Planets orbiting close to hot stars experience intense extreme-ultraviolet
radiation, potentially leading to atmosphere evaporation and to thermal
dissociation of molecules. However, this extreme regime remains mainly
unexplored due to observational challenges. Only a single known ultra-hot
giant planet, KELT-9b, receives enough ultraviolet radiation for molecular
dissociation, with a day-side temperature of ~4,600 K. An alternative
approach uses irradiated brown dwarfs as hot-Jupiter analogues. With
atmospheres and radii similar to those of giant planets, brown dwarfs
orbiting close to hot Earth-sized white dwarf stars can be directly detected
above the glare of the star. Here we report observations revealing
an extremely irradiated low-mass companion to the hot white dwarf
WD 0032–317. Our analysis indicates a day-side temperature of ~8,000 K,
and a day-to-night temperature difference of ~6,000 K. The amount of
extreme-ultraviolet radiation (with wavelengths 100–912 Å) received by
WD 0032–317B is equivalent to that received by planets orbiting close to stars
as hot as late B-type stars, and about 5,600 times higher than that of KELT-9b.
With a mass of ~75–88 Jupiter masses, this near-hydrogen-burning-limit
object is potentially one of the most massive brown dwarfs known.
An irradiated-Jupiter analogue hotter than the SunSérgio Sacani
Planets orbiting close to hot stars experience intense extreme-ultraviolet radiation, potentially leading to
atmosphere evaporation and to thermal dissociation of molecules. However, this extreme regime remains
mainly unexplored due to observational challenges. Only a single known ultra-hot giant planet, KELT-9b,
receives enough ultraviolet radiation for molecular dissociation, with a day-side temperature of ≈ 4, 600 K.
An alternative approach uses irradiated brown dwarfs as hot-Jupiter analogues. With atmospheres and radii
similar to those of giant planets, brown dwarfs orbiting close to hot Earth-sized white-dwarf stars can be
directly detected above the glare of the star. Here we report observations revealing an extremely irradiated
low-mass companion to the hot white dwarf WD0032−317. Our analysis indicates a day-side temperature
of ≈ 8, 000 K, and a day-to-night temperature difference of ≈ 6, 000 K. The amount of extreme-ultraviolet
radiation (with wavelengths 100−912 ˚A) received byWD0032−317B is equivalent to that received by planets
orbiting close to stars as hot as a late B-type stars, and about 5, 600 times higher than that of KELT-9b. With
a mass of ≈ 75 − 88 Jupiter masses, this near-hydrogen-burning-limit object is potentially one of the most
massive brown dwarfs known.
An earth sized_planet_with_an_earth_sized_densitySérgio Sacani
1) Researchers observed the exoplanet Kepler-78b using the HARPS-N spectrograph to measure its mass.
2) They measured Kepler-78b's mass to be 1.86 Earth masses, giving it a density similar to Earth, implying a rocky composition of iron and rock.
3) The small size of Kepler-78b makes it the smallest exoplanet yet measured for both mass and radius, establishing that Earth-sized planets can be terrestrial.
A dust obscured_massive_maximum_starburst_galaxy_at_a_redshift_634Sérgio Sacani
This document summarizes the discovery of a massive, intensely star-forming galaxy located at a redshift of 6.34, approximately 880 million years after the Big Bang. Observations revealed a suite of molecular and atomic emission and absorption lines that unambiguously determined the galaxy's redshift. Analysis shows the galaxy contains over 100 billion solar masses of chemically evolved interstellar medium, constituting at least 40% of its baryonic mass. It is forming new stars at a rate over 2,000 times that of the Milky Way, making it a "maximum starburst" galaxy. Despite an overall decline in cosmic star formation at the highest redshifts, this discovery shows that environments capable of hosting the most massive starbursts existed very early
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
This document reports the discovery of the central star of the planetary nebula IC 4663, which exhibits spectral properties that mimic a nitrogen-rich Wolf-Rayet star of spectral type [WN3]. This makes it the first unambiguous case of a planetary nebula central star taking on the properties of a Wolf-Rayet star. The central star is dominated by broad helium and nitrogen emission lines. The surrounding nebula is definitively a planetary nebula based on its morphology and chemical abundances. The discovery provides evidence for an alternative evolutionary pathway for some hydrogen-deficient, helium-rich post-asymptotic giant branch stars.
Three new circumbinary planets have been discovered orbiting binary star systems, rather than single stars. This establishes a new class of planets and shows that circumbinary planets are not rare, with an estimated frequency of at least 1% for short-period binary systems, implying millions exist in the Milky Way. While the three discovered planets are too hot or cold to support life, circumbinary planets could potentially be habitable.
Multimessenger observations of a flaring blazar coincident with high-energy n...Sérgio Sacani
Neutrinos are tracers of
cosmic-ray acceleration: electrically neutral
and traveling at nearly the speed of light, they
can escape the densest environments and may
be traced back to their source of origin. Highenergy
neutrinos are expected to be produced
in blazars: intense extragalactic radio, optical,
x-ray, and,in some cases, g-ray sources
characterized by relativistic jets of
plasma pointing close to our line of
sight. Blazars are among the most
powerful objects in the Universe and
are widely speculated to be sources
of high-energy cosmic rays. These cosmic
rays generate high-energy neutrinos
and g-rays, which are produced
when the cosmic rays accelerated in
the jet interact with nearby gas or
photons. On 22 September 2017, the
cubic-kilometer IceCube Neutrino
Observatory detected a ~290-TeV
neutrino from a direction consistent
with the flaring g-ray blazar TXS
0506+056. We report the details of
this observation and the results of a
multiwavelength follow-up campaign
An irradiated-Jupiter analogue hotter than the SunSérgio Sacani
Planets orbiting close to hot stars experience intense extreme-ultraviolet radiation, potentially leading to
atmosphere evaporation and to thermal dissociation of molecules. However, this extreme regime remains
mainly unexplored due to observational challenges. Only a single known ultra-hot giant planet, KELT-9b,
receives enough ultraviolet radiation for molecular dissociation, with a day-side temperature of ≈ 4, 600 K.
An alternative approach uses irradiated brown dwarfs as hot-Jupiter analogues. With atmospheres and radii
similar to those of giant planets, brown dwarfs orbiting close to hot Earth-sized white-dwarf stars can be
directly detected above the glare of the star. Here we report observations revealing an extremely irradiated
low-mass companion to the hot white dwarf WD0032−317. Our analysis indicates a day-side temperature
of ≈ 8, 000 K, and a day-to-night temperature difference of ≈ 6, 000 K. The amount of extreme-ultraviolet
radiation (with wavelengths 100−912 ˚A) received byWD0032−317B is equivalent to that received by planets
orbiting close to stars as hot as a late B-type stars, and about 5, 600 times higher than that of KELT-9b. With
a mass of ≈ 75 − 88 Jupiter masses, this near-hydrogen-burning-limit object is potentially one of the most
massive brown dwarfs known.
An earth sized_planet_with_an_earth_sized_densitySérgio Sacani
1) Researchers observed the exoplanet Kepler-78b using the HARPS-N spectrograph to measure its mass.
2) They measured Kepler-78b's mass to be 1.86 Earth masses, giving it a density similar to Earth, implying a rocky composition of iron and rock.
3) The small size of Kepler-78b makes it the smallest exoplanet yet measured for both mass and radius, establishing that Earth-sized planets can be terrestrial.
A dust obscured_massive_maximum_starburst_galaxy_at_a_redshift_634Sérgio Sacani
This document summarizes the discovery of a massive, intensely star-forming galaxy located at a redshift of 6.34, approximately 880 million years after the Big Bang. Observations revealed a suite of molecular and atomic emission and absorption lines that unambiguously determined the galaxy's redshift. Analysis shows the galaxy contains over 100 billion solar masses of chemically evolved interstellar medium, constituting at least 40% of its baryonic mass. It is forming new stars at a rate over 2,000 times that of the Milky Way, making it a "maximum starburst" galaxy. Despite an overall decline in cosmic star formation at the highest redshifts, this discovery shows that environments capable of hosting the most massive starbursts existed very early
1. VFTS 682 is a very massive star located 29 pc in projection from the young massive cluster R136 in the Tarantula Nebula of the LMC.
2. Spectral modeling finds it has an unusually high luminosity of log(L/L) = 6.5, corresponding to a present-day mass of ~150 solar masses.
3. Its isolation and mass pose the question of whether it formed in situ, which would profoundly impact theories of massive star formation, or if it was ejected from R136, making it the most massive runaway star known.
This document reports the discovery of the central star of the planetary nebula IC 4663, which exhibits spectral properties that mimic a nitrogen-rich Wolf-Rayet star of spectral type [WN3]. This makes it the first unambiguous case of a planetary nebula central star taking on the properties of a Wolf-Rayet star. The central star is dominated by broad helium and nitrogen emission lines. The surrounding nebula is definitively a planetary nebula based on its morphology and chemical abundances. The discovery provides evidence for an alternative evolutionary pathway for some hydrogen-deficient, helium-rich post-asymptotic giant branch stars.
Three new circumbinary planets have been discovered orbiting binary star systems, rather than single stars. This establishes a new class of planets and shows that circumbinary planets are not rare, with an estimated frequency of at least 1% for short-period binary systems, implying millions exist in the Milky Way. While the three discovered planets are too hot or cold to support life, circumbinary planets could potentially be habitable.
Multimessenger observations of a flaring blazar coincident with high-energy n...Sérgio Sacani
Neutrinos are tracers of
cosmic-ray acceleration: electrically neutral
and traveling at nearly the speed of light, they
can escape the densest environments and may
be traced back to their source of origin. Highenergy
neutrinos are expected to be produced
in blazars: intense extragalactic radio, optical,
x-ray, and,in some cases, g-ray sources
characterized by relativistic jets of
plasma pointing close to our line of
sight. Blazars are among the most
powerful objects in the Universe and
are widely speculated to be sources
of high-energy cosmic rays. These cosmic
rays generate high-energy neutrinos
and g-rays, which are produced
when the cosmic rays accelerated in
the jet interact with nearby gas or
photons. On 22 September 2017, the
cubic-kilometer IceCube Neutrino
Observatory detected a ~290-TeV
neutrino from a direction consistent
with the flaring g-ray blazar TXS
0506+056. We report the details of
this observation and the results of a
multiwavelength follow-up campaign
No xrays from_wasp18_implications_for_its_age_activity_and_influenceSérgio Sacani
1) An 87 ks Chandra observation was performed of the star WASP-18, which hosts a very close-in hot Jupiter planet orbiting within 20 hours.
2) WASP-18 was not detected in X-rays down to a luminosity limit of 4 x 10^26 erg/s, over two orders of magnitude lower than expected for a star of its estimated age of 600 Myr.
3) This unusually low activity level for a star of WASP-18's age and mass suggests that the massive planet may play a role in disrupting the stellar magnetic dynamo generated within its thin convective layers through star-planet interaction.
WASP-18: NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act De...GOASA
This document summarizes a study observing the star WASP-18 and its hot Jupiter planet using the Chandra X-ray Observatory. The star was not detected in X-rays down to a luminosity limit much lower than expected for its estimated age of 600 million years. This suggests unusual lack of magnetic activity, which the authors argue may be due to disruption of the stellar dynamo by the massive planet in its close orbit. Over 200 other X-ray sources were also detected in the Chandra image and are listed. The non-detection of X-rays from WASP-18 has implications for models of star-planet interaction and the evolutionary stage of this system.
Monthly quasi-periodic eruptions from repeated stellar disruption by a massiv...Sérgio Sacani
In recent years, searches of archival X-ray data have revealed galaxies
exhibiting nuclear quasi-periodic eruptions with periods of several hours.
These are reminiscent of the tidal disruption of a star by a supermassive
black hole. The repeated, partial stripping of a white dwarf in an eccentric
orbit around an ~105 M⊙ black hole provides an attractive model. A separate
class of periodic nuclear transients, with much longer timescales, have
recently been discovered optically and may arise from the partial stripping
of a main-sequence star by an ~107 M⊙ black hole. No clear connection
between these classes has been made. We present the discovery of an X-ray
nuclear transient that shows quasi-periodic outbursts with a period of
weeks. We discuss possible origins for the emission and propose that this
system bridges the two existing classes outlined above. This discovery was
made possible by the rapid identifcation, dissemination and follow-up
of an X-ray transient found by the new live Swift-XRT transient detector,
demonstrating the importance of low-latency, sensitive searches for
X-ray transients.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
50 Years of the Astronomy Centre at the University of SussexPeter Coles
This summarizes about 50 research papers and other notable events, approximately one for each year of existence of the Astronomy Centre at the University of Sussex (1966-2016). Shown at a special event on 15th October 2016. to mark the 50th Anniversary
Detection of brown dwarf like objects in the core of ngc3603Sérgio Sacani
This document describes observations of the massive galactic cluster NGC 3603 using the Wide Field Camera 3 on the Hubble Space Telescope. Near-infrared data was obtained using narrow and medium band filters spanning the J and H bands, which are sensitive to the 1.3-1.5μm H2O molecular absorption band unique to brown dwarfs. Nine objects were identified having effective temperatures between 1700-2200K, typical of brown dwarfs, located strongly clustered towards the luminous core of NGC 3603. However, if located at the distance of the cluster, these objects would be too luminous to be normal brown dwarfs. The authors explore the possibility that these objects could represent a new class of stars having
This document summarizes research on determining temperatures, luminosities, and masses of the coldest known brown dwarfs. The key findings are:
1) Precise distances were measured for a sample of late-T and Y dwarfs using Spitzer Space Telescope astrometry, allowing accurate calculation of absolute fluxes, luminosities, and temperatures.
