Article
Astronomy & Astrophysics
Simon Blouin, Siyi Xu
Summary: Recent studies show that the mass accretion rates of cool, old white dwarfs do not significantly decrease over several billion years of cooling time, indicating the need for mechanisms to consistently deliver planetesimals inside the Roche radius of white dwarfs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Andrew Swan, Scott J. Kenyon, Jay Farihi, Erik Dennihy, Boris T. Gansicke, J. J. Hermes, Carl Melis, Ted von Hippel
Summary: WD0145+234 is a white dwarf accreting metals from a circumstellar disc, with a significant increase in 3-5 μm flux since 2018 that began to decrease by late 2019. Stochastic brightening events during the decline suggest liberation of dust during collisional evolution of circumstellar solids. Emission lines from circumstellar gas support the idea of white dwarf debris discs as sites of collisional gas and dust production.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Simon Blouin
Summary: The absence of detectable external pollution in classical DQ stars is naturally explained by the impact of metal accretion on the atmospheric structure of the white dwarf. Accretion of heavy elements leads to a decrease in atmospheric density, resulting in a sharp drop in carbon abundance and suppression of C-2 Swan bands. This study shows that typical DQ stars that accrete heavy elements from planetary material generally transform directly into DZ stars.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Paula Izquierdo, Odette Toloza, Boris T. Gansicke, Pablo Rodriguez-Gil, Jay Farihi, Detlev Koester, Jincheng Guo, Seth Redfield
Summary: The research focused on the analysis of a metal-polluted, helium-atmosphere white dwarf, GD424, with substantial trace hydrogen. By utilizing a hybrid analysis, the atmospheric parameters were determined and the abundances of 11 photospheric metals were measured. It is suggested that the trace hydrogen observed in GD424 may have been acquired through accretion of water-rich planetary debris in an earlier event.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Alexandre Caron, P. Bergeron, Simon Blouin, S. K. Leggett
Summary: In this study, we present a analysis of 2880 cool white dwarfs within 100 pc of the Sun and cooler than T-eff similar to 10 000 K, with rigorous photometry and parallax measurement. We find evidence of a transformation from DA stars to He-atmosphere white dwarfs in the range T-eff = 6500-5500 K, while most DC white dwarfs have H atmospheres at even cooler temperatures (T-eff ? 5200 K). We also discover that DQ, DZ, and DC white dwarfs may form a more homogeneous population than previously believed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
N. P. Gentile Fusillo, C. J. Manser, Boris T. Gaensicke, O. Toloza, D. Koester, E. Dennihy, W. R. Brown, J. Farihi, M. A. Hollands, M. J. Hoskin, P. Izquierdo, T. Kinnear, T. R. Marsh, A. Santamaria-Miranda, A. F. Pala, S. Redfield, P. Rodriguez-Gil, M. R. Schreiber, Dimitri Veras, D. J. Wilson
Summary: A survey of planetary remnants using a large number of white dwarfs identified six white dwarfs with gaseous debris discs, highlighting the unique features of three systems. These discoveries shed light on the underlying diversity in gaseous debris disc systems and bring the total number of these objects to 21.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
E. L. Martin, N. Lodieu, C. del Burgo
Summary: The theory of substellar evolution predicts the existence of a mass boundary between lithium and non-lithium brown dwarfs. This study presents new observations of binary systems and confirms the sharp transition in mass for lithium depletion in brown dwarfs as predicted by theoretical calculations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Rebassa-Mansergas, J. Maldonado, R. Raddi, A. T. Knowles, S. Torres, M. Hoskin, T. Cunningham, M. Hollands, J. Ren, B. T. Gansicke, P-E Tremblay, N. Castro-Rodriguez, M. Camisassa, D. Koester
Summary: By analyzing binary stars that have not interacted, the study found a flat age-metallicity relation with a scatter of approximately +/- 0.5 dex around the solar metallicity at all ages. This independently confirms the lack of correlation between age and metallicity in the solar neighborhood observed in previous studies analyzing single main sequence stars and open clusters.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Sophie Dubber, Beth Biller, Loic Albert, Michael Liu, Jessy Jose, Zhoujian Zhang, Wen-Ping Chen, Bhavana Lalchand, Belinda Damian, Tanvi Sharma, Katelyn Allers
