando novas estrelas de maneira furiosa depois de realizar uma fusão com uma galáxia menor”.
Os aglomerados de galáxias são grandes famílias de galáxias unidas e agrupadas pela gravidade. A nossa Via Láctea reside em um pequeno grupo de galáxias, chamado de Grupo Local, que por sua vez reside na periferia do gigantesco superaglomerado de galáxias Lanikea com 100000 galáxias (Lanikea signifiva “céu imensurável” em havaiano).
O aglomerado nesse novo estudo, é chamado pelos astrônomos de SpARCS1049+56, e tem no mínimo 27 galáxias, e uma massa combinada equivalente a 400 trilhões sóis. Ele está localizado a cerca de 9.8 bilhões de anos-luz na direção da constelação de Ursa Major. O objeto foi inicialmente descoberto usando o Spitzer e o Telescópio Canadá-França-Havaí, localizado no monte Mauna Kea no Havaí, e confirmado, usando o Observatório W.M. Keck, também no Mauna Kea.
Pares de buracos negros circulando um em relação ao outro, chegando cada vez mais perto até que eles se colidem, podem criar ondas no espaço-tempo, mas, uma nova pesquisa, sugere que essas ondas são mais leves do que se pensava anteriormente.
Um novo artigo pesquisando por sinais dessas ondas no espaço-tempo, conhecidas como ondas gravitacionais, veio do nada, sugerindo que os teóricos precisavam repensar seus modelos desses pares de monstros. O novo trabalho afeta a pesquisa por ondas gravitacionais usando pulsares, estrelas mortas que parecem criar pulso regulares de luz, não muito diferente do que acontece com um farol.
As ondas gravitacionais foram originalmente previstas por Albert Einstein, mas ninguém jamais encontrou evidências diretas da sua existência. O novo trabalho ajudará os cientistas a avançarem em suas pesquisas, e no caminho, essas pesquisas poderiam ajudar a identificar detalhes sobre a fusão das galáxias no universo.
The high mass_stelar_initial_mass_function_in_m31_clustersSérgio Sacani
Em uma pesquisa feita com o Telescópio Espacial Hubble da NASA, analisando imagens de 2753 jovens, aglomerados estelares azuis, na vizinha galáxia de Andrômeda, a M31, os astrônomos descobriram que a M31 e a nossa própria galáxia, possuem uma porcentagem similar de estrelas recém-nascidas, com base na massa estudada.
Identificando qual porcentagem de estrelas tem uma massa particular, dentro de um aglomerado, ou sua Função de Massa Inicial, IMF, os cientistas podem interpretar melhor a luz de galáxias distantes e entender a história de formação das estrelas no universo.
A intensa pesquisa, agrupou 414 mosaicos fotográficos feitos pelo Hubble da M31, uma colaboração única feita entre astrônomos, cientistas cidadãos, voluntários que forneceram uma ajuda valiosa em analisar a montanha de dados do Hubble.
“Dada a quantidade de imagens do Hubble, nosso estudo da IMF, não seria possível sem a ajuda dos cientistas cidadãos”, disse Daniel Weisz, da Universidade de Washington em Seatle. Weisz, é o principal autor do artigo que foi publicado no dia 20 de Junho no The Astrophysical Journal.
The abundance of_x_shpoaed_radio_sources_implications_for_the_gravitational_w...Sérgio Sacani
Devem existir menos buracos negros supermassivos binários nos núcleos das galáxias do que se pensava anteriormente, disse uma equipe de cientistas da Universidade de Brandeis em Waltaham, Massachussets, e do Instituto de Pesquisa Raman em Bangalore, na Índia.
A maior parte das galáxias massivas no universo devem abrigar no mínimo um buraco negro supermassivo em seus núcleos.
Quando duas galáxias colidem, seus buracos negros se juntam, formando uma dança colossal que resulta numa combinação de par. Esse processo é a mais intensa fonte de ondas gravitacionais no universo, que ainda precisam ser diretamente detectadas.
“As ondas gravitacionais representam a próxima fronteira da astrofísica, e sua detecção levará a novas ideias sobre o universo. É importante se ter a maior quantidade de informação possível sobre as fontes dessas ondas”, disse o Dr. David Roberts, um membro da equipe da Universidade de Brandeis.
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.
O Telescópio Espacial Hubble das agências espaciais, NASA e ESA fez imagens de três magníficas seções da Nebulosa do Véu em 1997. Agora, um novo conjunto de imagens espetaculares feitas com a Wide Field Camera 3 do Hubble captura essa bela remanescente estelar com detalhes novos e surpreendentes e revela sua expansão nos últimos anos.
Derivando seu nome da delicada estrutura filamentar, a bela Nebulosa do Véu, é uma das remanescentes de supernovas mais conhecidas. Ela se formou da violenta morte de uma estrela com uma massa vinte vezes maior que a massa do Sol que explodiu a cerca de 8000 anos atrás. Localizada a aproximadamente 2100 anos-luz da Terra, na constelação de Cygnus, o Cisne, essa nuvem brilhante e colorida de detritos brilhantes se espalha por aproximadamente 110 anos-luz.
Em 1997, a Wide Field and Planetary Camera 2 do Hubble, a WFPC2, fotografou a Nebulosa do Véu, fornecendo visões detalhadas da sua estrutura. Agora, sobrepondo as imagens da WFPC2 com os novos dados obtidos pela Wide Field Camera 3, a WFC3, os cientistas podem ter acesso a detalhes ainda maiores de modo que eles possam estudar como a nebulosa se expandiu desde que ela foi fotografada a 18 anos atrás.
O centro da nossa Via Láctea é um lugar misterioso. Não somente está a milhares de anos-luz de distância, mas está também escondido sob grande quantidade de poeira de modo que a maior parte das estrelas em seu interior são invisíveis. Pesquisadores de Harvard, estão propondo uma nova maneira de limpar a neblina e registrar as estrelas ali escondidas. Eles sugerem observar os comprimentos de onda de rádio provenientes das estrelas supersônicas.
“Existem muitas, nós não sabemos sobre o centro galáctico, e nós queremos aprender muito”, disse o principal autor do estudo Idan Ginsburg do Harvard-Smithsonian Center for Astrophysics (CfA). “Usando essa técnica, nós podemos encontrar estrelas que ninguém observou antes”.
A grande trajetória do centro da nossa galáxia para a Terra é repleta de tanta poeira que até mesmo dos trilhões de fótons de luz visível que veem em nossa direção, somente um fóton atingirá nossos telescópios. Ondas de rádio, de uma diferente parte do espectro eletromagnético, possui energia mais baixa e comprimentos de onda maiores. Elas podem passar pela poeira de forma ilesa.
A propable milli_parsec_supermassive_binary_black_hole_in_the_nearest_quasar_...Sérgio Sacani
Astrônomos usando o Telescópio Espacial Hubble da NASA descobriram que a Markarian 231 (Mrk 231), a galáxia mais próxima da Terra que abriga um quasar, é alimentada por dois buracos negros centrais girando violentamente um em relação ao outro.
A descoberta sugere que os quasares, os brilhantes núcleos das galáxias ativas, podem normalmente abrigar dois buracos negros centrais que caem, um na órbita do outro como resultado da fusão de duas galáxias. Como um par de patinadores, o buraco negro duplo gera uma tremenda quantidade de energia que faz o núcleo da galáxia que o abriga se sobrepor ao brilho da população de bilhões de estrelas da galáxia, que os cientistas então identificam como quasares.