2) Y0 dwarfs were found to have temperatures of 400-450 K, significantly warmer than previous estimates, and masses of 5-20 times Jupiter's mass.
3) While having similar temperatures, Y dwarfs showed diverse spectral energy distributions, suggesting temperature alone does not determine spectra. Physical properties like gravity, clouds and chemistry also influence spectra.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the bolometric luminosity. An obscured AGN combined with starburst and
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z=2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission of WISE 1814+3412 and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the total luminosity. An obscured
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
This document presents a sample of 20 extremely luminous galaxies discovered by the Wide-field Infrared Survey Explorer (WISE). Five of these galaxies have infrared luminosities exceeding 1014 solar luminosities, the highest infrared luminosity threshold yet observed. They were selected using criteria requiring weak or no detection in the first two WISE bands but strong detections in the third and fourth bands. Spectral energy distribution modeling suggests their high luminosities are powered by obscured active galactic nuclei with hot dust temperatures around 450 Kelvin. The existence of such luminous galaxies at redshifts above 3 provides constraints on the early growth of supermassive black holes through rapid accretion.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Bright radio emission_from_an_ultraluminous_stellar_mass_microquasar_in_m31Sérgio Sacani
1) A new ultraluminous X-ray source (ULX) was detected in the galaxy M31 with a peak X-ray luminosity exceeding 10^39 erg s^-1.
2) Radio observations found highly variable radio emission on timescales of minutes to days, indicating an extremely compact emission region.
3) The X-ray and radio properties of this source are consistent with stellar-mass black hole accretion near or above the Eddington limit, powered by a relativistic jet as seen in Galactic microquasars.
A continuum from_clear_to_cloudy_hot_jupiter_exoplanets_without_primordial_wa...Sérgio Sacani
Uma pesquisa de 10 exoplanetas quentes, do tamanho de Júpiter, conduzida com os telescópios Spitzer e Hubble da NASA levou uma equipe de astrônomos a resolverem um mistério que já durava algum tempo – por que alguns desses mundos têm menos água do que o esperado? A descoberta, oferece novas ideias sobre uma vasta coleção de atmosferas planetárias na nossa galáxia e sobre como os planetas são formados.
Dos quase 2000 planetas confirmados orbitando outras estrelas, um subconjunto deles são planetas gasosos com características similares ao planeta Júpiter, mas, como suas órbitas são muito próximas de suas estrelas, eles são terrivelmente quentes.
A proximidade desses exoplanetas das suas estrelas, faz com que seja difícil observá-los. Devido a essa dificuldade, o Hubble só conseguiu explorar poucos desses exoplanetas, chamados de Júpiteres Quentes, no passado. Esses estudos iniciais descobriram que alguns planetas possuem menos água do que era previsto pelos modelos atmosféricos.
Uma equipe internacional de astrônomos tem atacado o problema fazendo o maior catálogo espectroscópico de atmosferas de exoplanetas até o momento. Todos os planetas no catálogo seguem órbitas orientadas de modo que o planeta passa em frente da estrela quando visto da Terra. Devido a esse trânsito, parte da luz da estrela viaja pela atmosfera externa do exoplaneta. “A atmosfera deixa sua impressão digital única na luz da estrela, que nós podemos estudar, quando ela chega até nós”, explicou a coautora Hannah Wakeford, do Goddard Space Flight Center da NASA , em Greenbelt, Maryland.
NGC 680 and NGC 5557 are early-type galaxies that were observed with deep optical imaging to study their outer morphologies. NGC 680 exhibits extended plumes and tails that appear connected to HI gas, as well as arcs and shells. NGC 5557 has a gigantic 160 kpc long narrow tail containing three star-forming objects. The features suggest that each galaxy underwent a major wet merger over 1-2 Gyr ago, with NGC 5557's merger dominating its formation history and making it a slow rotator, while NGC 680 rotates faster.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
This document provides an overview of the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune). It discusses the composition and structure of their atmospheres based on equilibrium cloud condensation models. The atmospheres contain temperature minima at the tropopause, above which temperatures increase due to absorption of sunlight, and below which temperatures increase with depth due to convection. While early models predicted ammonia and water cloud decks, spacecraft observations have since directly observed ammonia clouds on Jupiter but found they are short-lived, suggesting other cloud composition processes.
This document summarizes research that used gravitational lensing to study dusty starburst galaxies in the early universe. Key findings include:
- ALMA observations of 26 extremely bright millimeter-selected galaxies found spectral lines confirming redshifts in 23, with at least 10 at z > 4.
- High-resolution ALMA imaging showed the galaxies are strongly lensed by foreground galaxies, with magnifications of 4-22x.
- Correcting for magnification, the starburst galaxies have luminosities over 1012 solar luminosities, implying star formation rates over 500 solar masses per year.
- The findings more than double the number of spectroscopically confirmed ultra-luminous galaxies known at z
Radio imaging obserations_of_psr_j1023_0038_in_an_lmxb_stateSérgio Sacani
Uma estrela super densa formada depois da explosão de uma supernova está expelindo poderosos jatos de material no espaço, sugerem pesquisas recentes.
Num estudo publicado no dia 6 de Agosto de 2015, uma equipe de cientistas na Austrália e na Holanda descobriram poderosos jatos sendo expelidos de uma sistema estelar duplo conhecido como PSR J1023+0038.
Pensava-se anteriormente que os únicos objetos no universo capazes de formar jatos poderosos eram os buracos negros.
O sistema PSR J1023+0038 contém uma estrela extremamente densa que os astrônomos chamam de estrela de nêutrons, numa órbita próxima com uma estrela normal.
Ela foi identificada primeiro como uma estrela de nêutrons em 2009, mas foi somente quando a equipe de pesquisa observou a estrela com o rádio telescópio Very Large Array nos EUA em 2013 e 2014 que eles perceberam que a estrela estava produzindo jatos mais fortes do que se esperava.
Os astrônomos James Miller-Jones, do International Centre for Radio Astronomy Research (ICRAR), disse que as estrelas de nêutrons podem ser pensadas como cadáveres estelares.
“Elas são formadas quando uma estrela massiva esgota todo o seu combustível e vira uma supernova, e as partes centrais da estrela colapsam sobre sua própria gravidade”, disse ele.
“Essas coisas tem normalmente entre uma vez e meia a massa do Sol e somente entre 10 a 15 km de diâmetro, de modo que são extremamente densas”.
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
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No xrays from_wasp18_implications_for_its_age_activity_and_influenceSérgio Sacani
1) An 87 ks Chandra observation was performed of the star WASP-18, which hosts a very close-in hot Jupiter planet orbiting within 20 hours.
2) WASP-18 was not detected in X-rays down to a luminosity limit of 4 x 10^26 erg/s, over two orders of magnitude lower than expected for a star of its estimated age of 600 Myr.
3) This unusually low activity level for a star of WASP-18's age and mass suggests that the massive planet may play a role in disrupting the stellar magnetic dynamo generated within its thin convective layers through star-planet interaction.
WASP-18: NASA's Chandra X-ray Observatory Finds Planet That Makes Star Act De...GOASA
This document summarizes a study observing the star WASP-18 and its hot Jupiter planet using the Chandra X-ray Observatory. The star was not detected in X-rays down to a luminosity limit much lower than expected for its estimated age of 600 million years. This suggests unusual lack of magnetic activity, which the authors argue may be due to disruption of the stellar dynamo by the massive planet in its close orbit. Over 200 other X-ray sources were also detected in the Chandra image and are listed. The non-detection of X-rays from WASP-18 has implications for models of star-planet interaction and the evolutionary stage of this system.
Monthly quasi-periodic eruptions from repeated stellar disruption by a massiv...Sérgio Sacani
In recent years, searches of archival X-ray data have revealed galaxies
exhibiting nuclear quasi-periodic eruptions with periods of several hours.
These are reminiscent of the tidal disruption of a star by a supermassive
black hole. The repeated, partial stripping of a white dwarf in an eccentric
orbit around an ~105 M⊙ black hole provides an attractive model. A separate
class of periodic nuclear transients, with much longer timescales, have
recently been discovered optically and may arise from the partial stripping
of a main-sequence star by an ~107 M⊙ black hole. No clear connection
between these classes has been made. We present the discovery of an X-ray
nuclear transient that shows quasi-periodic outbursts with a period of
weeks. We discuss possible origins for the emission and propose that this
system bridges the two existing classes outlined above. This discovery was
made possible by the rapid identifcation, dissemination and follow-up
of an X-ray transient found by the new live Swift-XRT transient detector,
demonstrating the importance of low-latency, sensitive searches for
X-ray transients.
This document summarizes the results of a deep near-infrared survey of the Carina Nebula complex using the HAWK-I instrument on the VLT. The survey imaged an area of 0.36 square degrees down to magnitudes of J=23, H=22, and Ks=21, detecting over 600,000 infrared sources. Color-magnitude diagrams of the sources were analyzed to determine properties of the low-mass stellar population such as ages and masses. The survey found that about 3200 sources have masses above 1 solar mass, consistent with expectations from the initial mass function. It also found that about half of the young stars in Carina are in a widely distributed, non-clustered configuration. Six
50 Years of the Astronomy Centre at the University of SussexPeter Coles
This summarizes about 50 research papers and other notable events, approximately one for each year of existence of the Astronomy Centre at the University of Sussex (1966-2016). Shown at a special event on 15th October 2016. to mark the 50th Anniversary
Detection of brown dwarf like objects in the core of ngc3603Sérgio Sacani
This document describes observations of the massive galactic cluster NGC 3603 using the Wide Field Camera 3 on the Hubble Space Telescope. Near-infrared data was obtained using narrow and medium band filters spanning the J and H bands, which are sensitive to the 1.3-1.5μm H2O molecular absorption band unique to brown dwarfs. Nine objects were identified having effective temperatures between 1700-2200K, typical of brown dwarfs, located strongly clustered towards the luminous core of NGC 3603. However, if located at the distance of the cluster, these objects would be too luminous to be normal brown dwarfs. The authors explore the possibility that these objects could represent a new class of stars having
This document summarizes research on determining temperatures, luminosities, and masses of the coldest known brown dwarfs. The key findings are:
1) Precise distances were measured for a sample of late-T and Y dwarfs using Spitzer Space Telescope astrometry, allowing accurate calculation of absolute fluxes, luminosities, and temperatures.
2) Y0 dwarfs were found to have temperatures of 400-450 K, significantly warmer than previous estimates, and masses of 5-20 times Jupiter's mass.
3) While having similar temperatures, Y dwarfs showed diverse spectral energy distributions, suggesting temperature alone does not determine spectra. Physical properties like gravity, clouds and chemistry also influence spectra.
The extremely high albedo of LTT 9779 b revealed by CHEOPSSérgio Sacani
Optical secondary eclipse measurements of small planets can provide a wealth of information about the reflective properties
of these worlds, but the measurements are particularly challenging to attain because of their relatively shallow depth. If such signals
can be detected and modeled, however, they can provide planetary albedos, thermal characteristics, and information on absorbers in
the upper atmosphere.
Aims. We aim to detect and characterize the optical secondary eclipse of the planet LTT 9779 b using the CHaracterising ExOPlanet
Satellite (CHEOPS) to measure the planetary albedo and search for the signature of atmospheric condensates.
Methods. We observed ten secondary eclipses of the planet with CHEOPS. We carefully analyzed and detrended the light curves using
three independent methods to perform the final astrophysical detrending and eclipse model fitting of the individual and combined light
curves.
Results. Each of our analysis methods yielded statistically similar results, providing a robust detection of the eclipse of LTT 9779 b
with a depth of 115±24 ppm. This surprisingly large depth provides a geometric albedo for the planet of 0.80+0.10
−0.17, consistent with
estimates of radiative-convective models. This value is similar to that of Venus in our own Solar System. When combining the eclipse
from CHEOPS with the measurements from TESS and Spitzer, our global climate models indicate that LTT 9779 b likely has a super
metal-rich atmosphere, with a lower limit of 400× solar being found, and the presence of silicate clouds. The observations also reveal
hints of optical eclipse depth variability, but these have yet to be confirmed.
