Article
Astronomy & Astrophysics
M. A. Gomez-Munoz, L. Sabin, R. Raddi, R. D. Wells
Summary: White dwarf stars are often associated with central stars of planetary nebulae, but they are difficult to observe in optical bands due to their high temperatures and low luminosities. In this study, we identified 74 hot white dwarf candidates using data from GALEX and IGAPS and analyzed their spectral energy distribution and infrared colors to support the accuracy of the identification. Ground-based observations are needed to confirm their nature.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
N. P. Gentile Fusillo, P-E Tremblay, E. Cukanovaite, A. Vorontseva, R. Lallement, M. Hollands, B. T. Gansicke, K. B. Burdge, J. McCleery, S. Jordan
Summary: In this study, a catalogue of white dwarf candidates was presented based on Gaia Early Data Release 3 (EDR3) and compared with samples from Sloan Digital Sky Survey (SDSS). The distribution of these candidates was mapped in the Gaia absolute magnitude-colour space, and a probability of being a white dwarf was calculated for over 1.3 million sources. High-confidence white dwarf candidates were selected based on these calculations and stellar parameters were estimated using synthetic atmospheric models. The catalogue was found to have an overall completeness limit of 93% for white dwarfs with G <= 20 mag and effective temperature (T-eff) > 7000 K at high Galactic latitudes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Olivier Vincent, P. Bergeron, P. Dufour
Summary: The next generation of spectroscopic surveys is expected to provide spectra for hundreds of thousands of white dwarf candidates. A data-driven pipeline for fast and automatic selection, and spectroscopic classification of WD candidates has been proposed. The pipeline shows improved accuracy and completeness over existing algorithms and can classify the primary spectroscopic type of WD candidates with about 90% accuracy, also detecting main sequence companions. The pipeline has been applied to Gaia Data Release 3 cross-matched with SDSS Data Release 17, resulting in the identification of 424,096 high-confidence WD candidates and the first catalogue of automated and quantifiable classification for 36,523 WD spectra, which are available online.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Kevin Wang, Thomas Kupfer, Brad N. Barlow
Summary: We conducted a systematic search for periodic variables in the hot subdwarf catalogue and made new discoveries including a mass-transferring hot subdwarf binary candidate. Traditional methods of determining astrophysical variability may miss a significant proportion of variable targets, especially sinusoidal variability. Variable hot subdwarfs show a reddening effect and are found in a higher proportion near the Galactic plane.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yan Luo, Xiao-Jun Wu, Shu-Rui Zhang, Jian-Min Wang, Luis C. Ho, Ye-Fei Yuan
Summary: White dwarfs (WDs) in active galactic nucleus (AGN) discs can migrate to the inner radii of the discs and form restricted three-body systems with two WDs moving around the central supermassive black hole (SMBH) in close orbits. These systems can be dynamically unstable, leading to close encounters or collisions. N-body simulations are used to study the evolution of such systems with different initial orbital separation, relative orbital inclination, and SMBH mass. The event rate of cosmic WD-WD collisions in AGN discs is estimated to be about 300 Gpc(-3) yr(-1).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Jincheng Guo, Jingkun Zhao, Huawei Zhang, Jiajun Zhang, Yu Bai, Nikolay Walters, Yong Yang, Jifeng Liu
Summary: This paper reports the identification of white dwarfs in the 5th Data Release of LAMOST, including spectral types and new identifications. Different types of white dwarfs were classified and candidates were selected using machine learning methods, with parameters estimated and mass distribution peaks found. The data and methods used for selecting WD candidates for the second phase of the LAMOST survey are also addressed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. S. Hernandez, M. R. Schreiber, S. G. Parsons, B. T. Gansicke, O. Toloza, G. Tovmassian, M. Zorotovic, F. Lagos, R. Raddi, A. Rebassa-Mansergas, J. J. Ren, C. Tappert
Summary: Establishing a large sample of post-common-envelope binaries (PCEBs) that consist of a white dwarf plus an intermediate mass companion star of spectral type AFGK, offers the potential to provide new constraints on theoretical models of white dwarf binary formation and evolution. Two new systems, TYC 110-755-1 and TYC 3858-1215-1, have been analyzed in detail in this study. The orbital periods of the two systems were found to be similar to 0.85 and similar to 1.64 d, respectively. The mass of the white dwarf in TYC 110-755-1 was measured to be 0.78 M-circle dot using HST spectroscopy. TESS high-time-resolution photometry revealed that both secondary stars were magnetically extremely active.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. S. Hernandez, M. R. Schreiber, S. G. Parsons, B. T. Gansicke, F. Lagos, R. Raddi, O. Toloza, G. Tovmassian, M. Zorotovic, P. Irawati, E. Pasten, A. Rebassa-Mansergas, J. J. Ren, P. Rittipruk, C. Tappert