Os cientistas procuraram nas observações de arquivo do Hubble feitas na radiação ultravioleta emitida do centro da Mrk 231 para descobrir o que eles descrevem como propriedades extremas e surpreendentes.
New m embers_of_the_tw_hydrae_association_and_two_accreting_m_dwarfs_in_scorp...Sérgio Sacani
Uma descoberta acidental de uma coleção de jovens estrelas do tipo anãs vermelhas perto do nosso Sistema Solar, poderiam nos dar uma rara ideia da formação planetária em câmera lenta. Os astrônomos da The Australian National University a ANU e a University of New South Wales, a UNSW, em Canberra, descobriram grandes discos de poeira ao redor de duas estrelas, mostrando sinais de planetas em processo de formação.
“Nós achamos que a Terra e todos os planetas se formaram de discos como esses, assim é fascinante ver um potencial novo sistema solar se formando”, disse o principal pesquisador Dr. Simon Murphy, da ANU Research School of Astronomy and Astrophysics.
“Contudo, outras estrelas dessa idade normalmente não têm mais discos. Os discos das anãs vermelhas parecem viver mais do que os de estrelas mais quentes como o Sol. Nós não entendemos por que”, disse o Dr. Murphy.
Direct imaging and_spectroscopy_of_a_young_extrasolar_kuiper_belt_in_the_near...Sérgio Sacani
O Cinturão de Kuiper, é a região do Sistema Solar situada além da órbita de Neturno, cerca de 40 UA (1 UA – Unidade Astronômica – é a distância média entre a Terra e o Sol). O Cinturão de Kuiper é o local de numeoroso planetas anões, como Plutão, e é também o lar de milhares de remanescentes das fases iniciais da formação de planetas congelados, que podem fornecer um entendimento fundamental, sobre o nosso Sistema Solar no início de sua vida. Para além do Cinturão de Kuiper, está a Nuvem de Oort, uma nuvem esférica de cometas e planetesimais congelados que se estende talvez a cem mil UA. Provavelmente outros sistemas planetários também contêm regiões análogas ao Cinturão de Kuiper, e elas poderiam ajudar a jogar uma luz sobre a evolução e composição do Cinturão de Kuiper do Sistema Solar. Até agora, contudo, os poucos anéis que se tem imageado não são análogos muito confiáveis, eles têm sido vistos ao redor de estrelas próximas, cujo ambiente de nascimento é diferente do complexo estelar massivo onde o Sol, provavelmente foi formado.
A situação recentemente mudou com o advento de uma nova geração de instrumentos de imageamento astronômico, acoplados aos grandes telescópios que usam sistemas de óptica adaptativa para obter imagens com uma alta resolução espacial. O astrônomo Scott Kenyon do CfA e seus colegas usou o novo espectrômetro montado no Telescópio Gemini para estudar uma estrela um pouco maior que o Sol localizada a cerca de 360 anos-luz de distância num complexo relativamente novo de estrelas massivas, uma região aproximadamente parecida com o suposto local de nascimento do Sol. A estrela tem um grande excesso de emissão infravermelha, uma indicação clara que ela abriga um disco de poeira circunstelar que possivelmente está formando um sistema de planetas.
Os astrônomos imagearam o disco, e encontraram que o anel de detritos está confinado a uma estrutura parecida com o Cinturão de Kuiper. Além disso, eles descobriram a partir do espectro da luz refletida que sua poeira tem propriedades consistentes com os maiores constituintes do Cinturão de Kuiper, incluindo gelo de água. O resultado fornece uma referência promissora para se entender a evolução e a composição do Cinturão de Kuiper, e, para se entender também a evolução inicial do Sistema Solar.
Uma espetacular colisão de galáxias foi descoberta além da Via Láctea. O sistema mais próximo já descoberto, a identificação foi anunciada por uma equipe de astrônomos liderada pelo Professor Quentin Parker da Universidade de Hong Kong e pelo Professor Albert Zijlstra na Universidade de Manchester.
A galáxia está a 30 milhões de anos-luz de distância, o que significa que ela é relativamente próxima. Ela foi chamada de Roda de Kathryn, em homenagem à sua semelhança com o famoso fogo de artifício e também em homenagem à esposa do coautor do trabalho.
Esses sistemas são muito raros e nascem da colisão entre duas galáxias de tamanhos similares. As ondas de choque geradas na colisão comprimem o reservatório de gás em cada galáxia e disparam a formação de novas estrelas. Isso cria um espetacular anel de intensa emissão, e ilumina o sistema, do mesmo modo que a Roda Catherine ilumina a noite num show de fogos de artifício.
As galáxias crescem através de colisões, mas é raro registrar esse processo acontecendo, e é extremamente raro ver o anel da colisão em progresso. Pouco mais de 20 sistemas com anéis completos são conhecidos.
The xmm newton-view_of_the_central_degrees_of_the_milk_waySérgio Sacani
Novas imagens do Observatório de Raios-X XMM-Newton da ESA revelaram alguns dos processos mais intensos que acontecem no coração da nossa Via Láctea.
As fontes brilhantes e pontuais que se destacam por toda imagem indicam os sistemas estelares binários onde uma das estrelas atingiu o final de sua vida, desenvolvendo para um objeto compacto e denso – uma estrela de nêutrons ou um buraco negro.
A região central da Via Láctea também contém jovens estrelas e aglomerados estelares e algumas dessas fontes são visíveis como pontos brancos e vermelhos brilhando na imagem, que se espalha por 1000 anos-luz.
A maior parte da ação ocorre no centro, onde nuvens difusas de gás estão sendo cavadas por ventos poderosos soprados por estrelas jovens, bem como por supernovas.
Dark side of_comet_67_p_churyumov_gerasiemnko_in_august_october_2014Sérgio Sacani
Usando o instrumento Microwave Instrument for Rosetta Orbiter (MIRO), os cientistas estão estudando a região polar sul do cometa no final de sua longa estação de inverno. Os dados sugerem que essas regiões frias e escuras abrigam gelo nas suas primeiras dezenas de centímetros abaixo da superfície em quantidades muito maiores do que as encontradas em outras áreas do cometa.
Desde a sua chegada no Cometa 67P/Churyumov-Gerasimenko, a Rosetta tem pesquisado a superfície e o ambiente desse corpo de forma curiosa. Mas por um longo período de tempo, uma porção do núcleo, as regiões frias e escuras ao redor do polo sul do cometa, permaneceram inacessíveis para quase todos os instrumentos a bordo da sonda.
Devido a uma combinação de sua forma em lobo duplo e a inclinação do seu eixo de rotação, o cometa da Rosetta, tem um padrão sazonal muito peculiar durante a sua órbita de 6.5 anos. As estações estão distribuídas de maneira muito assimétrica entre os dois hemisférios, cada um deles compreende parte tanto dos lobos como do pescoço do cometa.
Na maior parte da órbita do cometa, o hemisfério norte experimenta um verão muito longo, durando cerca de 5.5 anos, e o hemisfério sul passa por um longo, frio e escuro inverno. Contudo, poucos meses antes do cometa passar pelo seu periélio, o ponto na sua órbita, mais próximo do Sol, a situação muda, e o hemisfério sul passa por um breve porém quente verão.