Conclusions. The results found here in the optical when combined with those in the near-infrared provide the first steps toward
understanding the atmospheric structure and physical processes of ultrahot Neptune worlds that inhabit the Neptune desert.
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the bolometric luminosity. An obscured AGN combined with starburst and
The first hyper_luminous_infrared_galaxy_discovered_by_wiseSérgio Sacani
This document summarizes the discovery of WISE J181417.29+341224.9 (WISE 1814+3412), the first hyper-luminous infrared galaxy (LIR > 1013 L⊙) discovered by the Wide-field Infrared Survey Explorer (WISE). Follow-up images of WISE 1814+3412 revealed four nearby sources - a QSO, two Lyman Break Galaxies at z=2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission of WISE 1814+3412 and has a star formation rate of ~300M⊙ yr−1, accounting for <10% of the total luminosity. An obscured
The most luminous_galaxies_discovered_by_wiseSérgio Sacani
This document presents a sample of 20 extremely luminous galaxies discovered by the Wide-field Infrared Survey Explorer (WISE). Five of these galaxies have infrared luminosities exceeding 1014 solar luminosities, the highest infrared luminosity threshold yet observed. They were selected using criteria requiring weak or no detection in the first two WISE bands but strong detections in the third and fourth bands. Spectral energy distribution modeling suggests their high luminosities are powered by obscured active galactic nuclei with hot dust temperatures around 450 Kelvin. The existence of such luminous galaxies at redshifts above 3 provides constraints on the early growth of supermassive black holes through rapid accretion.
Spirals and clumps in V960 Mon: signs of planet formation via gravitational i...Sérgio Sacani
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due
to the scarcity of observations of fragmented protoplanetary disks around young stars and low occurrence rate
of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation
of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered
light with several spiral arms. This finding motivated a re-analysis of archival ALMA 1.3 mm data acquired
just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the
localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of
solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of
gravitational instability occurring on planetary scales. This study discusses the significance of this finding for
planet formation and its potential connection with the outbursting state of V960 Mon.
Bright radio emission_from_an_ultraluminous_stellar_mass_microquasar_in_m31Sérgio Sacani
1) A new ultraluminous X-ray source (ULX) was detected in the galaxy M31 with a peak X-ray luminosity exceeding 10^39 erg s^-1.
2) Radio observations found highly variable radio emission on timescales of minutes to days, indicating an extremely compact emission region.
3) The X-ray and radio properties of this source are consistent with stellar-mass black hole accretion near or above the Eddington limit, powered by a relativistic jet as seen in Galactic microquasars.
A continuum from_clear_to_cloudy_hot_jupiter_exoplanets_without_primordial_wa...Sérgio Sacani
Uma pesquisa de 10 exoplanetas quentes, do tamanho de Júpiter, conduzida com os telescópios Spitzer e Hubble da NASA levou uma equipe de astrônomos a resolverem um mistério que já durava algum tempo – por que alguns desses mundos têm menos água do que o esperado? A descoberta, oferece novas ideias sobre uma vasta coleção de atmosferas planetárias na nossa galáxia e sobre como os planetas são formados.
Dos quase 2000 planetas confirmados orbitando outras estrelas, um subconjunto deles são planetas gasosos com características similares ao planeta Júpiter, mas, como suas órbitas são muito próximas de suas estrelas, eles são terrivelmente quentes.
A proximidade desses exoplanetas das suas estrelas, faz com que seja difícil observá-los. Devido a essa dificuldade, o Hubble só conseguiu explorar poucos desses exoplanetas, chamados de Júpiteres Quentes, no passado. Esses estudos iniciais descobriram que alguns planetas possuem menos água do que era previsto pelos modelos atmosféricos.
Uma equipe internacional de astrônomos tem atacado o problema fazendo o maior catálogo espectroscópico de atmosferas de exoplanetas até o momento. Todos os planetas no catálogo seguem órbitas orientadas de modo que o planeta passa em frente da estrela quando visto da Terra. Devido a esse trânsito, parte da luz da estrela viaja pela atmosfera externa do exoplaneta. “A atmosfera deixa sua impressão digital única na luz da estrela, que nós podemos estudar, quando ela chega até nós”, explicou a coautora Hannah Wakeford, do Goddard Space Flight Center da NASA , em Greenbelt, Maryland.
NGC 680 and NGC 5557 are early-type galaxies that were observed with deep optical imaging to study their outer morphologies. NGC 680 exhibits extended plumes and tails that appear connected to HI gas, as well as arcs and shells. NGC 5557 has a gigantic 160 kpc long narrow tail containing three star-forming objects. The features suggest that each galaxy underwent a major wet merger over 1-2 Gyr ago, with NGC 5557's merger dominating its formation history and making it a slow rotator, while NGC 680 rotates faster.
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U...Sérgio Sacani
During the formation and evolution of the Solar System, significant
numbers of cometary and asteroidal bodies were
ejected into interstellar space1,2. It is reasonable to expect that
the same happened for planetary systems other than our own.
Detection of such interstellar objects would allow us to probe
the planetesimal formation processes around other stars, possibly
together with the effects of long-term exposure to the
interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known
interstellar object, discovered by the Pan-STARRS1 telescope
in October 2017 (ref. 3). The discovery epoch photometry
implies a highly elongated body with radii of ~ 200 × 20 m
when a comet-like geometric albedo of 0.04 is assumed. The
observable interstellar object population is expected to be
dominated by comet-like bodies in agreement with our spectra,
yet the reported inactivity of 'Oumuamua implies a lack
of surface ice. Here, we report spectroscopic characterization
of ‘Oumuamua, finding it to be variable with time but similar
to organically rich surfaces found in the outer Solar System.
We show that this is consistent with predictions of an insulating
mantle produced by long-term cosmic ray exposure4.
An internal icy composition cannot therefore be ruled out by
the lack of activity, even though ‘Oumuamua passed within
0.25 au of the Sun.
This document provides an overview of the atmospheres of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune). It discusses the composition and structure of their atmospheres based on equilibrium cloud condensation models. The atmospheres contain temperature minima at the tropopause, above which temperatures increase due to absorption of sunlight, and below which temperatures increase with depth due to convection. While early models predicted ammonia and water cloud decks, spacecraft observations have since directly observed ammonia clouds on Jupiter but found they are short-lived, suggesting other cloud composition processes.
This document summarizes research that used gravitational lensing to study dusty starburst galaxies in the early universe. Key findings include:
- ALMA observations of 26 extremely bright millimeter-selected galaxies found spectral lines confirming redshifts in 23, with at least 10 at z > 4.
- High-resolution ALMA imaging showed the galaxies are strongly lensed by foreground galaxies, with magnifications of 4-22x.
- Correcting for magnification, the starburst galaxies have luminosities over 1012 solar luminosities, implying star formation rates over 500 solar masses per year.
- The findings more than double the number of spectroscopically confirmed ultra-luminous galaxies known at z
Radio imaging obserations_of_psr_j1023_0038_in_an_lmxb_stateSérgio Sacani
Uma estrela super densa formada depois da explosão de uma supernova está expelindo poderosos jatos de material no espaço, sugerem pesquisas recentes.
Num estudo publicado no dia 6 de Agosto de 2015, uma equipe de cientistas na Austrália e na Holanda descobriram poderosos jatos sendo expelidos de uma sistema estelar duplo conhecido como PSR J1023+0038.
Pensava-se anteriormente que os únicos objetos no universo capazes de formar jatos poderosos eram os buracos negros.
O sistema PSR J1023+0038 contém uma estrela extremamente densa que os astrônomos chamam de estrela de nêutrons, numa órbita próxima com uma estrela normal.
Ela foi identificada primeiro como uma estrela de nêutrons em 2009, mas foi somente quando a equipe de pesquisa observou a estrela com o rádio telescópio Very Large Array nos EUA em 2013 e 2014 que eles perceberam que a estrela estava produzindo jatos mais fortes do que se esperava.
Os astrônomos James Miller-Jones, do International Centre for Radio Astronomy Research (ICRAR), disse que as estrelas de nêutrons podem ser pensadas como cadáveres estelares.
“Elas são formadas quando uma estrela massiva esgota todo o seu combustível e vira uma supernova, e as partes centrais da estrela colapsam sobre sua própria gravidade”, disse ele.
“Essas coisas tem normalmente entre uma vez e meia a massa do Sol e somente entre 10 a 15 km de diâmetro, de modo que são extremamente densas”.
Similar to An irradiated-Jupiter analogue hotter than the Sun (20)
Compositions of iron-meteorite parent bodies constrainthe structure of the pr...Sérgio Sacani
Magmatic iron-meteorite parent bodies are the earliest planetesimals in the Solar System,and they preserve information about conditions and planet-forming processes in thesolar nebula. In this study, we include comprehensive elemental compositions andfractional-crystallization modeling for iron meteorites from the cores of five differenti-ated asteroids from the inner Solar System. Together with previous results of metalliccores from the outer Solar System, we conclude that asteroidal cores from the outerSolar System have smaller sizes, elevated siderophile-element abundances, and simplercrystallization processes than those from the inner Solar System. These differences arerelated to the formation locations of the parent asteroids because the solar protoplane-tary disk varied in redox conditions, elemental distributions, and dynamics at differentheliocentric distances. Using highly siderophile-element data from iron meteorites, wereconstruct the distribution of calcium-aluminum-rich inclusions (CAIs) across theprotoplanetary disk within the first million years of Solar-System history. CAIs, the firstsolids to condense in the Solar System, formed close to the Sun. They were, however,concentrated within the outer disk and depleted within the inner disk. Future modelsof the structure and evolution of the protoplanetary disk should account for this dis-tribution pattern of CAIs.
Signatures of wave erosion in Titan’s coastsSérgio Sacani
The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it isunclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theo-retical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion,but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titanremain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively dis-cern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combinelandscape evolution models with measurements of shoreline shape on Earth to characterize how differentcoastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that theshorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded bywaves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates atfetch lengths of tens of kilometers.
SDSS1335+0728: The awakening of a ∼ 106M⊙ black hole⋆Sérgio Sacani
Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a ∼ 106M⊙ black hole (BH) that is currently in the process of ‘turning on’. Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1−W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux ∼ 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a ∼ 106M⊙ AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGNobserved in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour. Key words. galaxies: active– accretion, accretion discs– galaxies: individual: SDSS J133519.91+072807.4
Discovery of An Apparent Red, High-Velocity Type Ia Supernova at 𝐳 = 2.9 wi...Sérgio Sacani
We present the JWST discovery of SN 2023adsy, a transient object located in a host galaxy JADES-GS
+
53.13485
−
27.82088
with a host spectroscopic redshift of
2.903
±
0.007
. The transient was identified in deep James Webb Space Telescope (JWST)/NIRCam imaging from the JWST Advanced Deep Extragalactic Survey (JADES) program. Photometric and spectroscopic followup with NIRCam and NIRSpec, respectively, confirm the redshift and yield UV-NIR light-curve, NIR color, and spectroscopic information all consistent with a Type Ia classification. Despite its classification as a likely SN Ia, SN 2023adsy is both fairly red (
�
(
�
−
�
)
∼
0.9
) despite a host galaxy with low-extinction and has a high Ca II velocity (
19
,
000
±
2
,
000
km/s) compared to the general population of SNe Ia. While these characteristics are consistent with some Ca-rich SNe Ia, particularly SN 2016hnk, SN 2023adsy is intrinsically brighter than the low-
�
Ca-rich population. Although such an object is too red for any low-
�
cosmological sample, we apply a fiducial standardization approach to SN 2023adsy and find that the SN 2023adsy luminosity distance measurement is in excellent agreement (
≲
1
�
) with
Λ
CDM. Therefore unlike low-
�
Ca-rich SNe Ia, SN 2023adsy is standardizable and gives no indication that SN Ia standardized luminosities change significantly with redshift. A larger sample of distant SNe Ia is required to determine if SN Ia population characteristics at high-
�
truly diverge from their low-
�
counterparts, and to confirm that standardized luminosities nevertheless remain constant with redshift.
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...Sérgio Sacani
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...Sérgio Sacani
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDSSérgio Sacani
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Anti-Universe And Emergent Gravity and the Dark UniverseSérgio Sacani
Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional ‘dark’ gravitational force describing the ‘elastic’ response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton’s constant and the Hubble acceleration scale a0 = cH0, and provide evidence for the fact that this additional ‘dark gravity force’ explains the observed phenomena in galaxies and clusters currently attributed to dark matter.