Summary: Constraints from surveys of post-common envelope binaries have led to significant progress in understanding the formation of close white dwarf binary stars with low-mass companions. The study extends to larger secondary masses and predicts diverse evolutionary futures for the three systems with G-type secondary stars. Despite similarities in orbital period and spectral type, the systems show varied outcomes in their evolutionary paths.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Tilemachos M. Athanasiadis, Marina Berezina, John Antoniadis, David J. Champion, Marilyn Cruces, Laura Spitler, Michael Kramer
Summary: A search for pulsars at the positions of multiple white dwarfs did not yield significant pulsar signals, indicating a low fraction of neutron stars (NSs) orbiting these white dwarfs. This result is important for targeted surveys aimed at discovering millisecond pulsars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
S. O. Kepler, Detlev Koester, Ingrid Pelisoli, Alejandra D. Romero, Gustavo Ourique
Summary: White dwarfs represent the final evolutionary stage for over 97% of all stars and can provide valuable insights into the structure and evolution of the Galaxy. By analyzing new spectra from the Sloan Digital Sky Survey Data Release 16, researchers identified and classified 2410 stars, including 1404 DA stars, 189 DZ stars, and others. They also reported atmospheric parameters and masses for a subset of stars with high signal-to-noise ratios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
F. Lagos, M. R. Schreiber, M. Zorotovic, B. T. Gansicke, M. P. Ronco, Adrian S. Hamers
Summary: The study reconstructs the evolutionary history of a giant planet candidate orbiting a white dwarf, proposing common envelope evolution as a likely mechanism for the planet's current position. It suggests that common envelope evolution is a plausible explanation for the system's configuration and is consistent with the total age and membership to the Galactic thin disc.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Samuel Pearson, Aleks Scholz, Paula S. Teixeira, Koraljka Muzic, Victor Almendros-Abad
Summary: Based on spectroscopic observations of 68 candidates in NGC 2264, researchers confirmed 13 brown dwarfs and 19 M-type stars, with ages predominantly younger than the known cluster population, indicating distinct formation processes. The estimated total of 200-600 brown dwarfs in NGC 2264 suggests a star-to-brown dwarf ratio between 2.5:1 and 7.5:1, with a consistent substellar mass function slope of alpha = 0.43(-0.56)(+0.41) across various young clusters, indicating a uniformity in substellar mass functions within star-forming environments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jenni R. French, Sarah L. Casewell, Trent J. Dupuy, John H. Debes, Elena Manjavacas, Emily C. Martin, Siyi Xu
Summary: We confirm SDSS J222551.65+001637.7AB as a closely separated, resolved white dwarf-brown dwarf binary. The binary consists of a white dwarf with a temperature of 10926 +/- 246 K and a brown dwarf companion of L4 spectral type, separated by 0.9498 +/- 0.0022 arcsec. The age of the binary is estimated to be 1.97(-0.76)(+4.41) Gyr. This binary is likely a member of the thick disc and is the third closest spatially resolved white dwarf-brown dwarf binary known.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Pascal M. Keller, Elme Breedt, Simon Hodgkin, Vasily Belokurov, James Wild, Ignacio Garcia-Soriano, Jacob L. Wise
Summary: Using the largest ever catalogue of white dwarf stars provided by Gaia and the third public data release of the Zwicky Transient Facility (ZTF), researchers have identified 18 new eclipsing white dwarf binaries. The method used exploits light-curve statistics and the box least-squares algorithm to detect periodic light-curve variability. The majority of these white dwarfs have MS companions according to their position in the Gaia H-R diagram. Spectroscopy for 17 of the binaries has also been provided.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Heidi B. Thiemann, Andrew J. Norton, Hugh J. Dickinson, Adam McMaster, Ulrich C. Kolb