First results from_the_hubble_opal_program_jupiter_in_2015Sérgio Sacani
Os cientistas usando o Telescópio Espacial Hubble da NASA/ESA produziram novos mapas de Júpiter, que mostram as contínuas mudanças que ocorrem com a famosa Grande Mancha Vermelha. As imagens também revelam uma rara estrutura em forma de onda na atmosfera do planeta que não tinha sido vista por décadas. A nova imagem é a primeira de uma série de retratos anuais dos planetas externos do Sistema Solar, que nos darão um novo olhar desses mundos remotos, e ajudarão os cientistas a estudarem como eles mudam com o passar do tempo.
Nessa nova imagem de Júpiter, uma grande quantidade de feições foi capturada incluindo ventos, nuvens e tempestades. Os cientistas por trás dessas novas imagens, as obtiveram usando a Wide Field Camera 3 do Hubble, num período de observação de mais de 10 horas e produziram assim dois mapas completos do planeta, a partir das suas observações. Esses mapas fizeram com que fosse possível determinar a velocidade dos ventos em Júpiter, com a finalidade de identificar diferentes fenômenos na sua atmosfera além de traquear as suas feições mais famosas.
As novas imagens confirmam que a grande tempestade que tem existido na superfície de nuvens de Júpiter por no mínimo 300 anos, continua a encolher, mas mesmo que desapareça, ela irá morrer lutando. A tempestade, conhecida como Grande Mancha Vermelha, é vista aqui fazendo seus movimentos em espiral no centro da imagem do planeta. Ela tem diminuído de tamanho de maneira muito rápida de ano em ano. Mas agora, a taxa de encolhimento parece ter reduzido novamente, mesmo apesar da mancha ser cerca de 240 quilômetros menor do que era em 2014.
Pulsar emission amplified and resolved by plasma lensing in an eclipsing binarySérgio Sacani
Radio pulsars scintillate because their emission travels through the
ionized interstellar medium along multiple paths, which interfere
with each other. It has long been realized that, independent of their
nature, the regions responsible for the scintillation could be used
as ‘interstellar lenses’ to localize pulsar emission regions1,2
. Most
such lenses, however, resolve emission components only marginally,
limiting results to statistical inferences and detections of small
positional shifts3–5
. As lenses situated close to their source offer
better resolution, it should be easier to resolve emission regions of
pulsars located in high-density environments such as supernova
remnants6
or binaries in which the pulsar’s companion has an
ionized outflow. Here we report observations of extreme plasma
lensing in the ‘black widow’ pulsar, B1957+20, near the phase in its
9.2-hour orbit at which its emission is eclipsed by its companion’s
outflow7–9
. During the lensing events, the observed radio flux is
enhanced by factors of up to 70–80 at specific frequencies. The
strongest events clearly resolve the emission regions: they affect the
narrow main pulse and parts of the wider interpulse differently. We
show that the events arise naturally from density fluctuations in
the outer regions of the outflow, and we infer a resolution of our
lenses that is comparable to the pulsar’s radius, about 10 kilometres.
Furthermore, the distinct frequency structures imparted by the
lensing are reminiscent of what is observed for the repeating fast
radio burst FRB 121102, providing observational support for the
idea that this source is observed through, and thus at times strongly
magnified by, plasma lenses10
Wind from the_black_hole_accretion_disk_driving_a_molecular_outflow_in_an_act...Sérgio Sacani
Artigo descreve estudo inédito que mostra que os ventos gerados pelos buracos negros nos centros das galáxias pode acabar com o processo de formação de estrelas nas galáxias hospedeiras.
Artigo que descreve o trabalho feito com o Chandra nos aglomerados de galáxias de Perseus e Virgo sobre a descoberta de uma turbulência cósmica que impede a formação de novas estrelas.
Saturns fast spin_determined_from_its_gravitational_field_and_oblatenessSérgio Sacani
ARtigo descreve o novo método usado para determinar com precisão o período de rotação do planeta Saturno. Uma das grandes questões da astronomia. De acordo com o artigo o período de rotação de Saturno é de 10 horas 32 minutos e 45 segundos (+/- 46 segundos).
SPECTROSCOPIC CONFIRMATION OF THE EXISTENCE OF LARGE, DIFFUSE GALAXIES IN THE...Sérgio Sacani
We recently identified a population of low surface brightness objects in the field of the z = 0.023 Coma cluster,
using the Dragonfly Telephoto Array. Here we present Keck spectroscopy of one of the largest of these “ultradiffuse
galaxies” (UDGs), confirming that it is a member of the cluster. The galaxy has prominent absorption
features, including the Ca II H+K lines and the G-band, and no detected emission lines. Its radial velocity of
cz=6280±120 km s−1 is within the 1σ velocity dispersion of the Coma cluster. The galaxy has an effective
radius of 4.3 ± 0.3 kpc and a Sérsic index of 0.89 ± 0.06, as measured from Keck imaging. We find no indications
of tidal tails or other distortions, at least out to a radius of ∼2re. We show that UDGs are located in a previously
sparsely populated region of the size—magnitude plane of quiescent stellar systems, as they are ∼6 mag fainter
than normal early-type galaxies of the same size. It appears that the luminosity distribution of large quiescent
galaxies is not continuous, although this could largely be due to selection effects. Dynamical measurements are
needed to determine whether the dark matter halos of UDGs are similar to those of galaxies with the same
luminosity or to those of galaxies with the same size.
The shadow _of_the_flying_saucer_a_very_low_temperature_for_large_dust_grainsSérgio Sacani
Os astrónomos usaram o ALMA e os telescópios do IRAM para fazer a primeira medição direta da temperatura dos grãos de poeira grandes situados nas regiões periféricas de um disco de formação planetária que se encontra em torno de uma estrela jovem. Ao observar de forma inovadora um objeto cujo nome informal é Disco Voador, os astrónomos descobriram que os grãos de poeira são muito mais frios do que o esperado: -266º Celsius. Este resultado surpreendente sugere que os modelos teóricos destes discos precisam de ser revistos.
Uma equipa internacional liderada por Stephane Guilloteau do Laboratoire d´Astrophysique de Bordeaux, França, mediu a temperatura de enormes grãos de poeira que se encontram em torno da jovem estrela 2MASS J16281370-2431391 na região de formação estelar Rho Ophiuchi, a cerca de 400 anos-luz de distância da Terra.
Esta estrela encontra-se rodeada por um disco de gás e poeira — chamado disco protoplanetário, uma vez que se encontra na fase inicial da formação de um sistema planetário. Este disco é visto de perfil quando observado a partir da Terra e a sua aparência em imagens no visível levou a que se lhe desse o nome informal de Disco Voador.
Os astrónomos utilizaram o ALMA para observar o brilho emitido pelas moléculas de monóxido de carbono no disco da 2MASS J16281370-2431391. As imagens revelaram-se extremamente nítidas e descobriu-se algo estranho — em alguns casos o sinal recebido era negativo. Normalmente um sinal negativo é fisicamente impossível, mas neste caso existe uma explicação, que leva a uma conclusão surpreendente.
Is the remnant of GW190425 a strange quark star?Sérgio Sacani
This study investigates the effects of different QCD models on the structure of strange quark
stars (SQS). In these models, the running coupling constant has a finite value in the infrared region
of energy. By imposing some constraints on the strange quark matter (SQM) and exploiting the
analytic and background perturbation theories, the equations of states for the SQM are obtained.