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Microbial interaction
Microorganisms interacts with each other and can be physically associated with another organisms in a variety of ways.
One organism can be located on the surface of another organism as an ectobiont or located within another organism as endobiont.
Microbial interaction may be positive such as mutualism, proto-cooperation, commensalism or may be negative such as parasitism, predation or competition
Types of microbial interaction
Positive interaction: mutualism, proto-cooperation, commensalism
Negative interaction: Ammensalism (antagonism), parasitism, predation, competition
I. Mutualism:
It is defined as the relationship in which each organism in interaction gets benefits from association. It is an obligatory relationship in which mutualist and host are metabolically dependent on each other.
Mutualistic relationship is very specific where one member of association cannot be replaced by another species.
Mutualism require close physical contact between interacting organisms.
Relationship of mutualism allows organisms to exist in habitat that could not occupied by either species alone.
Mutualistic relationship between organisms allows them to act as a single organism.
Examples of mutualism:
i. Lichens:
Lichens are excellent example of mutualism.
They are the association of specific fungi and certain genus of algae. In lichen, fungal partner is called mycobiont and algal partner is called
II. Syntrophism:
It is an association in which the growth of one organism either depends on or improved by the substrate provided by another organism.
In syntrophism both organism in association gets benefits.
Compound A
Utilized by population 1
Compound B
Utilized by population 2
Compound C
utilized by both Population 1+2
Products
In this theoretical example of syntrophism, population 1 is able to utilize and metabolize compound A, forming compound B but cannot metabolize beyond compound B without co-operation of population 2. Population 2is unable to utilize compound A but it can metabolize compound B forming compound C. Then both population 1 and 2 are able to carry out metabolic reaction which leads to formation of end product that neither population could produce alone.
Examples of syntrophism:
i. Methanogenic ecosystem in sludge digester
Methane produced by methanogenic bacteria depends upon interspecies hydrogen transfer by other fermentative bacteria.
Anaerobic fermentative bacteria generate CO2 and H2 utilizing carbohydrates which is then utilized by methanogenic bacteria (Methanobacter) to produce methane.
ii. Lactobacillus arobinosus and Enterococcus faecalis:
In the minimal media, Lactobacillus arobinosus and Enterococcus faecalis are able to grow together but not alone.
The synergistic relationship between E. faecalis and L. arobinosus occurs in which E. faecalis require folic acid
Immersive Learning That Works: Research Grounding and Paths ForwardLeonel Morgado
We will metaverse into the essence of immersive learning, into its three dimensions and conceptual models. This approach encompasses elements from teaching methodologies to social involvement, through organizational concerns and technologies. Challenging the perception of learning as knowledge transfer, we introduce a 'Uses, Practices & Strategies' model operationalized by the 'Immersive Learning Brain' and ‘Immersion Cube’ frameworks. This approach offers a comprehensive guide through the intricacies of immersive educational experiences and spotlighting research frontiers, along the immersion dimensions of system, narrative, and agency. Our discourse extends to stakeholders beyond the academic sphere, addressing the interests of technologists, instructional designers, and policymakers. We span various contexts, from formal education to organizational transformation to the new horizon of an AI-pervasive society. This keynote aims to unite the iLRN community in a collaborative journey towards a future where immersive learning research and practice coalesce, paving the way for innovative educational research and practice landscapes.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Mechanisms and Applications of Antiviral Neutralizing Antibodies - Creative B...Creative-Biolabs
Neutralizing antibodies, pivotal in immune defense, specifically bind and inhibit viral pathogens, thereby playing a crucial role in protecting against and mitigating infectious diseases. In this slide, we will introduce what antibodies and neutralizing antibodies are, the production and regulation of neutralizing antibodies, their mechanisms of action, classification and applications, as well as the challenges they face.
An irradiated-Jupiter analogue hotter than the Sun
1. Nature Astronomy
natureastronomy
https://doi.org/10.1038/s41550-023-02048-z
Article
Anirradiated-Jupiteranaloguehotter
thantheSun
Na’ama Hallakoun 1
, Dan Maoz2
, Alina G. Istrate 3
, Carles Badenes4
,
Elmé Breedt 5
, Boris T. Gänsicke 6
, Saurabh W. Jha 7
, Bruno Leibundgut8
,
Filippo Mannucci 9
, Thomas R. Marsh6,14
, Gijs Nelemans 3,10,11
,
Ferdinando Patat8
& Alberto Rebassa-Mansergas 12,13
Planetsorbitingclosetohotstarsexperienceintenseextreme-ultraviolet
radiation,potentiallyleadingtoatmosphereevaporationandtothermal
dissociationofmolecules.However,thisextremeregimeremainsmainly
unexploredduetoobservationalchallenges.Onlyasingleknownultra-hot
giantplanet,KELT-9b,receivesenoughultravioletradiationformolecular
dissociation,withaday-sidetemperatureof~4,600 K.Analternative
approachusesirradiatedbrowndwarfsashot-Jupiteranalogues.With
atmospheresandradiisimilartothoseofgiantplanets,browndwarfs
orbitingclosetohotEarth-sizedwhitedwarfstarscanbedirectlydetected
abovetheglareofthestar.Herewereportobservationsrevealing
anextremelyirradiatedlow-masscompaniontothehotwhitedwarf
WD 0032–317.Ouranalysisindicatesaday-sidetemperatureof~8,000 K,
andaday-to-nighttemperaturedifferenceof~6,000 K.Theamountof
extreme-ultravioletradiation(withwavelengths100–912 Å)receivedby
WD0032–317Bisequivalenttothatreceivedbyplanetsorbitingclosetostars
ashotaslateB-typestars,andabout5,600timeshigherthanthatofKELT-9b.
Withamassof~75–88 Jupitermasses,thisnear-hydrogen-burning-limit
objectispotentiallyoneofthemostmassivebrowndwarfsknown.
Whenaplanetorbitsveryclosetoastar,thestrongtidalforcesitexpe-
riencestendtosynchronizeitsorbitalandrotationalperiods,perma-
nently locking one side of the planet facing the star (‘tidal locking’).
The planet’s ‘day-side’ hemisphere is then continuously exposed to
direct radiation. Depending on the heat redistribution on the planet
surface,thiscanleadtoextremetemperaturedifferencesbetweenthe
day and night sides of the planet, and to thermal dissociation of the
moleculesontheplanet’sdayside1,2
.Outofthefewdozenultra-hotgiant
planetsdiscoveredsofar3
,onlyKELT-9breceivesultravioletradiation
high enough in amount for molecular dissociation, with a day-side
temperature of ~4,600 K (ref. 4).
Our knowledge of planetary systems around hot massive stars
is extremely limited. These stars have few spectral lines, which are
significantlybroadenedbytheirrapidrotationandbystellaractivity5
,
making high-precision radial-velocity measurements challenging.
Suchmeasurementsarecrucialforplanetdetectionandconfirmation,
Received: 30 April 2023
Accepted: 7 July 2023
Published online: xx xx xxxx
Check for updates
1
Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot, Israel. 2
School of Physics and Astronomy, Tel-Aviv University,
Tel-Aviv, Israel. 3
Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, the Netherlands. 4
Department of Physics and Astronomy
and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, Pittsburgh, PA, USA. 5
Institute of Astronomy,
University of Cambridge, Cambridge, UK. 6
Department of Physics, University of Warwick, Coventry, UK. 7
Department of Physics and Astronomy, Rutgers,
The State University of New Jersey, Piscataway, NJ, USA. 8
European Southern Observatory, Garching, Germany. 9
INAF – Osservatorio Astrofisico di
Arcetri, Firenze, Italy. 10
Institute for Astronomy, KU Leuven, Leuven, Belgium. 11
SRON, Netherlands Institute for Space Research, Leiden, the Netherlands.
12
Departament de Física, Universitat Politècnica de Catalunya, Castelldefels, Spain. 13
Institut d’Estudis Espacials de Catalunya, Ed. Nexus-201, Barcelona,
Spain. 14
Deceased: Thomas R. Marsh. e-mail: naama.hallakoun@weizmann.ac.il
2. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
Results
Newfollow-updatathatwehaveobtainedwithUVES,insettingssimilar
to the original SPY spectra, reveal the presence of a highly irradiated
low-masscompanion,evidentbythepresenceofBalmeremissionlines
in antiphase with the primary white dwarf absorption lines (Fig. 1 and
Extended Data Figs. 1 and 2). The companion’s emission in this tidally
locked system is only detected when its heated day side is facing us,
while the radiation coming from the cooler night-side hemisphere
remains hidden in the glare of the white dwarf in the observed wave-
lengthrange.TheoriginalSPYspectrawerefortuitouslyobtainedwhen
thecompanion’snightsidewasvisible,hidingtheday-sideemission.We
haveextractedandfittedtheradial-velocitycurvesofthewhitedwarf
and the companion and found an orbital period of about 2.3 hours
(Table 1 and Extended Data Figs. 3 and 4). We only detect hydrogen
emission lines from the companion, similarly to other systems with
highlyirradiatedcompanions13–15
,althoughwenotethatemissionlines
from metals have been detected in other similar systems16–18
.
Determiningthewhitedwarfmass
To convert the radial-velocity fit parameters into the physical prop-
erties of the system, we need to assume a mass for the white dwarf.
The effective temperature and the surface gravity of the white dwarf
(Table 1) have been previously estimated based on an atmos-
pheric fit to the original SPY UVES observations in 200019
. These
parameters can be converted into a mass, a radius and a cooling
age using theoretical evolutionary tracks, by assuming a specific
white-dwarf core composition. While ‘normal’ white dwarfs have
cores composed of carbon and oxygen, white dwarfs with masses
below ~0.45 M⊙ are considered low-mass white dwarfs, and could
not have formed via single-star evolution as their progenitor
main-sequence lifetime is longer than the age of the Galaxy. Such
white dwarfs are generally thought to have helium cores, a result of
and hence known planets are scarce around stars more massive than
~1.5 M⊙. The difficulty in detecting ultra-hot Jupiters and directly
examining their atmospheres limits our ability to test theoretical
atmospherical models.
An alternative approach uses irradiated brown dwarfs as
hot-Jupiteranalogues6–8
.Despitebeingmoremassivethangiantplan-
ets,browndwarfshavecomparablesizes.Binarysystemsconsistingof
a brown dwarf and a white dwarf (for example, ref. 9) are of particular
interest, as intense irradiation by a hot white dwarf is possible due to
thesmallradiusofthewhitedwarf,whichpermitsveryclosecompan-
ion orbits without contact. At the same time, the same small sizes of
white dwarfs (with radii an order of magnitude smaller than those of
brown dwarfs) makes them many orders of magnitude less luminous
than massive stars, revealing the companion above the glare of the
star. Since the host white dwarf is much hotter than the brown dwarf,
it also dominates the light at different ranges of the electromagnetic
spectrum—white dwarfs emit mostly in the ultraviolet and optical
regions,whilebrowndwarfsemitmostlyintheinfrared.
WD0032–317isahot(~37,000 K)low-mass(~0.4 M⊙)whitedwarf.
Its high effective temperature indicates that only ~1 million years
(Myr) have passed since its progenitor star became a white dwarf.
High-resolutionspectraoftheobjectwereobtainedintheearly2000s
during the type-Ia supernova progenitor survey (SPY)10
, that was car-
riedusingtheUltra-Violet-VisualEchelleSpectrograph(UVES)11
ofthe
European Southern Observatory (ESO) Very Large Telescope (VLT) at
Paranal,Chile.Thesedatashowedasignificantradial-velocityshiftof
itshydrogenHαabsorptionline,causedbythereflexmotioninduced
by the presence of a close companion, flagging WD 0032–317 as a
potentialdoublewhitedwarfsysteminthecandidatelistofMaozand
Hallakoun12
.Aweaknear-infraredexcessinthearchivalspectralenergy
distributionofWD0032–317notedinref.12hintedthatthecompanion
couldactuallybeabrowndwarfratherthananotherwhitedwarf.