Summary: We have spectroscopically confirmed nine M5 or later Serpens Core candidate members using CFHT WIRCam photometry and IRTF SpeX spectroscopy. The latest of these candidates is best fit by an L0 spectral standard, suggesting a mass of about 0.01-0.035M (solar mass). If confirmed as cluster members, they would be among the lowest mass objects ever discovered in the Serpens Core. We performed analysis on the physical properties of the sample and discussed the likely membership of the candidate Serpens Core members.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Klaus Werner, Nicole Reindl, Matti Dorsch, Stephan Geier, Ulisse Munari, Roberto Raddi
Summary: Hot, compact, hydrogen-deficient pre-white dwarfs are rare objects that are believed to be the outcome of either single star evolution or binary star evolution. Their study is important for understanding the physics of thermonuclear flashes and merger events. Spectroscopically, they are divided into three different classes, namely PG1159, O(He), or He-sdO. This study presents a spectroscopic analysis of five such stars and found that some of them have hydrogen content that cannot be explained by current evolution models.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Simon Blouin, Antoine Bedard, Pier-Emmanuel Tremblay
Summary: The Gaia colour-magnitude diagram shows a clear separation between hydrogen-atmosphere white dwarfs and helium-atmosphere white dwarfs during the cooling process. However, the magnitudes of pure-helium atmospheres are too similar to those of pure-hydrogen atmospheres to explain this bifurcation. To explain the observed split, it has been suggested that there must be trace amounts of hydrogen and/or metals in the helium-dominated atmospheres of hydrogen-deficient white dwarfs. This study aims to provide a comprehensive explanation by considering population synthesis simulations, model atmospheres, and evolutionary calculations along with element transport in white dwarf envelopes. The simulations successfully reproduce the bifurcation and highlight the importance of convective dredge-up of carbon in explaining the observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Christopher J. Manser, Erik Dennihy, Boris T. Gansicke, John H. Debes, Nicola P. Gentile Fusillo, J. J. Hermes, Mark Hollands, Paula Izquierdo, B. C. Kaiser, T. R. Marsh, Joshua S. Reding, Pablo Rodriguez-Gil, Dimitri Veras, David J. Wilson
Summary: This study discusses the presence of planetary material in white dwarf atmospheres, particularly focusing on the gaseous component detectable via emission from atomic transitions. The emission profiles of the CaII triplet in a few systems have been shown to be highly variable, with periodic morphological variations likely caused by an asymmetric disc. Additionally, Doppler tomography imaging was used to visualize the asymmetric nature of velocity images generated by gas moving on eccentric orbits.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
C. S. Jeffery, K. Werner, D. Kilkenny, B. Miszalski, I Monageng, E. J. Snowdon
Summary: The Southern African Large Telescope survey has discovered and analyzed eight new very hot white dwarfs and pre-white dwarfs, with effective temperatures exceeding 100,000 K, including two PG1159 stars, one DO white dwarf, three O(He) stars, and two O(H) stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
S. Dalal, F. Kiefer, G. Hebrard, J. Sahlmann, S. G. Sousa, T. Forveille, X. Delfosse, L. Arnold, N. Astudillo-Defru, X. Bonfils, I Boisse, F. Bouchy, V Bourrier, B. Brugger, P. Cortes-Zuleta, M. Deleuil, D. S. Demangeon, R. F. Diaz, N. C. Hara, N. Heidari, M. J. Hobson, T. Lopez, C. Lovis, Martioli, L. Mignon, O. Mousis, C. Moutou, J. Rey, A. Santerne, N. C. Santos, Segransan, P. A. Strom, S. Udry
Summary: This study identifies and characterizes 6 cool Jupiters, 3 brown dwarf candidates, and 16 low-mass stellar companions using radial velocity surveys. The discovery of a new, highly eccentric cool Jupiter, BD+631405 b, adds to the diversity of substellar objects. The findings help constrain models of formation and evolution for substellar objects and low-mass stars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
B. Riaz, W-F Thi, M. N. Machida