Then, the properties of SQSs in general relativity are evaluated. By using component masses of
GW190425 [1] as well as some conversion relations between the baryonic mass and the gravitational
mass, the remnant mass of GW190425 is obtained. Our results for the maximum gravitational
mass of SQS are then compared with the remnant mass of GW190425. The results indicate that
the obtained maximum gravitational masses are comparable to the remnant mass of GW190425.
Therefore, it is proposed that the remnant mass of GW190425 might be a SQS.
Forming intracluster gas in a galaxy protocluster at a redshift of 2.16Sérgio Sacani
Galaxy clusters are the most massive gravitationally bound structures in the Universe, comprising thousands of galaxies and
pervaded by a diffuse, hot “intracluster medium” (ICM) that dominates the baryonic content of these systems. The formation
and evolution of the ICM across cosmic time1
is thought to be driven by the continuous accretion of matter from the large-scale
filamentary surroundings and dramatic merger events with other clusters or groups. Until now, however, direct observations of
the intracluster gas have been limited only to mature clusters in the latter three-quarters of the history of the Universe, and we
have been lacking a direct view of the hot, thermalized cluster atmosphere at the epoch when the first massive clusters formed.
Here we report the detection (about 6σ) of the thermal Sunyaev-Zeldovich (SZ) effect2
in the direction of a protocluster. In fact,
the SZ signal reveals the ICM thermal energy in a way that is insensitive to cosmological dimming, making it ideal for tracing
the thermal history of cosmic structures3
. This result indicates the presence of a nascent ICM within the Spiderweb protocluster
at redshift z = 2.156, around 10 billion years ago. The amplitude and morphology of the detected signal show that the SZ
effect from the protocluster is lower than expected from dynamical considerations and comparable with that of lower-redshift
group-scale systems, consistent with expectations for a dynamically active progenitor of a local galaxy cluster.
Resolved imaging confirms a radiation belt around an ultracool dwarfSérgio Sacani
Radiation belts are present in all large-scale Solar System planetary
30 magnetospheres: Earth, Jupiter, Saturn, Uranus, and Neptune1. These persistent
31 equatorial zones of relativistic particles up to tens of MeV in energy can extend farther
32 than 10 times the planet’s radius, emit gradually varying radio emissions2–4 and impact
33 the surface chemistry of close-in moons5. Recent observations demonstrate that very low
34 mass stars and brown dwarfs, collectively known as ultracool dwarfs, can produce planet35
like radio emissions such as periodically bursting aurorae6–8 from large-scale
36 magnetospheric currents9–11. They also exhibit slowly varying quiescent radio
37 emissions7,12,13 hypothesized to trace low-level coronal flaring14,15 despite departing from
38 empirical multi-wavelength flare relationships8,15. Here we present high resolution
39 imaging of the ultracool dwarf LSR J1835+3259 at 8.4 GHz demonstrating that its
40 quiescent radio emission is spatially resolved and traces a double-lobed and axisymmetric
41 structure similar in morphology to the Jovian radiation belts. Up to 18 ultracool dwarf
42 radii separate the two lobes, which are stably present in three observations spanning
43 more than one year. For plasma confined by the magnetic dipole of LSR J1835+3259, we
44 estimate 15 MeV electron energies consistent with Jupiter’s radiation belts4. Our results
45 confirm recent predictions of radiation belts at both ends of the stellar mass sequence8,16–
46 19 and support broader re-examination of rotating magnetic dipoles in producing non47
thermal quiescent radio emissions from brown dwarfs7, fully convective M dwarfs20, and
4
Dense m agnetized_plasma_associated_with_afast_radio_burstSérgio Sacani
Astrônomos detectaram uma chamada rápida explosão de rádio a cerca de 6 bilhões de anos-luz de distância, uma das menos de duas dezenas desse tipo de evento descobertos nos últimos dez anos, e dessa vez eles têm pistas sobre a fonte.
As rápidas explosões de rádio, ou FRBs, são misteriosas explosões de energia que ocorrem no espaço e que aparecem como rápidos flashes de ondas de rádio nos telescópios da Terra. Essas explosões têm intrigado os astrônomos desde que elas foram reportadas pela primeira vez a uma década atrás. Embora somente 16 dessas explosões tenham sido registradas, eles acreditam que possam existir milhares delas por dia.
Vasculhando mais de 650 horas de dados obtidos pelo Telescópio Green Bank, do NRAO, um grupo internacional de astrônomos descobriu o mais detalhado registro já feito até hoje de uma FRB.
Similar to Relativistic boost as_the_cause_of_periodicity_in_a_massive_black_hole_binary_candidate (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.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
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
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
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
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(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
1. Relativistic boost as the cause of periodicity in a massive
black-hole binary candidate
Daniel J. D’Orazio1
, Zolt´an Haiman1
& David Schiminovich1
To appear as a Letter in the September 17, 2015 isse of Nature
1
Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027
Because most large galaxies contain a central black hole, and galaxies often merge1
, black-
hole binaries are expected to be common in galactic nuclei2
. Although they cannot be imaged,
periodicities in the light curves of quasars have been interpreted as evidence for binaries3–5
,
most recently in PG 1302-102, with a short rest-frame optical period of 4 yr6
. If the orbital
period matches this value, then for the range of estimated black hole masses the components
would be separated by 0.007-0.017 pc, implying relativistic orbital speeds. There has been
much debate over whether black hole orbits could be smaller than 1 pc7
. Here we show that
the amplitude and the sinusoid-like shape of the variability of PG 1302-102 can be fit by
relativistic Doppler boosting of emission from a compact, steadily accreting, unequal-mass
binary. We predict that brightness variations in the ultraviolet light curve track those in the
optical, but with a 2-3 times larger amplitude. This prediction is relatively insensitive to the
details of the emission process, and is consistent with archival UV data. Follow-up UV and
optical observations in the next few years can test this prediction and confirm the existence
of a binary black hole in the relativistic regime.
Assuming PG 1302-102 is a binary, it is natural to attribute its optical emission to gas that
is bound to each black hole, forming circumprimary and circumsecondary accretion flows. Such
flows, forming “minidisks”, are generically found in high-resolution 2D and 3D hydrodynamical
simulations that include the black holes in their simulated domain8–15
. Assuming a circular orbit,
the velocity of the lower-mass secondary black hole is
v2 =
2π
1 + q
GM
4π2P
1/3
= 8, 500
1.5
1 + q
M
108.5M
1/3
P
4.04 yr
−1/3
km s−1
,
or ∼ 0.03c for the fiducial parameters above, where M = M1 + M2 is the total binary mass, M1,2
are the individual masses, q = M2/M1 ≤ 1 is the mass ratio, P is the orbital period, and c is the
speed of light. The primary’s orbital velocity is v1 = qv2. Even if a minidisk has a steady intrinsic
rest-frame luminosity, its apparent flux on Earth is modulated by relativistic Doppler beaming. The
photon frequencies suffer relativistic Doppler shift by the factor D = [Γ(1 − β||)]−1
, where Γ =
(1−β2
)−1/2
is the Lorentz factor, β = v/c is the three-dimensional velocity v in units of the speed
of light, and β|| = β cos φ sin i is the component of the velocity along the line of sight, with i and φ
the orbital inclination and phase. Because the photon phase-space density ∝ Fν/ν3
is invariant in
special relativity, the apparent flux Fν at a fixed observed frequency ν is modified from the flux of
1
arXiv:1509.04301v1[astro-ph.HE]14Sep2015
2. a stationary source F0
ν to Fν = D3
F0
D−1ν = D3−α
F0
ν . The last step assumes an intrinsic power-law
spectrum F0
ν ∝ να
. To first order in v/c, this causes a sinusoidal modulation of the apparent flux
along the orbit, by a fractional amplitude ∆Fν/Fν = ±(3 − α)(v cos φ/c) sin i. Although light-
travel time modulations appear at the same order, they are subdominant to the Doppler modulation.