–400 –300 –200 –100 0 100 200 300 400
Velocity (km s–1
)
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
Orbital
phase
–300
–200
–100
0
100
200
300
Velocity
(km
s
–1
)
–25
0
25
0 0.2 0.4 0.6 0.8 1.0
Orbital phase
–50
0
50
Residuals
(km
s
–1
)
a b
Fig.1|Phasedradial-velocitycurvesofWD0032–317. a,TrailedUVESspectrum
fortheHαlineofWD0032–317(bluerepresentslowerfluxesandyellow
representshigherfluxes),foldedovertheorbitalperiod(P = 8340.9090 s).The
primaryabsorptionisclearlyseeninblue.Theemissionfromthecompanion
(inyellow)appearsinantiphasewiththeprimaryandisvisibleonlyfromthe
irradiateddayside,betweenorbitalphases~0.2–0.8.Its‘inverted’shape,evident
especiallynearquadrature,istheresultofNLTEeffects58
.b,Radial-velocity
curves(toppanel)ofthewhitedwarf(bluecircles)andtheirradiatedcompanion
(reddiamonds),foldedovertheorbitalperiod(P = 8340.9090 s).Theprimary’s
(secondary’s)best-fitcurveismarkedbythebluedashed(reddotted)lineon
bothpanels.Thebottompanelsshowtheresidualsofthewhitedwarfcomponent
(middle)andtheirradiatedcompanion(bottom).Theerrorbarsshowthe
standarddeviation.Theillustrationsonthetopofb demonstratethesystem’s
configurationateachorbitalphase.
3. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
their nucleosynthetic evolution having been truncated by binary
interactions (for example, ref. 20). Alternatively, if the white dwarf
mass is not extremely low (~0.3 M⊙), intermediate-mass progeni-
tors (≳2.1 M⊙) in binary systems (or undergoing extreme mass loss
through stellar winds) can leave behind a hybrid-core white dwarf,
that is a carbon–oxygen core surrounded by a thick helium layer
(forexample,refs.21–23).SincethemassofWD0032–317isinthelow-
mass range (~0.4 M⊙), we have considered the implications of assum-
ing helium- (He) and hybrid-core white dwarfs in our analysis.
Fittingthespectralenergydistributionofthesystem
To look for photometric variability, we obtained photometric data in
multiple wavelength bands using the 1 m Las Cumbres Observatory
GlobalTelescope(LCOGT)network24
.Inaddition,weretrievedarchival
lightcurvesfromNASA’sTransitingExoplanetSurveySatellite(TESS)25
andWide-FieldInfraredSurveyExplorer(WISE)26
.Thelightcurvesshow
a clear sinusoidal modulation resulting from the changing phases,
from the observer’s viewpoint, of the irradiated hemisphere of the
companion.Thephotometricperiodisconsistentwiththatobtained
from the radial-velocity curves, with no detected eclipses (Extended
Data Figs. 5 and 6).
We have estimated the companion’s radius and its night- and
day-side effective temperatures by fitting the spectral energy dis-
tribution of the system with a combination of a white-dwarf model
spectrum and a brown-dwarf model spectrum for the cooler night
side, and with a black-body spectrum for the day side (Fig. 2 and
Extended Data Figs. 7, 8 and 9). We note that the actual day-side
spectrum of WD 0032–317 is not expected to exactly follow that of
a black-body, as different wavelength ranges probe different opti-
cal depths with different pressures27
. To account for the system’s
orbital inclination we have included an additional fitting parameter
indicating the fraction of night/day contamination. Depending on
the white dwarf core model used, the companion’s heated day-side
temperature ranges between ~7,250 and 9,800 K—as hot as an A-type
star—with a night-side temperature of ~1,300−3,000 K, or a tem-
perature difference of ~6,000 K—about four time as large as that
of KELT-9b28
. The night-side temperature range covers T through
M dwarfs. The ‘equilibrium’ black-body temperature of the irradi-
ated companion (neglecting its intrinsic luminosity and albedo and
assuming it is in thermal equilibrium with the external irradiation)
is about 5,100 K, hotter than any known giant planet (Fig. 3), and
~1,000 K hotter than KELT-9b4
, resulting in an ~5,600 times higher
extreme-ultraviolet flux. We note that the irradiated companion of
the hot white dwarf NN Serpentis has an even higher equilibrium
temperature of ~6,000 K (ref. 16) (but only about three times the
amountofextreme-ultravioletradiationreceivedbyWD0032–317B).
However, with a mass of 0.111 ± 0.004 M⊙ the companion of NN Ser-
pentis is a bona fide main-sequence star rather than a brown dwarf
or a near-hydrogen-burning-limit object (Fig. 4).
Near-infraredspectroscopy
We obtained a pair of low-resolution near-infrared spectra using the
Gemini South’s FLAMINGOS-2 spectrograph29
, taken near orbital
phases 0 and 0.35 (Extended Data Fig. 10). As expected27
, the slope of
thecompanion’sspectraatthiswavelengthrangeisdominatedbythe
irradiated hemisphere’s black-body tail at all orbital phases (because
of the relatively low inclination of the system). However, due to the
lowsignal-to-noiseratioandpossibletelluriccontamination,wecould
not confidently identify any finer features, which are expected at the
few-percentlevelinthiswavelengthrange.Atorbitalphase0.35,when
alargerfractionoftheirradiatedhemisphereisvisible,apossibleweak
Brackett 10 → 4 hydrogen line emission is detected. Future infrared
spectroscopicobservationswithahighsignal-to-noiseratio(forexam-
ple with the James Webb Space Telescope), taken at different orbital
phases, should be able to resolve these features.
Table 1 | Properties of the WD 0032–317 system
General system parameters
RA Right ascension (J2000)1
00h34m49.8573s
dec. Declination (J2000)1
−31∘
29′
52.6858′′
ϖ Parallax1
(mas) 2.320±0.053
d Distance1
(pc) 431.1±9.8
E (B − V) Extinction2
(mag) 0.0176±0.0007
White dwarf parameters3
T1 Effective temperature (K) 36,965±100
log g1 Surface gravity (cms−2
) 7.192±0.014
Model-independent orbital parameters4
P Orbital period (s) 8340.9090±0.0013
K1 Primary radial velocity semi-amplitude
(kms−1
)
53.4±1.7
Kem Secondary’s emission radial velocity
semi-amplitude (kms−1
)
257.1±1.1
γ1 Primary mean velocity (kms−1
) 20.5±1.4
γ2 Secondary mean velocity (kms−1
) 9.1±1.0
Δγ Mean velocity difference (kms−1
) 11.4±1.7
ϕ0 Initial orbital phase 0.000+0.012
−0.011
T0 Ephemeris (BJD
(TDB); E is the cycle
number)
2451803.6673(11)+
0.096531354(15)E
Model-dependent orbital parameters
White-dwarf core model
He5
Hybrid6
M1 Primary mass (M⊙) 0.4187±0.0047 0.386±0.014
R1 Primary radius (R⊙) 0.02703±0.00024 0.02616±0.00024
t1 Primary cooling
age (Myr)
0.91±0.30 1.8±1.6
M2 Secondary mass
(M⊙)
0.0812±0.0029 0.0750±0.0037
R2 Secondary
radius (R⊙)
0.0789+0.0085
−0.0083
0.0747+0.0085
−0.0079
q Mass ratio 0.1939±0.0065 0.1943±0.0065
K2 Secondary
radial velocity
semi-amplitude
(kms−1
)
275.6±2.4 275.1±2.5
a Orbital separation
(R⊙)
0.7028±0.0026 0.6841±0.0083
i Orbital inclination
(deg)
63.3±1.1 66.4±2.0
fcont Night/day
contamination
fraction
0.182+0.033
−0.034
0.227+0.028
−0.028
Teq Secondary
equilibrium
temperature (K)
5126±28 5111±41
Tnight Secondary
night-side
temperature (K)
1970+840
−670
2035+927
−716
Tday Secondary
day-side
temperature (K)
7900+780
−650
8835+955
−794
Source: 1
Gaia DR3 2
https://irsa.ipac.caltech.edu/applications/DUST/ ref. 66 3
Atmospheric
fit19 4
Radial-velocity fit 5
Helium-core white dwarf evolutionary tracks 6
Hybrid-core
white dwarf evolutionary tracks Data are presented as median values±standard
deviation.
4. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
Discussion
The main source of uncertainty in determining the properties of the
system remains the white dwarf core composition, with the compan-
ion mass ranging from ~0.075 M⊙ for a hybrid-core white dwarf and
~0.081 M⊙ foraHe-corewhitedwarf,bothnearthehydrogen-burning
limit.Althoughtheoreticalevolutionarymodelsplacethislimitsome-
where between 0.070–0.077 M⊙ for solar metallicity, observations
suggest a higher limit30,31
. Since the precise hydrogen-burning limit
depends on the metallicity32
, rotation33
and formation history of the
brown dwarf34
, the companion could still be a very massive brown
dwarf. Inconsistencies between the predicted theoretical mass and
the much-higher measured dynamical mass of some T dwarfs have
also been reported35
. The three-dimensional velocity of the system,
~50 km s−1
, indicates a somewhat older age than that of the Galactic
thin disc, which might point to a relatively lower metallicity. When
placed on a mass–radius relation diagram (Fig. 4), it is clear that WD
0032–317Bisaborderlineobject,withasmallerradiusthanexpected
for a non-degenerate hydrogen-burning star. Nevertheless, as at this
mass range near the hydrogen-burning limit its intrinsic luminosity
is negligible compared to the external radiation it experiences, the
difference between a brown dwarf and a very low-mass star is merely
semantic for the purpose of studying highly irradiated substellar
objects and planets.
To form the low-mass white dwarf, the companion must have
contributedtotheunbindingoftheredgiant’senvelope.Withamass
well above the critical limit of ~0.01–0.03 M⊙ in the case of a He-core
whitedwarf,thecompanionwasmassiveenoughtohavesurvivedthe
processwithoutgettingevaporated36
.Thesmallradiusofthecompan-
ion,indicatinganageofatleastafewbillionyears(Gyr;Fig.4),stands
in contrast with the white dwarf ~1 Myr cooling age—the time that has
passed since it lost its envelope. This suggests that the companion
was not significantly heated during the common-envelope phase,
indicatingaratherefficientenvelopeejection.Assumingthefullenergy
required to unbind the envelope came from orbital sources, the pro-
genitorofaHe-corewhitedwarfcouldhavebeenquitealow-massstar
of~1.3 M⊙ (ref.36).Hybrid-corewhitedwarfs,ontheotherhand,arethe
descendants of more massive and compact giants, with much larger
bindingenergies(forexample,ref.37).Thiswouldrequireunbinding
theenvelopewithamuchhigherefficiencyinorderforthecompanion
tosurviveandgettotheobservedcloseorbit,andmightargueagainst
ahybridnatureofthewhitedwarf(Methods).
WD 0032–317 offers a rare glimpse into the early days of a post-
common-envelope binary and to an unexplored parameter space of
irradiatedsubstellarandplanetaryobjects.UnlikeactualhotJupiters
or irradiated brown dwarfs with larger host stars (such as hot subd-
warfs, for example, ref. 15), for which spectroscopic observations are
onlypossibleduringeclipsesineclipsingsystems,thelow-masscom-
panionshouldbevisibleintheinfraredwavelengthrangethroughout
theorbitalcycle.Futurehigh-resolutiontime-resolvedspectroscopic
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
λ
4
f
λ
(erg
s
–1
cm
–2
Å
3
)
White dwarf
Night-side 2,000 K brown-dwarf model ×4
Composite phase-0 model
Day-side 7,900 K black-body model
Composite phase-0.5 model
GALEX
LCOGT day
LCOGT night
WISE W1 day
WISE W1 night
0
0.25
Day
1,000 10,000
2,000 3,000 5,000 20,000 50,000
Wavelength (Å)
–0.2
0
Night
Residuals
(erg
s
–1
cm
–2
Å
3
)
Fig.2|ObservedspectralenergydistributionforWD0032–317comparedto
thebest-fittingcompositetheoreticalmodelspectraofawhitedwarfanda
blackbodyorabrowndwarf.ThearchivalGalaxyEvolutionExplorer(GALEX)
ultravioletphotometry,wherethecontributionfromthecompanionis
negligible,appearsasbluesquare-shapederrorbars.Minimalandmaximal
photometricvaluesindifferentbands,extractedfromthelightcurves,appearas
green-shadedcircle-shapederrorbarsforLCOGT’sr′,i′andzbands,andas
red-shadeddiamond-shapederrorbarsfortheWISEW1band.Atheoretical
modelspectrumofahydrogen-dominatedwhitedwarfwithaneffective
temperatureof37,000 Kandasurfacegravity log g = 7.2 (ref.63)isshownin
dashedlightblue.Thebest-fittingbrown-dwarf64,65
(forthenightside,with
log g = 5.5andthecommonlogarithmofthemetalabundancerelativeto
hydrogencomparedtothatoftheSun,[M/H],is −0.5)andblack-body(fortheday
side)modelsareplottedinsolidpurpleanddottedorange,respectively.The
theoreticalspectrawerescaledusingthesystem’sdistancemeasuredbytheGaia
missionandtheestimatedcomponentradii(assumingaHe-corewhitedwarf,see
ExtendedDataFig.7forthehybridmodel).Thebrown-dwarfmodelisshown
multipliedbyafactorof4,tofitthedisplayedrange.Thecompositemodelofthe
systematorbitalphase0(0.5)isplottedinsoliddarkgrey(black).Theunits
shownontheyaxisarethefluxperwavelength,λ,multipliedbyλ4
,forvisual
clarity.Thebottompanelsshowtheresidualsoftheday-side(middle)andthe
night-side(bottom)fits.Theerrorbarsintheresidualplotsshowthestandard
deviationandtakeintoaccountboththephotometricandthemodel
uncertainties.