Summary: We conducted the first molecular line survey to search for methanol (CH3OH) in 14 Class 0/I protobrown dwarfs (proto-BDs). The results showed emission in 14 CH3OH transition lines, with upper state energy levels ranging from 7-49 K and critical densities of 10(5)-10(9) cm(-3). The high-excitation lines likely probe the warm corino region in the proto-BDs, while the low-excitation lines trace the cold gas. The column density for the cold component is higher than the warm component, and the ortho-to-para ratios of CH3OH range between 0.3 and 2.3.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Chris Evans, Stefano Cristiani, Cyrielle Opitom, Gabriele Cescutti, Valentina D'Odorico, Juan Manuel Alcala, Silvia H. P. Alencar, Sergei Balashev, Beatriz Barbuy, Nate Bastian, Umberto Battino, Pamela Cambianica, Roberta Carini, Brad Carter, Santi Cassisi, Bruno Vaz Castilho, Norbert Christlieb, Ryan Cooke, Stefano Covino, Gabriele Cremonese, Katia Cunha, Andre R. da Silva, Valerio D'Elia, Annalisa De Cia, Gayandhi De Silva, Marcos Diaz, Paolo Di Marcantonio, Heitor Ernandes, Alan Fitzsimmons, Mariagrazia Franchini, Boris T. Gansicke, Matteo Genoni, Riano E. Giribaldi, Andrea Grazian, Camilla Juul Hansen, Fiorangela La Forgia, Monica Lazzarin, Wagner Marcolino, Marcella Marconi, Alessandra Migliorini, Pasquier Noterdaeme, Claudio Pereira, Bogumil Pilecki, Andreas Quirrenbach, Sofia Randich, Silvia Rossi, Rodolfo Smiljanic, Colin Snodgrass, Julian Stuermer, Andrea Trost, Eros Vanzella, Paolo Ventura, Duncan Wright, Tayyaba Zafar
Summary: This paper introduces the scientific motivations for the development of the Cassegrain U-Band Efficient Spectrograph (CUBES) for the Very Large Telescope. It covers a wide range of astronomical topics where current ground-based spectrographs are limited. Each topic's background is presented, and specific technical requirements for the instrument design are identified. The CUBES design aims to greatly improve the efficiency of astronomical spectroscopy over a specific wavelength range, and its predicted performance is compared to existing facilities.
EXPERIMENTAL ASTRONOMY
(2023)
Article
Astronomy & Astrophysics
Mairi W. O'Brien, P-E Tremblay, N. P. Gentile Fusillo, M. A. Hollands, B. T. Gansicke, D. Koester, I Pelisoli, E. Cukanovaite, T. Cunningham, A. E. Doyle, A. Elms, J. Farihi, J. J. Hermes, J. Holberg, S. Jordan, B. L. Klein, S. J. Kleinman, C. J. Manser, D. De Martino, T. R. Marsh, J. McCleery, C. Melis, A. Nitta, S. G. Parsons, R. Raddi, A. Rebassa-Mansergas, M. R. Schreiber, R. Silvotti, D. Steeghs, O. Toloza, S. Toonen, S. Torres, A. J. Weinberger, B. Zuckerman
Summary: We conducted a spectroscopic survey of 248 white dwarf candidates within a distance of 40 pc from the Sun, with 244 of them located in the Southern hemisphere. Using the Very Large Telescope and Southern Astrophysical Research Telescope, we confirmed a total of 246 white dwarfs, with 209 having no previously published spectra. Among the identified white dwarfs, 100 display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, we observed 35 magnetic white dwarfs through Zeeman splitting of their spectral lines.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. Scaringi, M. Monguio, C. Knigge, M. Fratta, B. Gaensicke, P. J. Groot, A. Rebassa-Mansergas, O. Toloza
Summary: This paper presents a sub-arcsec cross-match of Gaia DR3 with IGAPS and UKIDSS, resulting in a catalogue called XGAPS. The XGAPS catalogue provides additional precise photometry to Gaia photometry and has various applications, such as selecting Galactic targets for spectroscopic surveys and identifying specific Galactic populations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Paula Izquierdo, Boris T. Gansicke, Pablo Rodriguez-Gil, Detlev Koester, Odette Toloza, Nicola P. Gentile Fusillo, Anna F. Pala, Pier-Emmanuel Tremblay
Summary: White dwarf photospheric parameters obtained through spectroscopic or photometric analysis often show inconsistencies, with published values only including statistical uncertainties. We analyzed 13 white dwarfs with helium-dominated photospheres using multiple techniques, and found realistic uncertainties for the effective temperature, surface gravity, and relative hydrogen abundance. The mean standard deviations for diverse spectroscopic data were (SEC)sigma T-eff(SEC) = 524 K, (SEC)sigma log g(SEC) = 0.27 dex, and (SEC)sigma log (H/He)(SEC) = 0.31 dex. Photometric fits showed higher mean standard deviations of up to (SEC)sigma T-eff(SEC) = 1210 K and (SEC)sigma log g(SEC) = 0.13 dex. These values are suggested as realistic lower limits for published uncertainties in parameter derivation for similar white dwarfs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
S. G. Parsons, M. S. Hernandez, O. Toloza, M. Zorotovic, M. R. Schreiber, B. T. Gansicke, F. Lagos, R. Raddi, A. Rebassa-Mansergas, J. J. Ren, D. Koester