This modulation is analogous to periodic modulations from relativistic Doppler boost predicted16
and observed for extrasolar planets17,18
and for a double white dwarf binary19
, but here it has a
much higher amplitude.
The light-curve of PG 1302-102 is well measured over approximately two periods (≈ 10
years). The amplitude of the variability is ±0.14 mag (measured in the optical V band20
), corre-
sponding to ∆Fν/Fν = ±0.14. The spectrum of PG 1302-102 in and around the V band is well
approximated by a double power-law, with α ≈ 0.7 (between 0.50−0.55µm) and α ≈ 1.4 (between
0.55 − 0.6µm), apart from small deviations caused by broad lines. We obtain an effective single
slope αopt = 1.1 over the entire V band. We conclude that the 14% variability can be attributed to
relativistic beaming for a line-of-sight velocity amplitude of v sin i = 0.074 c = 22, 000 km s−1
.
While large, this velocity can be realised for a massive (high M) but unequal-mass (low q)
binary, whose orbit is viewed not too far from edge-on (high sin i). In Fig. 1, we show the required
combination of these three parameters that would produce a 0.14 mag variability in the sum-total of
Doppler-shifted emission from the primary and the secondary black hole. As the figure shows, the
required mass is >∼109.1
M , consistent with the high end of the range inferred for PG 1302-102.
The orbital inclination can be in the range of i = 60 − 90◦
. The mass ratio q has to be low q <∼0.3,
which is consistent with expectations based on cosmological galaxy merger models21
, and also
with the identification of the optical and binary periods (for q >∼0.3, hydrodynamical simulations
would have predicted that the mass accretion rates fluctuate with a period several times longer than
the orbital period22
).
As Fig. 1 shows, fully accounting for the observed optical variability also requires that the
bulk (f2 >∼80%) of the optical emission arises from gas bound to the faster-moving secondary black
hole. We find that this condition is naturally satisfied for unequal-mass black holes. Hydrodynam-
ical simulations have shown that in the mass ratio range 0.03 <∼q <∼0.1, the accretion rate onto the
secondary is a factor of 10 − 20 higher than onto the primary13
. Because the secondary captures
most of the accreting gas from the circumbinary disk, the primary is “starved”, and radiates with
a much lower efficiency. In the (M, q) ranges favoured by the beaming scenario, we find that the
primary contributes less than 1%, and the circumbinary disk contributes less than 20% to the to-
tal luminosity, leaving the secondary as the dominant source of emission in the three–component
system (see details in Methods).
The optical light curve of PG 1302-102 appears remarkably sinusoidal compared to the best-
studied previous quasi-periodic quasar binary black hole candidate, which shows periodic bursts4
.
Nevertheless, the light curve shape deviates from a pure sinusoid. In order to see if such devia-
tions naturally arise within our model, we maximised the Bayesian likelihood over five parameters
(period P, velocity amplitude K, eccentricity e, argument of pericentre ω, and an arbitrary ref-
2
3. erence time t0) of a Kepler orbit23
and fit the observed optical light-curve. In this procedure, we
accounted for additional stochastic physical variability with a broken power-law power spectrum
(i.e. a “damped random walk” 24
) described by two additional parameters. This analysis indeed re-
turns a best-fit with a non-zero eccentricity of e = 0.09+0.07
−0.06, although a Bayesian criterion does not
favor this model over a pure sinusoid with fewer parameters (see Methods). We have considered an
alternative model to explain PG 1302-102’s optical variability, in which the luminosity variations
track the fluctuations in the mass accretion rate predicted in hydrodynamical simulations9–11,13,25
.
However, the amplitude of these hydrodynamic fluctuations are large (order unity), and their shape
is bursty, rather than sinusoid-like11,13,15
; as a result, we find that they provide a poorer fit to the
observations (see Fig. 2 and Methods). Furthermore, for mass ratios q >∼0.05, hydrodynamical
simulations predict a characteristic pattern of periodicities at multiple frequencies, but an analysis
of the periodogram of PG 1302-102 has not uncovered evidence for multiple peaks26
.
A simple observational test of relativistic beaming is possible due to the strong frequency-
dependence of PG 1302-102’s spectral slope α = d ln Fν/d ln ν. PG 1302-102’s continuum spec-
trum is nearly flat with a slope βFUV ≡ d ln Fλ/d ln λ = 0 in the far UV (0.145-0.1525µm) band,
and shows a tilt with βNUV = −0.95 in the 0.20-0.26µm near UV range (see Fig. 3 and Methods).
These translate to αFUV = −2 and αNUV = −1.05 in these bands, compared to the value α = 1.1
in the optical. The UV emission can be attributed to the same minidisks responsible for the optical
light, and would therefore share the same Doppler shifts in frequency. These Doppler shifts would
translate into UV variability that is larger by a factor of (3 − α)FUV/(3 − α)opt = 5/1.9 = 2.63
and (3 − α)NUV/(3 − α)opt = 4.05/1.9 = 2.13 compared to the optical, and reach the maximum
amplitudes of ±37% (FUV) and 30% (NUV).
PG 1302-102 has five separate UV spectra dated between 1992 and 2011, taken with instru-
ments on the Hubble Space Telescope (HST) and on the GALEX satellite (see Fig. 3), as well as ad-
ditional photometric observations with GALEX at 4 different times between 2006 and 2009 (shown
in Fig. 2). The brightness variations in both the far– and near–UV bands show variability resem-
bling the optical variability, but with a larger amplitude. Adopting the parameters of our best–fit
sinusoid model, and allowing only the amplitude to vary, we find that the UV data yields the best–
fit variability amplitudes of ∆Fν/Fν |FUV= ±(35.0 ± 3.9)% and ∆Fν/Fν |NUV= ±(29.5 ± 2.4)%
(shown in Fig. 2). These amplitudes are factors of (2.57 ± 0.28) and (2.17 ± 0.17) higher than in
the optical, in excellent agreement with the values 2.63 and 2.13 expected from the corresponding
spectral slopes.
Relativistic beaming provides a simple and robust explanation of PG 1302-102’s optical
periodicity. The prediction that the larger UV variations should track the optical light-curve can be
tested rigorously in the future with measurements of the optical and UV brightness at or near the
same time, repeated two or more times, separated by a few months to ∼ 2 years, covering up to
half of the optical period. A positive result will constitute the first detection of relativistic massive
black hole binary motion; it will also serve as a confirmation of the binary nature of PG 1302-102,
remove the ambiguity in the orbital period, and tightly constrain the binary parameters to be close
to those shown in Fig. 1.