Summary: The SuperWASP variable stars Zooniverse project has provided valuable data for studying stellar variables, with volunteer-classified light curves having a high accuracy rate of 89% for detached and semidetached eclipsing binaries, but only 9% for rotationally modulated variables. The project has identified unique and extreme variables, such as long-period contact binaries and previously unknown binaries and pulsators, and is developing a web portal for researchers to access the project's outputs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
M. Dorsch, N. Reindl, I Pelisoli, U. Heber, S. Geier, A. G. Istrate, S. Justham
Summary: This paper reports the discovery of a strongly magnetic helium-rich hot subdwarf star (He-sdO) and presents the first spectroscopic analysis of any magnetic hot subdwarf. The study provides overwhelming evidence for the double-degenerate merger scenario based on the determined atmospheric parameters, metal abundances, and strong magnetic field.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
G. Moesenlechner, E. Paunzen, I Pelisoli, J. Seelig, S. Stidl, H. M. Maitzen
Summary: This study focuses on the evolutionary status and stellar model input of spectroscopic sdA stars by analyzing pulsations and binarity. The results show that 13 out of 25 targets exhibit various types of variability.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Alejandra D. Romero, S. O. Kepler, J. J. Hermes, Larissa Antunes Amaral, Murat Uzundag, Zsofia Bognar, Keaton J. Bell, Madison VanWyngarden, Andy Baran, Ingrid Pelisoli, Gabriela da Rosa Oliveira, Detlev Koester, T. S. Klippel, Luciano Fraga, Paul A. Bradley, Tyler M. Heintz, Joshua S. Reding, B. C. Kaiser, Stephane Charpinet
Summary: We report the discovery of 74 new pulsating DA white dwarf stars, or ZZ Cetis, from the data obtained by the Transiting Exoplanet Survey Satellite mission. By analyzing the period spectra and performing an asteroseismological analysis, the researchers estimated the structure parameters of the sample, including stellar mass, effective temperature, and hydrogen envelope mass. The findings have significant implications for the study of white dwarfs and stellar evolution theory.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
S. Sanjayan, A. S. Baran, J. Ostrowski, P. Nemeth, I Pelisoli, R. Ostensen, J. W. Kern, M. D. Reed, S. K. Sahoo
Summary: Results of the analysis show that only three sdB stars in the open cluster NGC 6791 are pulsating, with hints of radial velocity variability suggesting some of them may be in binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. Culpan, S. Geier, N. Reindl, I Pelisoli, N. Gentile Fusillo, A. Vorontseva
Summary: Based on the ongoing spectroscopic surveys and Gaia EDR3 data, this study compiled new releases of two catalogues of hot subluminous stars. The new catalogues provide more observational sources, improved accuracy in astrometry, and refined selection functions, particularly in crowded regions of the Galactic plane and towards the Magellanic Clouds.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
S. Geier, M. Dorsch, I Pelisoli, N. Reindl, U. Heber, A. Irrgang
Summary: Hot subdwarf stars are likely formed by close binary interactions and represent a late stage in the evolution of low-mass stars. A study of radial velocity variability reveals completely different behavior between He-poor and He-rich hot subdwarfs. There is likely no evolutionary connection between these subtypes, and the majority of hot subdwarf stars are formed through binary merger channels.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
H. Xiong, L. Casagrande, X. Chen, J. Vos, X. Zhang, S. Justham, J. Li, T. Wu, Y. Li, Z. Han
Summary: Blue large-amplitude pulsators (BLAPs) are a newly discovered and extremely rare type of variable star. Their origins and internal structures have attracted a great deal of attention. This study uses MESA models to explore whether shell helium-burning subdwarfs type B (SHeB sdBs) can explain the properties of BLAPs. The models that best match existing observational constraints have helium core masses in the range of 0.45-0.5 solar masses and predict a possible change from positive to negative rate of period change. Binary evolution is a potential formation channel for SHeB sdBs.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Zhenxin Lei, Ruijie He, Peter Nemeth, Joris Vos, Xuan Zou, Ke Hu, Huaping Xiao, Huahui Yan, Jingkun Zhao
Summary: A total of 222 hot subdwarf stars were identified with LAMOST DR8 spectra, among which 131 stars show composite spectra and have been decomposed, while 91 stars present single-lined spectra. Two long-period composite sdB binaries were newly discovered, one of which has the highest eccentricity among known wide sdB binaries. 15 composite sdB stars in the high-probability binary region of the RUWE-AEN plane deserve priority follow-up observations to further study their binary nature. A distinct gap is observed among the temperatures of cool companions in the composite-spectrum sample.