0.1 1 10
Orbital separation (R☼)
0
1,000
2,000
3,000
4,000
5,000
Equilibrium
temperature
(K)
WD 1032+011
SDSS J1205–0242
SDSS J1231+0041
SDSS J1411+2009
EPIC 21223532
GD 1400
WD 0137–349
WD 0837+185
NLTT 5306
SDSS J1557+0916
ZTF J0038+2030
Gaia 0007–1605
KELT-9b
WD 0032–317
Fig.3|EquilibriumtemperatureofWD0032–317comparedtootherknown
systems.Equilibriumtemperatureasafunctionoftheorbitalseparationforthe
known(blackcircles)andcandidate(greytriangle)whitedwarf–browndwarf
systems(seeMethodsforreferences)andhotJupiterplanets(light-greycircles)3
.
WD0032–317ismarkedwitharedstar-shapedsymbol.Theultra-hotJupiter
KELT-9b4
appearsasabluediamond.Theerrorbarsshowthestandarddeviation
andareplottedforallthewhitedwarf–browndwarfsystems(butaresmallerthan
themarkersizeinsome).
5. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
observations of the system covering the near-infrared range would
revealindetailthegradualtransitionfromtheabsorptivefeature-rich
nightsidetotheemissivedayside(forexample,ref.27;ExtendedData
Fig. 10), directly probing the effects of the extreme temperature dif-
ference and heat transport efficiency between the hemispheres. The
broadwavelengthcoverage,sensitivetodifferentpressurelevelsinthe
atmosphere, would reveal the three-dimensional atmospheric struc-
ture, including temperature inversion effects27,38
. Since the system is
tidallylocked,theorbitalperiodprovidesadirectmeasurementofthe
companionrotationperiod.Thiscanhelpinunderstandingtheroleof
rotationontheatmosphericstructureandcirculationinfast-rotating
extremelyirradiatedgasgiants8
.
Methods
Spectroscopic observations with UVES
Thetwooriginal10 minexposuresofWD0032–317wereobtainedon
16–17September2000withUVES11
oftheESOVLTatParanal,Chile,as
a part of the SPY programme. The instrument was used in a dichroic
mode, covering most of the range between 3200 Å and 6650 Å, with
two ~80 Å gaps around 4580 Å and 5640 Å, and a spectral resolution
of R ≈ 18,500 (0.36 Å at Hα)39
. The data featured Balmer absorption
lines from the primary white dwarf only, with no contribution from
a companion. In a previous work, we measured a radial-velocity shift
of 38.1 ± 3.8 km s−1
between the two epochs and flagged it for future
follow-upasapotentialdoublewhitedwarf,notingthataweakinfrared
excessinthespectralenergydistributioncouldindicatethepresenceof
abrown-dwarfcompanion12
.Wehaveacquiredanadditional16spectra
with UVES using similar settings, from June to August 2019 and from
September to December 2020. The pipeline-processed reduced data
wereobtainedfromtheESOScienceArchiveFacility.Thenewspectra
revealed the presence of a highly irradiated low-mass companion,
evident in Balmer emission lines at antiphase with the primary white
dwarf(Fig.1aandExtendedDataFigs.1and2).
PhotometricobservationswithLCOGT
To look for photometric variability, we obtained multiband photom-
etry on 2–6 August 2021 and 14 October 2022 using the 1 m LCOGT
network24
. The observations were performed using the Sinistro cam-
eras on the 1 m telescopes in Cerro Tololo (LSC), Chile, and in Suther-
land(CPT),SouthAfrica.Eachobservationsequenceconsistedof50 s
exposures with an ~1 min cadence, spanning ~1–2 orbital cycles, each
sequenceusingadifferentfilter(SDSSr′andi′,andPan-STARRSzandy).
Thesystemwasnotdetectedinthey-bandimages,andwehenceomit
theybandfromthediscussion.
The images were reduced by the BANZAI pipeline40
, including
bad-pixel masking, bias and dark subtraction, flat-field correction,
sourceextractionandastrometriccalibration(usinghttp://astrometry.
net/).ThesourceextractionwasperformedusingtheSourceExtraction
andPhotometry(SEP)Pythonpackage41–43
.Wethenchosesourceswith
asignal-to-noiseratiobetween100and1,000(toavoidfaintandsatu-
ratedstars,respectively)andafluxstandarddeviationsmallerthan30
timesthemeanfluxerror(toavoidlightcurveswithlong-termtrends)
ascomparisonstars.Therawlightcurvesofthetargetandofanearby
reference star (right ascension = 00 h 35 m 02.2571 s, declina-
tion = −31∘
31′
19.028′′
) were corrected for transparency variations by
dividing them by the median flux of the comparison stars. The target
light curve was then flux-calibrated using synthetic photometry
extractedfromthelow-resolutionBlue/RedPhotometer(BP/RP)spec-
traofthetargetandreferencestarsinthethirddatareleaseofGaia44–46
,
taking into account the colour difference between the two stars. We
dividedthecorrectedlightcurveofthetargetbythatofthereference
star,andmultiplieditbythereferencestarfluxineachband(calculated
using the Gaia spectrum) and by a calibration factor that keeps the
mediancountratioequaltotheGaiasyntheticphotometryratiointhe
band.Thetimestampswereshiftedtomid-exposureandtransformed
tothebarycentricframeusingAstropy.
PhotometricobservationswithTESSandWISE
ThesystemwasobservedtwicebyTESS25
,onceinshort-cadencemode
(120 s exposures) in 2018 from 23 August to 20 September (Sector
02),andagaininfast-cadencemode(20 sexposures)in2020from26
Augustto21September(Sector29).Thepipeline-reducedlightcurves
wereobtainedfromtheMikulskiArchiveforSpaceTelescopes(MAST).
Anadditional27epochsofthesysteminthe3.4 μm W1bandwere
obtained by WISE26
in 2010. The pipeline-reduced light curve was
obtained from the Infrared Processing and Analysis Center (IPAC)
InfraredScienceArchive(IRSA).
Whitedwarfparameters
Theeffectivetemperatureandsurfacegravityofthewhitedwarfcom-
ponent were estimated in a previous study as T1 = 36,965 ± 100 K and
log g1 = 7.192 ± 0.014 , respectively, based on an atmospheric fit to
theoriginalSPYUVESspectrafrom200019
.Thiswasdonebyfittingthe
Balmerabsorptionlinesusingtheoreticalmodelspectra.Inthisfitthe
0 0.025 0.050 0.075 0.100 0.125 0.150 0.175 0.200
Mass (M☼)
0.050
0.075
0.100
0.125
0.150
0.175
0.200
0.225
0.250
Radius
(R
☼
)
55 Myr
142 Myr
1 Gyr
10 Gyr
100 Myr
150 Myr
5 Gyr
Carmichael97
Parsons et al.98
NN Ser
SDSS J0104+1,535
WD0032–317, He
WD0032–317, Hybrid
Fig.4|Brown-dwarfandlow-massstarsmass–radiusrelation.Known
transitingbrowndwarfsandverylow-massstarsorbitingmain-sequencestars
appearasgreyerrorbars97
,whileknowneclipsingMdwarfsorbitingwhitedwarfs
appearasgreenerrorbars98
.ThedottedgreylinesaretheoreticalATMO2020
isochrones73
ofdifferentagesandsolarmetallicity.Thedashedgreylinesare
theoreticalBT-DUSTYisochrones64,65
ofdifferentages,with[M/H] = −0.5.
ThepositionofWD0032–317ismarkedbyaredcircle(assumingaHe-core
whitedwarf),andabluesquare(assumingahybrid-corewhitedwarf).Thelow-
metallicityhaloobject,SDSSJ0104+1535,whichisthemostmassiveknownbrown
dwarf99
,isshownbytheorangetriangleandtheultra-hotM-dwarfcompanionof
NNSer16
isshownbythepurpledown-pointingtriangle,forreference.Theerror
barsshowthestandarddeviation.
6. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
authorsassumedasinglewhitedwarf,butsincebothSPYepochswere
taken,bychance,nearorbitalphase0(seebelow)whentheirradiated
day side of the companion is hidden, this assumption is valid. These
parameters can be converted into a mass, a radius and a cooling age
using theoretical evolutionary tracks by assuming a specific white
dwarfcorecomposition:helium(He)orhybrid.Theevolutionarytracks
were computed using the Modules for Experiments in Stellar Astro-
physics (MESA) code47–51
, similarly to Istrate et al.52
for He-core white
dwarfsandtoZenatietal.22
forhybrid-corewhitedwarfs(Istrateetal.,
manuscript in preparation). The computed models include rotation
and element diffusion. We created white dwarfs with various
hydrogen-envelopemasses,rangingfromthecanonicalvalueresulting
from binary evolution models (a few 10−4
M⊙) down to 10−10
M⊙, by
artificially removing mass from the canonical white dwarf. We note
that when we used canonical, stable mass-transfer models (similar to
the Althaus et al.20
models), the radius of the white dwarf was overes-
timated. For this reason we adopted the variable-envelope models
here, in an attempt to mimic the results of a common envelope. The
mass, radius and cooling age of the white dwarf, interpolated using
thesetwomodels,appearinTable1.
To narrow down the possible parameter space, we estimated the
whitedwarfradiususingtheGALEXultravioletmeasurements,inwhich
thefluxcontributionfromthecompanionshouldbenegligible,as
RWD =
√
√
√
fλ,meas
fλ,theo
d, (1)
where fλ,meas is the measured white dwarf flux, fλ,theo is the extinction-
corrected theoretical white dwarf flux and d is the system’s dis-
tance from Gaia DR3 (Table 1). The estimated white dwarf radius
is 0.025954 ± 0.00060 R⊙ based on the GALEX FUV point and
0.027137 ± 0.00062 R⊙ basedontheGALEXNUVpoint.Wethusadopted
thefullrange,0.0266 ± 0.0012 R⊙,asthewhitedwarfradius.
Another constraint for the theoretical models comes from the
predicted surface abundance. As the white dwarf is relatively hot,
gravitational settling timescale dictates a minimum white dwarf
mass for which, at this effective temperature, the surface is hydro-
gen dominated. The maximal allowed helium surface abundance
was estimated by generating synthetic white dwarf spectra with dif-
ferent helium abundances using the spectral synthesis programme
SYNSPEC (v.50)53
, based on a one-dimensional, horizontally homo-
geneous, plane-parallel, hydrostatic model atmosphere created with
the TLUSTY programme (v.205)54–56
. The models were computed in
local thermodynamic equilibrium (LTE), using the Tremblay tables57
for hydrogen line broadening. The synthetic spectra were convolved
with a 0.36 Å-wide Gaussian, to mimic the UVES spectral resolution.
Wefindthataheliumsurfaceabundanceof~10−3
relativetohydrogen
would have been detected in the UVES spectra. Since no helium lines
are detected, the helium surface abundance must be ≲10−3
relative to
hydrogen.Wethereforeexcludedmodelswherethehydrogensurface
abundanceis≲1.
Radial-velocityanalysis
Radial velocity extraction. As mentioned above, the only spectral
features originating from the system that are detected in the UVES
data are hydrogen Balmer lines—in absorption from the white dwarf
and in emission from the companion. The companion emission has
a complex ‘inverted’ shape (Fig. 1a and Extended Data Fig. 1) due to
non-LTE(NLTE)effects58
,asseeninothersystemswithlow-massirradi-
atedcompanions(forexample,ref.16).Theinvertedlineprofileisseen
inalloftheBalmerlines.Sinceithasthebestradial-velocityaccuracy,
weonlyusetheHαlineinourfit.