3
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5. 17. van Kerkwijk, M. H. et al. Observations of Doppler Boosting in Kepler Light Curves. Astro-
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CoRoT-3 lightcurve. Astron. Astrophys. 521, L59 (2010).
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22. D’Orazio, D. J., Haiman, Z., Farris, B. D., MacFadyen, A. & Duffell, P. A reduced orbital
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Driven by Thermal Fluctuations? Astrophys. J. 698, 895–910 (2009).
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Acknowledgements The authors thank Matthew Graham, Jules Halpern, Adrian Price-Whelan, Jeff An-
drews, Maria Charisi, and Eliot Quataert for useful discussions. We also thank M. Graham for providing
the optical data in electronic form. This work was supported by the National Science Foundation Graduate
Research Fellowship under Grant No. DGE1144155 (D.J.D.) and by NASA grant NNX11AE05G (to Z.H.).
Contributions Z.H. conceived and supervised the project, performed the orbital velocity calculations, and
wrote the first draft of the paper. D.J.D. computed the emission models and performed the fits to the observed
light-curve. D.S. analysed the archival UV data. All authors contributed to the text.
Competing Interests The authors declare that they have no competing financial interests.
Correspondence Correspondence and requests for materials should be addressed to Z.H.
(email: zoltan@astro.columbia.edu).
5
7. Figure 1 | Binary parameters producing the optical flux variations of PG 1302-102 by
relativistic boost. Shaded regions mark combinations of binary mass M, mass ratio
q = M2/M1, and inclination i causing >13.5% flux variability (or line-of-sight velocity
amplitude (v/c) sin i ≥ 0.07), computed from the Doppler factor D3−α
with the effective
spectral slope of α = 1.1 in the V band, including emission from the primary, as well as
from the secondary black hole. The three panels assume fractions f2 = 1.0, 0.95, or 0.8
of the total luminosity arising from the secondary black hole; these values are consistent
with fractions found in hydrodynamical simulations13
(see Methods).
7
8. 0 1000 2000 3000 4000 5000 6000 7000
MJD-49100
14.4
14.6
14.8
15.0
15.2
Magnitude
Figure 2 | The optical and UV light-curve of PG 1302-102. Black points with 1σ errors
are optical data6
, superimposed with a best-fitting sinusoid (red dashed curve). The solid
black curve shows the best–fit relativistic light–curve. The blue dashed curve shows the
best-fit model obtained by scaling the mass-accretion rate found in a hydrodynamical
simulation of an unequal-mass (q = 0.1) binary11
. The additional circular data points with
1σ errors show archival near-UV (red) and far-UV (blue) spectral observations; the red
triangles show archival photometric near-UV data-points (see Fig. 3). The UV data include
an arbitrary overall normalisation to match the mean optical brightness. The dotted red
and blue curves show the best-fit relativistic optical light curve with amplitude scaled up
by factors of 2.17 and 2.57, which best match the NUV and FUV data, respectively.
8
9. Figure 3 | Archival ultraviolet spectra of PG 1302-102 from 1992-2011. Far- and near-
UV spectra obtained by the FOS and STIS instruments on the Hubble Space Telescope
(HST) and by GALEX are shown. Dates are in MJD (modified Julian day)-49100. Vertical
yellow bands mark regions outside the spectroscopic range of both GALEX and HST and
contain no useful spectral data. From each spectrum, average flux measurements were
computed in one or both of the two UV bands (shown in Fig. 2). GALEX photometric band
shapes for FUV and NUV photometry are shown for reference as shaded blue and red
curves, respectively. Additional GALEX NUV photometric data were also used in Fig. 2.
The UV spectra show an offset by as as much as ±30%, close to the value expected from
relativistic boost (see Methods).
9
10. METHODS
V-band emission from a three–component system in PG 1302-102. Here we assume that the
PG 1302-102 supermassive black hole (SMBH) binary system includes three distinct luminous
components: a circumbinary disk (CBD), as well as an actively accreting primary and secondary
SMBH. The optical brightness of each of the three components can be estimated once their accre-
tion rates and the BH masses M1 and M2 are specified. Using the absolute V-band magnitude of
PG 1302-102, MV = −25.81 and applying a bolometric correction BC ≈ 10, 27
we infer the total
bolometric luminosity of Lbol = 6.5(BC/10)×1046
erg s−1
. Bright quasars with the most massive
SMBHs (M >∼109
M ), have a typical radiative efficiency of = 0.3 28
. Adopting this value, the
implied accretion rate is ˙Mtot = Lbol/( c2
) = 3.7 M yr−1
.
We identify this as the total accretion rate through the CBD, and require that at small radii,
the rate is split between the two black holes ˙Mtot = ˙M2 + ˙M1 with the ratio η ≡ ˙M2/ ˙M1.
Hydrodynamical simulations13
have found that the secondary captures the large majority of the
gas, with 10 <∼η <∼20 for 0.03 <∼q <∼0.1 (where q ≡ M2/M1). Defining the Eddington ratio of
the ith
disk as its accretion rate scaled by its Eddington–limited rate fi,Edd ≡ ˙Mi/ ˙Mi,Edd with
˙MEdd ≡ LEdd/0.1c2
(here LEdd is the Eddington luminosity for the ith
BH, and we have adopted
the fiducial radiative efficiency of 0.1 to be consistent with the standard definition in the literature),
we have
fCBD,Edd ≈ 0.068
Mtot
109.4M
−1
,
f1,Edd = fCBD,Edd
(1 + q)
1 + η
∼ 0.0034
fCBD,Edd
0.068
1 + q
1.05
21
1 + η
,
f2,Edd = η
f1,Edd
q
1.37
f1,Edd
0.0034
η
20
0.05
q
, (1)
where the subscripts 1 and 2 refer to the primary and the secondary, and Mtot ≡ M1 + M2. We
adopt a standard, radiatively efficient, geometrically thin, optically thick Shakura-Sunyaev (SS)
disk model29
to compute the luminosities produced in the CBD and the circum-secondary disk
(CSD). Although the secondary is accreting at a modestly super-Eddington rate, recent 3D radi-
ation magneto-hydrodynamic simulations of super-Eddington accretion find radiative efficiencies
comparable to the values in standard thin disk models30
. On the other hand, the primary is accret-
ing below the critical rate ˙M1
˙MADAF ≈ 0.027(α/0.3)2 ˙MEdd (with α the viscosity parameter)
for which advection dominates the energy balance31
. We therefore estimate its luminosity from a
radiatively inefficient advection-dominated accretion flow (ADAF)32,33
, rather than a SS disk. This
interpretation is supported by the fact that PG 1302-102 is known to be an extended radio source,
with evidence for a jet and bends in the extended radio structure34
, features that are commonly
associated with sub-Eddington sources35
.