Summary: Virtually all binaries consisting of a white dwarf with a non-degenerate companion can be classified as close post-interaction systems or wide systems. Binaries with periods between these two extremes can provide valuable information about common envelope efficiency and alternative pathways in the creation of compact binaries. The discovery of three white dwarfs in binaries with evolved subgiant stars sheds light on the formation process of these systems and their future evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Felipe Lagos, Monica Zorotovic, Matthias R. Schreiber, B. T. Gansicke
Summary: The recently discovered system Gaia 0007-1605, consisting of a white dwarf with a brown dwarf companion and a distant white dwarf tertiary, resembles the triple system WD 1856+534, which is the first transiting planet candidate around a white dwarf. The formation of the inner binary in Gaia 0007-1605 could be attributed to either common envelope evolution, triple dynamics, or a combination of both mechanisms. The energy budget and Von Zeipel-Lidov-Kozai oscillations play important roles in understanding the system's current configuration.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Antonio C. Rodriguez, Shrinivas R. Kulkarni, Thomas A. Prince, Paula Szkody, Kevin B. Burdge, Ilaria Caiazzo, Jan van Roestel, Zachary P. Vanderbosch, Kareem El-Badry, Eric C. Bellm, Boris T. Gensicke, Matthew J. Graham, Ashish A. Mahabal, Frank J. Masci, Przemek Mroz, Reed Riddle, Ben Rusholme
Summary: Two new magnetic cataclysmic variables (CVs) have been discovered through crossmatching the eFEDS catalog with photometry data, one of which is pulsating and the other is non-pulsating.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Andrew P. Cooper, Sergey E. Koposov, Carlos Allende Prieto, Christopher J. Manser, Namitha Kizhuprakkat, Adam D. Myers, Arjun Dey, Boris T. Gansicke, Ting S. Li, Constance Rockosi, Monica Valluri, Joan Najita, Alis Deason, Anand Raichoor, M. -Y. Wang, Y. -S. Ting, Bokyoung Kim, Andreia Carrillo, Wenting Wang, Leandro Beraldo e Silva, Jiwon Jesse Han, Jiani Ding, Miguel Sanchez-Conde, Jessica N. Aguilar, Steven Ahlen, Stephen Bailey, Vasily Belokurov, David Brooks, Katia Cunha, Kyle Dawson, Axel de la Macorra, Peter Doel, Daniel J. Eisenstein, Parker Fagrelius, Kevin Fanning, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztanaga, Satya Gontcho A. Gontcho, Julien Guy, Klaus Honscheid, Robert Kehoe, Theodore Kisner, Anthony Kremin, Martin Landriau, Michael E. Levi, Paul Martini, Aaron M. Meisner, Ramon Miquel, John Moustakas, Jundan J. D. Nie, Nathalie Palanque-Delabrouille, Will J. Percival, Claire Poppett, Francisco Prada, Nabeel Rehemtulla, Edward Schlafly, David Schlegel, Michael Schubnell, Ray M. Sharples, Gregory Tarle, Risa H. Wechsler, David H. Weinberg, Zhimin Zhou, Hu Zou
Summary: We describe the Milky Way Survey (MWS), which will be conducted with the Dark Energy Spectroscopic Instrument (DESI), aiming to observe approximately seven million stars and investigate the Galactic structure and stellar evolution. The MWS target selection scheme focuses on the thick disk and stellar halo, including rare stellar types such as white dwarfs, low-mass stars near the Sun, and horizontal branch stars. Our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances are validated using the DESI Survey Validation program (SV) data, showing good agreement with expectations from mock catalogs and previous surveys.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Christopher J. Manser, Boris T. Gansicke, Keith Inight, Akshay Robert, S. Ahlen, C. Allende Prieto, D. Brooks, A. P. Cooper, A. de la Macorra, A. Font-Ribera, K. Honscheid, T. Kisner, M. Landriau, Aaron M. Meisner, R. Miquel, Jundan Nie, C. Poppett, Gregory Tarle, Zhimin Zhou
Summary: A new class of white dwarfs, called DAHe, has been discovered to have Zeeman-split Balmer lines in emission, but the origins of these emission lines are still unknown. By studying a sample of 21 newly identified DAHe systems, researchers have determined the magnetic field strengths and rotation periods of these systems. These DAHe systems cluster together on the Gaia Hertzsprung-Russell diagram and represent about 1% of white dwarfs in that region.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Odette Toloza, Boris T. Gansicke, Laura M. Guzman-Rincon, Tom R. Marsh, Paula Szkody, Matthias R. Schreiber, Domitilla de Martino, Monica Zorotovic, Kareem El-Badry, Detlev Koester, Felipe Lagos