As the system rotates, the centres of the spectral lines of both of
its components are shifted periodically in opposite directions due to
Doppler effect. To extract the radial velocities of the white dwarf and
thecompanion,wefittedaregionof±1,000 km s−1
aroundtheposition
oftheHαline,ineachindividualepoch,withacombinationofaquad-
ratic dependence of the flux on the velocity (fitting the wings of the
fullHαlineprofile)andthreeGaussians—oneinabsorption,fittingthe
NLTEcoreoftheHαlineofthewhitedwarf,andapairofGaussianswith
invertedintensitiessharingthesamemean,fittingtheinverted-coreof
theHαemissionfromthecompanion(ExtendedDataFig.1):
I (v) = a0 + a1v + a2v2
− I1 exp (−
v−v1
2σ2
1
)
+I2,em exp (−
v−v2
2σ2
2,em
) − I2,ab exp (−
v−v2
2σ2
2,ab
) ,
(2)
wherev1 andv2 aretheradialvelocitiesofthewhitedwarfandthecom-
panion, respectively. I1 and σ1 are the intensity and width of the white
dwarfNLTEcoreabsorption,respectively.I2,em andI2,ab aretheintensities
of the emission and absorption line components of the companion,
respectively, while σ2,em and σ2,ab are the respective line component
widths.Alltheparameterswerefittedindividuallyforeachepoch.We
notethatthefittedGaussianwidthsσ1, σ2,ab andσ2,em variedby~30%,70%
and 20%, respectively. This behaviour is known from similar systems
(forexample,refs.16,59),andislikelycausedbyhighopticaldepthand
saturationeffectsinthelines.
Since the companion’s emission is only visible when its irradi-
ated day side is facing us, we first examined each epoch by eye and
marked the epochs in which only the white dwarf component is seen.
We then fitted these epochs with a combination of the quadratic
dependence and a single Gaussian, omitting the companion’s contri-
butioninequation(2).ThefitwasperformedusingSCIPY’sCURVE_FIT
bounded non-linear least squares Trust Region Reflective algorithm.
The best-fitting line profiles are shown in Extended Data Fig. 1. The
radial velocity uncertainty was estimated based on the covariance
matrix of each fit. Each epoch was assigned a barycentric timestamp
at mid-exposure and the velocities were shifted to the barycentric
frameusingAstropy.
Orbital solution.Theradialvelocitycurvesofthewhitedwarfandthe
companionweremodelledusing
v1,2 = γ1,2 ± K1,2 sin [2π (ϕ − ϕ0)] , (3)
where γ1,2 and K1,2 are the systematic mean velocities and the
radial-velocity semi-amplitudes of the white dwarf and companion,
respectively,andϕ0 istheinitialorbitalphase.Sincethecompanion’s
emission originates from its irradiated side, we measure in fact the
centre-of-lightradialvelocity,andnotthecentre-of-massradialveloc-
ity.Wedenotetheradial-velocitysemi-amplitudeofthecompanion’s
centre-of-lightKem,andcorrectittothecentre-of-massframebelow.
To probe the orbital period of the system over a wide range of
values,wefirstexaminedtheLomb-Scargleperiodogramoftheradial
velocity series of the white dwarf component using ASTROPY. The
Lomb-Scargleperiodogramcomputesthebest-fitmodelparameters,
⃗
θ,atagivenfrequency,f,forthemodel:
y (t; f, ⃗
θ) = θ0 +
nterms
∑
n=1
[θ2n−1 sin(2πn ft) + θ2n cos(2πn ft)] , (4)
where t is the time, and nterms+1 is the number of fitted parameters.
Assuming a circular orbit (nterms = 1), and subtracting the weighted
mean of the input data, δ, before the fit, we can use the Lomb-Scargle
fit parameters to estimate the radial-velocity semi-amplitude of the
whitedwarf,
K1 = √θ2
1
+ θ2
2
, (5)
7. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
theinitialorbitalphase,
ϕ0 = − arctan (
θ2
θ1
) , (6)
andthesystematicmeanvelocityofthewhitedwarf,
γ1 = θ0 + δ. (7)
The Lomb-Scargle periodogram of the radial velocity curve of the
white dwarf is shown in Extended Data Fig. 3. The best-fitting orbital
period is P = 8340.3046 ± 0.0075 s, and the model parameters are
K1 ≈ 52.7 km s−1
, ϕ0 ≈ 0.98andγ1 ≈ 19.8 km s−1
.
We then used the Lomb-Scargle solution as an initial guess for
a Markov Chain Monte Carlo (MCMC) fit of the full radial-velocity
data, including that of the companion. The fitting was performed
using EMCEE, the Python implementation of the Affine Invariant
MCMC Ensemble sampler60,61
. The MCMC algorithm minimizes the
χ2
value of the fit over a six-dimensional parameter space defined by
theorbitalperiod(P),theinitialorbitalphase(ϕ0),theradial-velocity
semi-amplitudesofthewhitedwarf(K1)andthecompanion’semission
(Kem),themeanradialvelocityofthewhitedwarf(γ1),andthedifference
between the mean velocities of the companion and the white dwarf
(Δγ ≡ γ1 − γ2).TheMCMCrunincludedanensembleof25‘walkers’with
100,000iterationseach.Theinitialpositionofeachwalkerwasdrawn
from a Gaussian distribution around the initial guess, with a width of
10−10
fortheorbitalperiod,0.01fortheinitialorbitalphaseand0.1for
therestofthefitparameters.Theautocorrelationlengthsoftheresult-
ing MCMC chains ranged from 70 to 81 iterations. We thus discarded
the first 161 iterations of each walker (‘burn-in’) and kept every 34
iterationsoftheremainingwalkerchain(‘thinning’).Attheendofthe
process, each fit parameter had a final chain with a length of 73,400.
Figure1bshowstheradialvelocitycurvebestfit,whileExtendedData
Fig.4showstheone-andtwo-dimensionalprojectionsoftheposterior
probabilitydistributionsofthefitparameters.Thebest-fittingparam-
etersaregiveninTable1.
WenotethattherelativelylargeuncertaintyofΔγ = 11.4 ± 1.7 km s−1
preventsusfromestimatingameaningfulsecondarymass/radiusratio
basedonthegravitationalredshift(M2/R2 = M1/R1 − Δγc/G).However,it
is consistent within 0.9σ with the theoretical gravitational redshift of
aHe-corewhitedwarf(9.86 ± 0.14 km s−1
)andwithin1.2σwiththatofa
hybrid-corewhitedwarf(9.39 ± 0.35 km s−1
),basedonthewhitedwarf
parametersinTable1.
Photometryanalysis
Modellingthelightcurvesofanon-eclipsingsystemwithanirradiated
companion is a challenging task that depends on many poorly con-
strained, highly degenerate parameters, and on the unknown details
of the heat redistribution processes in the irradiated companion. We
thusdeferthelight-curvemodellingtofutureworkandfocusinstead
on a comparison of the companion’s day and night sides. We have fit-
ted the light curves with a simple sinusoidal model to guide the eye
using SCIPY’s CURVE_FIT (Extended Data Fig. 5). The Lomb-Scargle
periodogram of each light curve, computed using Astropy, is shown
in Extended Data Fig. 6. The frequency of the highest peak in all of
the light curves is consistent with the one of the radial-velocity curve
(ExtendedDataFig.3).
Thecalibratedlightcurveswerephase-foldedovertheperiodand
ephemeris obtained from the radial-velocity analysis (Table 1), and
binned into 50 bins by taking the median of each bin as the value and
1.48 times the median absolute deviation divided by the square root
of the number of data points in the bin as the error. The normalized
phase-folded light curves are shown in Extended Data Fig. 5. A clear
irradiationeffectisseeninthelightcurves,withnodetectedellipsoidal
modulation(expectedatthe~1%level)oreclipses(theexpectedeclipse
duration is ~9 min, or about 6% of the orbital period). The reflection
contributionshouldbeatalevelof~0.1%(ref.62).
The minimum (maximum) flux of the system was measured by
takingthemedianflux ± 0.05aroundorbitalphase0(0.5)ineachband.
The error was calculated as 1.48 times the median absolute deviation
of the flux divided by the square root of the number of data points.
Given the rather sparse and noisy WISE W1-band light curve, in this
bandwetookthemedianflux ± 0.1aroundorbitalphases0and0.5as
the minimum and maximum flux values, and 1.48 times the median
absolutedeviationoftheminimalfluxlevelastheerrorforbothvalues.
We then combined these extremum measurements in the r′, i′, z and
W1bandswiththearchivalGALEXFUVandNUVmeasurements(where
thecontributionfromtheirradiatedcompanionisnegligible),toesti-
mate the companion’s radius and night- and day-side effective tem-
peratures.Thiswasdonebyfittingthespectralenergydistributionof
thesystemwithacombinationofawhite-dwarfmodelspectrumwith
a brown-dwarf model spectrum for the cooler night side, and with a
black-body spectrum for the day side (Extended Data Fig. 7). For the
whitedwarfweusedahydrogen-dominatedDAmodelwithaneffective
temperatureof37,000 Kandlog g = 7.2(ref.63),andforthecompanion
we used BT-DUSTY models with effective temperatures ranging from
1,000to6,000 K(refs.64,65).Were-ranthefitusingdifferentsurface
gravityandmetallicityvaluesforthebrown-dwarfmodels(log g of5.0
and 5.5, and [M/H] of −1.0, −0.5 and 0). Models with [M/H] = −1.0 were
availableonlyfor log g = 5.5atthistemperaturerange.Allmodelswere
obtained from the Spanish Virtual Observatory (http://svo.cab.
inta-csic.es). As the white dwarf model truncates at a wavelength of
25,000 Å, we have extrapolated it to 50,000 Å assuming a
Rayleigh-Jeans λ−4
slope, where λ is the wavelength. The combined
theoretical models were scaled using the estimated radii and the sys-
tem’sdistancefromGaiaDR3,andwerereddenedtoaccountforextinc-
tionbyGalacticdust(usinghttps://irsa.ipac.caltech.edu/applications/
DUST/)66
.Wethenfittedtheobservedspectralenergydistributionwith
the band-integrated theoretical flux using the EMCEE package. The
MCMC algorithm minimizes the χ2
value of the fit over a four-
dimensional parameter space defined by the companion’s night- and
day-sideeffectivetemperatures(T
night
2
andT
day
2
,respectively),thecom-
panion’s radius (R2) and the fraction of night/day-side contamination
duetothesystem’sinclinationandthecompanion’sheatdistribution
(fcont).TheMCMCrunincludedanensembleof25‘walkers’with40,000
iterations each. The initial position of each walker was drawn from a
Gaussian distribution with a width of 0.3 around the initial guess
(T
night
2
= 3000K,T
day
2
= 6000K,R2 = 0.08 R⊙ andfcont = 0.2).Theresulting
minimal χ2
value was slightly lower for the fit that uses brown-dwarf
models with log g = 5.5 (although insignificantly, by ~0.004). Among
the log g = 5.5 model fits, models with [M/H] = −0.5 had slightly lower
minimalχ2
valuesassumingaHe-corewhitedwarf(by~0.012compared
to[M/H] = 0andby~0.004comparedto[M/H] = −1.0),or[M/H] = −1.0
assuming a hybrid-core white dwarf (by ~0.003 compared to
[M/H] = −0.5 and by ~0.004 compared to [M/H] = 0). We have thus
adopted the results using values of log g = 5.5 and [M/H] = −0.5 for a
He-core white dwarf, and log g = 5 and [M/H] = −1.0 for a hybrid-core
whitedwarf.TheautocorrelationlengthsoftheresultingMCMCchains
ranged from 54 to 69 iterations. We thus discarded the first 125 (137)
iterations of each walker (‘burn-in’), and kept every 26 (27) iterations
oftheremainingwalkerchain(‘thinning’)forthefitassumingaHe-core
(hybrid)whitedwarfradius.Attheendoftheprocess,eachfitparam-
eter had a final chain with a length of 38,325 (36,900). The best-fit
models are plotted in Extended Data Fig. 7 and listed in Table 1.
ExtendedDataFigs.8and9showtheone-andtwo-dimensionalprojec-
tionsoftheposteriorprobabilitydistributionsofthefitparameters.
CorrectingKem forthecentreofmass
As mentioned above, the companion’s emission originates from the
surface of its irradiated side. The radial velocities measured from the
8. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
emission line thus impose a lower limit on the centre-of-mass radial
velocities16
. The radial velocity semi-amplitude of the centre of mass,
K2,canbeestimatedby
K2 =
Kem
1 − f (1 + q)
R2
a
, (8)
whereq = M2/M1 isthebinarymassratio,R2 istheradiusofthecompan-
ion, a is the orbital separation and 0 ≤ f≤ 1 is a constant that depends
uponthelocationofthecentreoflight67
.Foranopticallythicklinesuch
astheHαline,wecanassumef ≈ 0.5(asdemonstratedbyrefs.16,67).
TheorbitalseparationcanbecalculatedusingKepler’slaw,
a = (
P2
4π2
G (M1 + M2))
1/3
, (9)
where P is the orbital period, G is the gravitational constant, M1 is the
white dwarf mass and M2 = qM1 is the mass of the companion. Since
q = M2/M1 = K1/K2, there is only a single q value that is consistent with
bothequations(8)and(9),giventhemeasuredvaluesofKem,PandR2,
andtheassumedvaluesofM1 andf.Table1liststhederivedvaluesofq
and K2 foreachwhitedwarfcorecomposition.