For the radiatively efficient CBD and CSD, the frequency-dependent luminosity is given by
10
11. integrating the local modified blackbody flux over the area of the disk
Lν =2π
Rout
Rin
Fν[Tp(r)] rdr
Fν =π
2
1/2
ν
1 +
1/2
ν
Bν ν =
κabs
ν
κabs
ν + κes
(2)
where Bν is the Planck function, κabs
ν is the frequency-dependent absorption opacity, and κes
is
the electron scattering opacity. We compute the radial disk photosphere temperature profile Tp by
equating the viscous heating rate to the modified blackbody flux
3GM ˙M
8πr3
1 −
rISCO
r
1/2
= ζ(ν, Tp)σT4
p (3)
ζ(ν, Tp) =
15
π4
2
1/2
ν (x)
1 +
1/2
ν (x)
x3
e−x
1 − e−x
dx x ≡
hν
kBTp
.
where σ is the Stefan-Boltzmann constant and kB is Boltzmann’s constant. In solving for the
photosphere temperature we work in the limit that κabs
ν κes
following Appendix A of ref. 36
,
and we adopt ri
ISCO = 6GMi
/c2
and (Rin, Rout) = (2a, 200a), (rs
ISCO, a(q/3)1/3
) for the inner and
outer radii of the CBD and CSD, respectively. Here the superscript i refers to the ith
disk, a is the
binary separation, 6GM is the location of the innermost stable circular orbit for a Schwarzshild
black hole (our results are insensitive to this choise) and a(q/3)1/3
is the secondary’s Hill radius
(which provides an upper limit on the size of the CSD37
).
The optical luminosity of an ADAF is sensitive to the assumed microphysical parameters
and its computation is more complicated than for a thin disk. Here we first compute a reference
thin-disk luminosity LSS for the primary, and multiply it by the ratio of the bolometric luminosity
of an ADAF to an equivalent thin-disk luminosity from ref. 32
,
LADAF
LSS
∼ 0.008
˙M/ ˙MEdd
0.0034
α
0.3
−2
. (4)
For calculating the reference LSS, we adopted parameters consistent with ref. 32
, in particular
= 0.1. Although the above ratio is for the bolometric luminosities, we find that it agrees well
with the factor of 100 difference in the V band shown in Figure 6 of ref. 33
between ADAF and
thin disk spectra with parameters similar to PG 1302-102 (109
M , ˙M = ˙MADAF = 10−1.5 ˙MEdd,
α ≈ 0.3).
Extended Data Fig. 1 shows the thin-disk CBD and CSD spectra for a total Eddington ratio of
fCBD,Edd = 0.07, consistent with the high–mass estimates for PG 1302-102 needed for the beaming
scenario (M = 109.4
M and q = 0.05). The red dot shows the reduced V-band luminosity of an
ADAF onto the primary. The secondary clearly dominates the total V band luminosity, with the
primary contributing less than 1%, and the CBD contributing ∼ 14%. In practice, the contribution
11
12. from the CBD becomes non-negligible only for the smallest binary masses and lowest mass ratios
(reaching 20% for M < 109
M and q < 0.025).
We compute the contributions of each of the three components to the total luminosity, LV
tot =
LV
1 + LV
2 + LV
CBD, and the corresponding total fractional modulation amplitude ∆LV
tot/LV
tot =
(∆LV
1 + ∆LV
2 )/LV
tot, for each value of the total mass M and mass ratio q. The primary is assumed
to be Doppler-modulated with a line-of sight velocity v1 = −qv2 while the emission from the CBD
is assumed constant over time (∆LV
CBD = 0). Extended Data Fig. 2 shows regions in the (M, q, i)
parameter space where the total luminosity variation due to relativistic beaming exceeds 14%. This
recreates Fig. 1 of the main text, but using the luminosity contributions computed self-consistently
in the above model, rather than assuming a constant value of f2. Because the secondary is found to
be dominant, the relativistic beaming scenario is consistent with a wide range of binary parameters.
Model fitting to the PG 1302-102 optical light curve. We fit models to the observed light curve
of PG 1302-102 by maximising the Bayesian likelihood L ∝ det|CovD
Covph
|−1/2
exp(−χ2
/2),
where
χ2
≡ YT
(Cov)−1
Y, (5)
and Y ≡ O − M is the difference vector between the mean flux predicted in a model and the
observed flux at each observation time ti. Here Cov is the covariance matrix of flux uncertain-
ties, allowing for correlations between fluxes measured at different ti. We include two types of
uncertainties: (1) random (uncorrelated) measurement errors,
Covph
ij =
σ2
i i = j
0 i = j
(6)
where σ2
i is the variance in the photometric measurement for the ith
data point (as reported in
ref. 6
), and (2) correlated noise due to intrinsic quasar variability, with covariance between the ith
and jth
data points,
CovD
ij = σ2
Dexp
−|ti − tj|
(1 + z)τD
. (7)
The parameters σD and τD determine the amplitude and rest–frame coherence time of correlated
noise described by the damped random walk (DRW) model24
, and the factor of (1 + z) converts
τD to the observer’s frame where the ti are measured. These parameters enter the normalisation of
the Bayesian likelihood, and this normalisation must therefore be included when maximising the
likelihood over these parameters38
. The covariance matrix for the total noise is given by Cov =
CovD
+ Covph
. We assume both types of noise are Gaussian, which provides a good description
of observed quasar variability39
.
We then fit the following four different types of models to the data:
• Relativistic beaming model with 5+2=7 model parameters: eccentricity, argument of peri-
center, amplitude, phase and orbital period, plus the two noise parameters σD and τD.
12
13. • Accretion rate model with 3+2=5 model parameters: amplitude, phase and period, plus the
two noise parameters. This model assumes that PG 1302-102’s light-curve tracks the mass
accretion rates predicted in hydrodynamical simulations. For near-equal mass binaries, sev-
eral studies have found that the mass accretion rates fluctuate periodically, but they resemble
a series of sharp bursts, unlike the smoother, sinusoid-like shape of PG 1302-102’s light-
curve. To our knowledge, only three studies to date have simulated unequal-mass (q ≤ 0.1)
SMBH binaries11,13,15
. The accretion rates for these binaries are less bursty; among all of
the cases in these three studies, the q = 0.075 and q = 0.1 binaries in ref 11
resemble
PG 1302-102’s light-curve most closely (shown in Extended Data Fig. 3). Here we adopt
the published accretion curve for q = 0.1, and perform a fit to PG 1302-102 by allowing an
arbitrary linear scaling in time and amplitude, as well as a shift in phase; this gives us the
three free parameters for this model. (We find that the q = 0.075 case provides a worse fit.)
• Sinusoid model with 3+2 parameters: amplitude, phase and period, plus the two noise pa-
rameters. This model is equivalent, to first order in v/c, to the beaming model restricted to a
circular binary orbit.
• Constant luminosity model with 2 parameters: for reference only – to quantify how poor the
fit is with only an amplitude plus the two noise parameters.
In each of these models above, we have fixed the mean flux to equal its value inferred from
the optical data. We have found that allowing the mean to be an additional free parameter did
not change our results. The highest maximum likelihood is found for the beaming model, with
best-fit values of (P = [1996]+29
−35 days, K = [0.065]+0.007
−0.006 c, e = 0.09+0.07
−0.06, cos ω = [−0.65]+1.2
−0.06,
t0 = [718]+422
−34 days), where the reference point t0 is measured from MJD−49100. Uncertainties
are computed with the emcee code40
, which implements a Markov Chain Monte Carlo algorithm,
and which we use to sample the 7D posterior probability of the model given the G15 data. In
practice, we employ 28 individual chains to sample the posterior for 1024 steps each. Throwing
away the first 600 steps (‘burning in’), we run for 424 steps and for each parameter, we quote best-
fit values corresponding to the maximum posterior probability, with errors given by the 85th
and
15th
percentile values (marginalized over the other six parameters) . The best-fit noise parameters
are found to be (σD, τD) = (0.049+0.016
−0.001 mag, 37.6+35.2
−1.5 days). The best-fit model has a reduced
χ2
/(N − 1 − 7) ≈ 2.1, where N = 245 is the number of data points.