ASTROPHYSICAL JOURNAL
(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
James Munday, T. R. Marsh, Mark Hollands, Ingrid Pelisoli, Danny Steeghs, Pasi Hakala, Elme Breedt, Alex Brown, V. S. Dhillon, Martin J. Dyer, Matthew Green, Paul Kerry, S. P. Littlefair, Steven G. Parsons, Dave Sahman, Sorawit Somjit, Boonchoo Sukaum, James Wild
Summary: The shortest-period binary star system known as RX J0806.3+1527 (HM Cancri) has been observed optically for more than two decades. It was unexpected that its orbital frequency is currently increasing due to gravitational wave radiation since the mass donor was expected to expand on mass loss, leading to a decreasing orbital frequency. However, our measurements show that the frequency is negative, indicating that mass transfer is counteracting orbital decay and the system will reverse within 2100 +/- 800 years. Our findings support the belief that HM Cancri is still one of the brightest verification binaries for the Laser Interferometer Space Antenna spacecraft.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Schwope, T. R. Marsh, A. Standke, I. Pelisoli, S. Potter, D. Buckley, J. Munday, V. Dhillon
Summary: We observed the X-ray emission of a newly discovered pulsating white dwarf using SRG/eROSITA and XMM-Newton. The source was initially found during the eROSITA all-sky survey and was confirmed to be a pulsar through simultaneous X-ray and ultraviolet pulsations. The X-ray spectrum and variability suggest residual accretion, distinguishing it from the prototypical white-dwarf pulsar.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Alex J. Brown, Steven G. Parsons, Jan van Roestel, Alberto Rebassa-Mansergas, Elme Breedt, Vik S. Dhillon, Martin J. Dyer, Matthew J. Green, Paul Kerry, Stuart P. Littlefair, Thomas R. Marsh, James Munday, Ingrid Pelisoli, David Sahman, James F. Wild
Summary: Wide-field time-domain photometric sky surveys have discovered a large number of eclipsing white dwarf plus M dwarf binaries, providing valuable information and insights into astrophysics. Precise follow-up observations are crucial to fully understand and utilize these systems. In this study, we present the first results of a high-speed multiband photometric follow-up program, which allows us to measure temperatures, masses, and radii of the components with improved precision. We also made interesting discoveries, such as sub-stellar secondaries and strongly magnetic white dwarfs. Additionally, we found the first pulsating white dwarfs in detached and eclipsing post-common-envelope binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ingrid Pelisoli, T. R. Marsh, David A. H. Buckley, I. Heywood, Stephen. B. Potter, Axel Schwope, Jaco Brink, Annie Standke, P. A. Woudt, S. G. Parsons, M. J. Green, S. O. Kepler, James Munday, A. D. Romero, E. Breedt, A. J. Brown, V. S. Dhillon, M. J. Dyer, P. Kerry, S. P. Littlefair, D. I. Sahman, J. F. Wild
Summary: White dwarf stars are common and often found in binaries, providing important insights into binary formation and evolution. The two remarkable systems, AR Scorpii and J191213.72-441045.1, exhibit pulsed emission and challenging theoretical models.
Article
Astronomy & Astrophysics
Nicole Reindl, Ramazan Islami, Klaus Werner, S. O. Kepler, Max Pritzkuleit, Harry Dawson, Matti Dorsch, Alina Istrate, Ingrid Pelisoli, Stephan Geier, Murat Uzundag, Judith Provencal, Stephen Justham
Summary: We report on the spectroscopic confirmation of 68 new bright and blue white dwarfs, which nearly doubles the number of the hottest known white dwarfs. We also discovered new types of white dwarfs and found that a significant fraction of them exhibit photometric variability. These findings are important for understanding the formation and evolution of white dwarfs.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
James Munday, P-E Tremblay, J. J. Hermes, Brad Barlow, Ingrid Pelisoli, T. R. Marsh, Steven G. Parsons, David Jones, S. O. Kepler, Alex Brown, S. P. Littlefair, R. Hegedus, Andrzej Baran, Elme Breedt, V. S. Dhillon, Martin J. Dyer, Matthew J. Green, Mark R. Kennedy, Paul Kerry, Isaac D. Lopez, Alejandra D. Romero, Dave Sahman, Hannah L. Worters
Summary: We discovered an eclipsing double white dwarf binary system with an orbital period of 47.19 minutes. The primary white dwarf in the system has a mass of approximately 0.40 solar masses, while the secondary white dwarf has a mass of around 0.28 solar masses and is also likely to be of type DA. This system is now the third-closest eclipsing double white dwarf binary that has been discovered, with a distance of approximately 400 pc, and it will be detectable by upcoming gravitational wave detectors in the mHz frequency range. The orbital decay of the system can be measured photometrically with a precision of better than 1% within 10 years. The binary is expected to merge in approximately 41 million years, likely forming a single, more massive white dwarf.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)