Summary: Research suggests that white dwarfs that accrete from non-degenerate companions exhibit abnormal carbon and nitrogen abundances in their stellar components, indicating they may be descendants of supersoft X-ray binaries. Measuring the carbon-to-nitrogen abundance ratio can provide insights into their past evolution. By analyzing far-ultraviolet spectroscopy of the cataclysmic variable HS 0218 + 3229, it was found that the ratio of carbon-to-nitrogen is about one tenth of the solar value. Other elemental abundances were also estimated, and the system's past was reconstructed. The study predicts that HS 0218 + 3229 will evolve to a period minimum below 76.2 +/- 1 minutes for normal cataclysmic variables.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Rebassa-Mansergas, J. Maldonado, R. Raddi, S. Torres, M. Hoskin, T. Cunningham, M. A. Hollands, J. Ren, B. T. Gansicke, P-E Tremblay, M. Camisassa
Summary: Magnetic activity and rotation are related to the age of low-mass main-sequence stars. The rotational velocities tend to decrease over time, but there are moderately old stars that rotate faster than expected. The activity fractions for stars younger than 5 Gyr range between 10% and 40%, while older stars may also have higher activity fractions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Keith Inight, Boris T. Gaensicke, Elme Breedt, Henry T. Israel, Stuart P. Littlefair, Christopher J. Manser, Tom R. Marsh, Tim Mulvany, Anna Francesca Pala, John R. Thorstensen
Summary: We present a catalogue of 507 cataclysmic variables (CVs) observed in SDSS I to IV, including 70 new classifications. This sample provides unbiased space densities and period distributions for different CV sub-types. The study also reports on peculiar CVs, period bouncers, and CVs with large changes in accretion rates. The catalogue and material included in it will be useful for observational population studies of CVs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Pablo Rodriguez-Gil, Jesus M. Corral-Santana, N. Elias-Rosa, Boris T. Gansicke, Margarita Hernanz, Gloria Sala
Summary: This study presents the first reliable determination of the orbital period of the recurrent nova V2487 Oph. The derived value is significantly shorter than previous claims, making V2487 Oph one of the longest period cataclysmic variables known. The analysis of the spectra suggests that the broad Balmer absorptions in V2487 Oph come from an accretion disc viewed at low inclination.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Multidisciplinary Sciences
Ilaria Caiazzo, Kevin B. Burdge, Pier-Emmanuel Tremblay, James Fuller, Lilia Ferrario, Boris T. Gansicke, J. J. Hermes, Jeremy Heyl, Adela Kawka, S. R. Kulkarni, Thomas R. Marsh, Przemek Mroz, Thomas A. Prince, Harvey B. Richer, Antonio C. Rodriguez, Jan van Roestel, Zachary P. Vanderbosch, Stephane Vennes, Dayal Wickramasinghe, Vikram S. Dhillon, Stuart P. Littlefair, James Munday, Ingrid Pelisoli, Daniel Perley, Eric C. Bellm, Elme Breedt, Alex J. Brown, Richard Dekany, Andrew Drake, Martin J. Dyer, Matthew J. Graham, Matthew J. Green, Russ R. Laher, Paul Kerry, Steven G. Parsons, Reed L. Riddle, Ben Rusholme, Dave I. Sahman
Summary: White dwarfs, the dense remnants of dead stars, have a mass comparable to the Sun compressed into the size of a planet.The composition of a white dwarf's atmosphere can change as it cools, with some transitioning from a hydrogen-dominated atmosphere to a helium-dominated one. The observed white dwarf ZTF J203349.8+322901.1 shows a peculiar nature, with one side of its atmosphere dominated by hydrogen and the other by helium. This may be caused by the presence of a small magnetic field, creating temperature, pressure, or mixing variations.
Article
Astronomy & Astrophysics
Na'ama Hallakoun, Dan Maoz, Alina G. Istrate, Carles Badenes, Elme Breedt, Boris T. Gansicke, Saurabh W. Jha, Bruno Leibundgut, Filippo Mannucci, Thomas R. Marsh, Gijs Nelemans, Ferdinando Patat, Alberto Rebassa-Mansergas
Summary: We report observations of an extremely irradiated low-mass companion to the hot white dwarf WD 0032-317. Our analysis indicates a day-side temperature of about 8000K and a day-to-night temperature difference of about 6000K. The extreme-ultraviolet radiation received by WD 0032-317B is equivalent to that received by planets orbiting close to hot stars and about 5600 times higher than that of KELT-9b. With a mass of about 75-88 Jupiter masses, this near-hydrogen-burning-limit object is potentially one of the most massive brown dwarfs known.