To assess which of the above model is favoured by the data, we use the Bayesian Information
Criterion (BIC), a standard method for comparing different models, penalising models with a larger
number of free parameters41
. Specifically, BIC= −2 ln L+k ln N, where the first term is evaluated
using the best-fit parameters in each of the models and where k is the number of model parameters.
We find the following differences ∆BIC between pairs of models:
BICAcc − BICBeam = 4.0 (Beaming model preferred over accretion model)
BICAcc − BICSin = 14.9 (Sin model strongly preferred over accretion model)
BICSin − BICBeam = −10.9 (Sin model strongly preferred over eccentric beaming model)
BICConst − BICBeam = 11.5 (Beaming model strongly preferred over pure noise)
BICConst − BICSin = 22.4 (Sin model strongly preferred over pure noise).
13
14. We conclude that a sinusoid, or equivalently the beaming model restriced to a circular binary,
is the preferred model. In particular, this model is very strongly favoured over the best–fit accretion
models (see Extended Data Fig. 3), with ∆BIC > 14.9. For the assumed Gaussian distributions,
this corresponds to an approximate likelihood ratio of exp(−14.9/2) ≈ 5.7 × 10−4
. Although
our best–fit beaming model has a small non-zero eccentricity, the 7-parameter eccentric model is
disfavoured (by ∆BIC = 11.5) over the 5-parameter circular case.
We have conservatively allowed the amplitude of accretion rate fluctuations to be a free
parameter in the accretion models, but we note that the accretion rate variability measured in
hydrodynamic simulations exhibits large (order unity) deviations from the mean, even for 0.05 <
q < 0.1 binaries 11,13,15
. In the accretion rate models, an additional physical mechanism needs to
be invoked to damp the fluctuations to the smaller ∼ 14% amplitude seen in PG 1302-102 (such as
a more significant contribution from the CBD and/or the primary).
Disk Precession. The lowest BIC model, with a steady accretion rate and a relativistic boost from
a circular orbit, has a reduced χ2
= 2.1, indicating that the relativistic boost model with intrin-
sic noise does not fully describe the observed light-curve. The residuals could be explained by
a lower-amplitude periodic modulation in the mass accretion rate, which is expected to have a
non-sinusoidal shape (i.e. with sharper peaks and broader troughs, as mentioned above13
). Alter-
natively, the minidisks, which we have implicitly assumed to be co-planar with the binary orbit,
could instead have a significant tilt12
.
A circum-secondary minidisk that is tilted with respect to the binary’s orbital plane will
precess around the binary angular momentum vector, causing additional photometric variations due
to the changing projected area of the disk on the sky. The precession timescale can be estimated
from the total angular momentum of the secondary disk and the torque exerted on it by the primary
black hole. The ratio of the precession period to the binary’s orbital period is 42
,
Pprec
Porb
= −
8
√
3
√
1 + q
cos δ
, (8)
where we have chosen the outer edge of the minidisk to coincide with the secondary’s Hill sphere
RH = (q/3)1/3
a, for binary semi-major axis a. This choice gives the largest secondary disk and the
shortest precession rates. The angle δ between the disk angular momentum vector and the binary
angular momentum vector can range from −π/2 to π/2. For small binary mass ratios, consistent
with the relativistic beaming scenario, the precession can be as short as 4.8Porb, causing variations
on a timescale spanning the current observations of PG 1302-102. The precession timescale would
be longer (> 20Porb) for a smaller secondary disk tidally truncated at 0.27q0.3
a 43
, and with a more
inclined (45◦
) disk.
Archival UV data. FUV (0.14-0.175µm) and NUV (0.19-0.27µm) spectra of PG 1302-102 were
obtained by the Hubble Space Telescope (HST) and the Galaxy Evolution Explorer (GALEX)
since 1992. HST/Faint Object Spectrograph (FOS) NUV spectra were obtained on July 17, 1992
(pre-COSTAR)44
. HST/Space Telescope Imaging Spectrograph (STIS) FUV spectra were obtained
on August 21, 200145
. GALEX FUV and NUV spectra were obtained on March 8, 2008 and April
14
15. 6, 2009 and HST/Cosmic Origins Spectrograph (COS) FUV spectra were obtained on January 28,
2011. All data are publicly available through the Mikulski Archive for Space Telescopes (MAST)
at archive.stsci.edu. All measurements have been spectrophotometrically calibrated, and binned or
smoothed to 1-3 ˚A resolution. The spectra (shown in Fig. 2 in the main text) have errors per bin
typically less than 2% and published absolute photometric accuracies are better than 5%.
From each spectrum, average flux measurements (shown in Fig. 2 in the main text) were
obtained in one or both of two discrete bands: FUV continuum from 0.145-0.1525µm for FUV
(a range chosen to avoid the Lyα line) and NUV continuum from 0.20-0.26µm. For the GALEX
NUV photometric data (also used in Fig. 2) we adopted a small correction (0.005 mag) for the
transformation from the GALEX NUV to our NUV continuum band. GALEX FUV photometric
data were not used because of the significant contribution from redshifted Lyα. Note that the broad
lines in the UV spectra (in Fig. 3) do not show a large ∆λ = (v/c)λ ≈ 140 ˚A Doppler shift. This is
unsurprising, since the broad line widths (2,500-4,500 km s−1
) are much smaller than the inferred
relativistic line-of-sight velocities, and are expected to be produced by gas at larger radii, unrelated
to the rapidly orbiting minidisks producing the featureless thermal continuum emission22
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16
17. Extended Data Figure 1 | Model spectrum of PG 1302-102. Circumbinary (dashed blue) and
circumsecondary (solid black) disk spectra for a total binary mass of 109.4
, binary mass ratio q =
0.05, and ratio of accretion rates ˙M2/ ˙M1 = 20. A vertical dashed line marks the center of the
V-band and the approximate flux from an advection–dominated accretion flow (ADAF) is shown
as a red dot for the V-band contribution of the primary. The spectrum for a radiatively efficient,
thin disk around the primary is shown by the thin red dashed curve for reference.
17
18. q = 0.05
q = 0.025
q = 0.1
q = 0.2
Extended Data Figure 2 | Parameter combinations for which the combined V-band luminos-
ity of the three–component system varies by the required 0.14 mag. M is the binary mass, q
is the mass ratio, and i is the orbital inclination angle. This figure is analogous to Fig. 1, except
instead of adopting a fractional luminosity contribution f2 by the secondary, the luminosities of
each of the three components are computed from a model: the primary’s luminosity is assumed to
arise from an ADAF, while the secondary’s luminosity is generated by a modestly super-Eddington
thin disk. Emission from the circumbinary disk is also from a thin disk, and is negligible except
for binaries with the lowest mass ratio q <∼0.01 (see text).
18
19. Extended Data Figure 3 | Model fits to PG 1302-102’s optical light curve. Best–fitting curves
assuming relativistic boost from a circular binary (solid black curves), a pure sinusoid (red dotted
curves) and accretion rate variability adopted from hydrodynamical simulations11
(blue dashed
curves) for a q = 0.075 (a) and a q = 0.1 (b) mass–ratio binary. The grey points with 1σ errors
bars show the data for PG 1302-1026
.
19