Wethencalculatetheorbitalinclination,i:
i = arcsin [(
P
2πGM1
(K1 + K2)
2
K2)
1
3
] , (10)
assuming a circular orbit. The implied possible orbital inclination
rangeislistedinTable1.
Equilibriumtemperature
The ‘equilibrium’ temperature of the irradiated companion (neglect-
ing its intrinsic luminosity and albedo, and assuming it is in thermal
equilibrium with the external irradiation) is listed in Table 1 for each
whitedwarfcorecomposition.Itisdefinedas
Teq ≡ T1
√
R1
2a
, (11)
where T1 and R1 are the effective temperature and radius of the white
dwarfandaistheorbitalseparation68
.
Near-infraredspectroscopywithFLAMINGOS-2
We obtained a pair of low-resolution near-infrared spectra, around
orbital phases 0 and 0.35, on 9 June 2022 using the FLAMINGOS-2
spectrograph29
onGeminiSouthinCerroPachón,Chile.Theobserva-
tions were carried out using the HK grism, HK filter and a 0.36 arcsec
slit, covering the H- and K-band region (~13, 000−21,500 Å) with a
spectral resolution of R ≈ 900. Each spectrum was composed of five
2-minexposures.Thetelescopewasnoddedalongtheslitbetweenthe
exposurestofacilitatetheskysubtraction.Thedataofthetargetandof
thetelluricstandardHD225187werereducedandtherawcountspectra
were extracted using the GEMINI IRAF package v.1.14, following the
GeminiF2LongslitTutorial(https://gemini-iraf-flamingos-2-cookbook.
readthedocs.io/en/latest/Tutorial_Longslit.html).
We then used the SPARTA Python package (https://github.com/
SPARTA-dev/SPARTA) to retrieve and broaden to the FLAMINGOS-2
spectral resolution a PHOENIX model spectrum of the telluric star.
We normalized it by dividing it by its continuum shape (obtained by
interpolatingovertheline-freeregionsinthespectrum)andapplied
to it the expected Doppler shift at the time of the observations. We
manually scaled the normalized model spectrum so that its absorp-
tion lines agree with those in the raw count spectrum of the telluric
star.Finally,wedividedthetelluricstar’srawspectrumbythescaled
model spectrum to remove the star’s intrinsic absorption lines from
the observed telluric spectrum. We then divided the raw spectrum
of WD 0032–317 by the telluric spectrum, taking the different expo-
sure times into account, to obtain the relative count spectrum of
WD 0032–317. We calibrated the flux using the telluric star’s archival
H-bandmagnitude,assumingablack-bodymodel.Finally,webinned
the result by taking the median of every four data points (Extended
Data Fig. 10).
Formationhistory
Weestimatethewhitedwarfprogenitormass,MMS,as36
MMS ≈
1
2
M1 (1 +
√
1 +
2αλRRGM2
M1a0
) , (12)
whereM1 isthewhitedwarfmass,M2 isthemassofthecompanionand
wehaveassumedM2 ≪ MMS − M1.RRG istheradiusoftheprogenitorred
giant in the beginning of the spiral-in phase. In the case of a He-core
whitedwarf,itcanbeapproximatedas69
RRG ≈ 103.5
(
M1
M⊙
)
4
R⊙, (13)
correspondingtoRRG,He ≈ 97 R⊙.Aftertheenvelopeejection,theorbital
separation shrinks with time due to gravitational-wave emission. The
orbitalseparationimmediatelyaftertheenvelopeejection,a0,isesti-
matedas70
a0 = [a4
+
256
5
G3
c5
M1M2 (M1 + M2) Δt]
1
4
, (14)
whereaisthepresent-dayorbitalseparation,andΔtisthetimethathas
passed since the envelope ejection, approximated as the white dwarf
coolingage,t1.Giventheyoungcoolingageofthewhitedwarf(~1 Myr),
the orbital separation has changed by merely ~0.01%. α ≡ ΔEbind/ΔEorb
is a parameter describing the envelope ejection efficiency and λ < 1 is
a weighting factor that depends on the structure of the red giant. For
λ = 0.5andαrangingbetween0.5and4(refs.71,72),wegetawhitedwarf
progenitormassrangingbetween~1−2.4 M⊙ foraHe-corewhitedwarf.
Thesmallradiusofthecompanionindicatesanageofatleastafew
billionyears(Fig.4)73
.Ontheotherhand,thewhitedwarfcoolingage—
thatis,thetimethathaspassedsinceitlostitsenvelope—is~1 Myr.This
suggests that the companion was not significantly heated during the
common-envelopephase,indicatingthattheinternalthermodynamic
energyoftheenvelopedidnotcontributemuchtotheenvelopeejec-
tion(α ≈ 1).Assumingthefullenergyrequiredtounbindtheenvelope
came from orbital sources, the progenitor of a He-core white dwarf
couldhavebeenquitealow-massstarof~1.3 M⊙.
Thecriticalmassabovewhichthecompaniondoesnotevaporate
duringtheenvelopeejectionis36
mcrit = 10[(
MMS − M1
M1
) (
MMS
M⊙
) (
RRG
100R⊙
)]
0.46
MJup, (15)
and ranges between ~0.01–0.03 M⊙ for a He-core white dwarf—well
belowthemassofthecompanion.
Hybrid-corewhitedwarfs,ontheotherhand,arethedescendants
of more massive and compact systems, with a factor ≳5 larger bind-
ing energies (for example, ref. 37). To estimate the envelope binding
energy in the hybrid scenario, we modelled a hybrid progenitor with
a mass of 2.3 M⊙ and a He-core progenitor with a mass of 1.3 M⊙, when
bothreachedaHe-coreof0.4 M⊙.Atthisstage,wefindthatthebinding
energy of the hybrid progenitor is about 26 times larger than that of
the He-core progenitor. For the He-core progenitor we find λHe ≈ 0.7
and αHe ≈ 1.1, while for the hybrid progenitor we find λHybrid ≈ 0.9 and
αHybrid ≈ 31. This would require unbinding the envelope with a much
9. Nature Astronomy
Article https://doi.org/10.1038/s41550-023-02048-z
higherefficiencyinorderforthecompaniontosurviveandgettothe
observed close orbit, and might argue against a hybrid nature of the
white dwarf. However, since the exact physical processes governing
the common envelope evolution are unknown, a hybrid-core white
dwarfcannotbeexcluded.
Thewhitedwarf–browndwarfpopulation
Todate,only12whitedwarf–browndwarfsystemsareknown9,13,14,18,74–84
.
This makes WD 0032–317 the 13th known such system (assuming the
companion is a brown dwarf), with the hottest irradiated companion
(Fig.3).Thereisanadditionalcandidatewhitedwarf–browndwarfsys-
temSDSSJ1231+0041(ref.14),thatsomewhatresemblesWD0032–317
(with an equilibrium temperature ~400 K cooler). However at a dis-
tanceof~1,500 pcandanapparentmagnitudeofG = 20.35(compared
to G = 16.10 of WD 0032–317), it is difficult to obtain time-resolved
spectroscopy for this system and to confirm the nature of the heated
companion. Given this observational challenge, this system cannot
serveasausefulultra-hotJupiteranalogue.
WD 0032–317 was identified as a binary candidate out of a sub-
sample of 439 white dwarfs from the SPY survey12
. Incidentally, WD
0137–349, the first confirmed post-common-envelope white dwarf–
browndwarfbinary,wasalsodiscoveredbyanearlyanalysisoftheSPY
data75,76
,whichincluded~800whitedwarfs.Currentlowerlimitsonthe
whitedwarf–browndwarfbinaryfractionaref ≥ 0.5 ± 0.3%(ref.85)and
f > 0.8 − 2%(ref.86).Giventhatthesebinaryfractionestimateswerefor
all orbital separations, while the radial-velocity changes detectable
by SPY limit the white dwarf–brown dwarf systems that it can find to
≲0.1 AU (ref. 12), the observed incidence is consistent with both of
thesepreviousestimates.
Dataavailability
The UVES spectroscopic data are available through the ESO archive
facility (http://archive.eso.org/cms.html) under programme IDs
165.H-0588(A),0103.D-0731(A)and105.20NQ.001.TheFLAMINGOS-2
spectroscopic data are available through the Gemini Observa-
tory archive (https://archive.gemini.edu) under programme ID
GS-2022A-FT-108. The LCOGT photometric data are available at the
LCOGTsciencearchive(https://archive.lco.global)underprogramme
IDs TAU2021B-004 and TAU2022B-004. The TESS photometric data
are publicly available from the Mikulski Archive for Space Telescopes
(MAST; https://mast.stsci.edu). The WISE photometric data are pub-
liclyavailablefromtheInfraredProcessingandAnalysisCenter(IPAC)
Infrared Science Archive (IRSA; https://irsa.ipac.caltech.edu/). The
whitedwarftheoreticalevolutionarytracksusedintheanalysiswillbe
published in a future publication led by A.G.I. and are available upon
request from the corresponding author. Source data are provided
withthispaper.
Codeavailability
This research has made use of the Python package GAIAXPY (https://
gaia-dpci.github.io/GaiaXPy-website/, https://doi.org/10.5281/
zenodo.7374213), developed and maintained by members of the Gaia
Data Processing and Analysis Consortium (DPAC), and in particular,
CoordinationUnit5(CU5)andtheDataProcessingCentrelocatedatthe
InstituteofAstronomy,Cambridge,UK(DPCI);andASTROPY(http://
www.astropy.org), a community-developed core Python package
for Astronomy87,88
, CORNER89
, EMCEE61
, LIGHTKURVE90
, MATPLOT-
LIB91
, NUMPY92,93
, SCIPY94
, SPARTA (https://github.com/SPARTA-dev/
SPARTA), STSYNPHOT95
, SYNPHOT96
and UNCERTAINTIES (http://
pythonhosted.org/uncertainties/),aPythonpackageforcalculations
withuncertaintiesbyE.O.Lebigot.
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Acknowledgements
We thank S. Shahaf for useful discussions, J. Spyromilio for comments
on the observing proposals and manuscript, J. Pritchard from ESO
User Support for assistance with the observation planning and A.
Binnenfeld for help in verifying the orbital period. This work was
supported by a Benoziyo-prize postdoctoral fellowship (N.H.).
This work was supported by a grant from the European Research
Council (ERC) under the European Union’s FP7 Programme, Grant No.
833031 (D.M.). A.G.I. acknowledges support from the Netherlands
Organisation for Scientific Research (NWO). C.B. acknowledges
support from the National Science Foundation grant no. AST-1909022.
E.B. acknowledges support from the Science and Technology
Facilities Council (STFC) grant no. ST/S000623/1. B.T.G. acknowledges
support from the UK’s Science and Technology Facilities Council
(STFC), grant no. ST/T000406/1. This project has received funding
from the European Research Council (ERC) under the European
Union’s Horizon 2020 research and innovation programme (Grant
agreement no. 101020057). A.R.M. acknowledges support from
the Spanish MINECO grant no. PID2020-117252GB-I00 and from
the AGAUR/Generalitat de Catalunya grant no. SGR-386/2021. F.M.
acknowledges support from the INAF Large Grant ‘Dual and binary
supermassive black holes in the multi-messenger era: from galaxy
mergers to gravitational waves’ (Bando Ricerca Fondamentale INAF
2022), from the INAF project ‘VLT-MOONS’ CRAM 1.05.03.07. Based on
observations collected at the European Southern Observatory under
ESO programmes 165.H-0588(A), 0103.D-0731(A) and 105.20NQ.001.
This research has made use of the services of the ESO Science
Archive Facility. This work makes use of observations from the Las
Cumbres Observatory global telescope network under programme
TAU2021B-004. This work is based on observations obtained at the
international Gemini Observatory, a programme of NSF’s NOIRLab,
which is managed by the Association of Universities for Research in
Astronomy (AURA) under a cooperative agreement with the National
Science Foundation on behalf of the Gemini Observatory Partnership:
the National Science Foundation (United States), National Research
Council (Canada), Agencia Nacional de Investigación y Desarrollo
(Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina),
Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil)
and Korea Astronomy and Space Science Institute (Republic of
Korea). This work was enabled by observations made from the Gemini
North telescope, located within the Maunakea Science Reserve and
adjacent to the summit of Maunakea. We are grateful for the privilege
of observing the Universe from a place that is unique in both its
astronomical quality and its cultural significance. This paper includes
data collected by the TESS mission, which are publicly available from
the Mikulski Archive for Space Telescopes (MAST). Funding for the
TESS mission is provided by the NASA’s Science Mission Directorate.
This research has made use of the VizieR catalogue access tool, CDS,
Strasbourg, France. This research has made use of the Spanish Virtual
Observatory (http://svo.cab.inta-csic.es) supported from Ministerio