Article
Astronomy & Astrophysics
Matthias R. Schreiber, Diogo Belloni, Monica Zorotovic, Sarai Zapata, Boris T. Gansicke, Steven G. Parsons
Summary: The origin of strong magnetic fields in white dwarfs has puzzled scientists for decades. A proposed dynamo mechanism operating in rapidly rotating and crystallizing white dwarfs may explain the occurrence of strong magnetic fields in white dwarfs with low-mass main-sequence star companions. This study investigates whether the same mechanism can produce strong magnetic fields in close double white dwarfs. The findings suggest that a rotation-and crystallization-driven dynamo plays a major role in the generation of strong magnetic fields in white dwarfs, as supported by the incidence of magnetic fields in close double white dwarfs.
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
Alexander Venner, Simon Blouin, Antoine Bedard, Andrew Vanderburg
Summary: The observational signature of core crystallization of white dwarfs has been discovered, but it requires additional mechanisms of energy release in white dwarf interiors. In this work, a newly discovered white dwarf is confirmed to be undergoing crystallization, making it the first one with externally constrained total age. However, the age determination is not precise enough to make strong constraints to models of white dwarf crystallization, but the results support the hypothesis of Ne-22 phase separation causing the excess cooling delay.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Eliot Finch, Giorgia Bartolucci, Daniel Chucherko, Ben G. Patterson, Valeriya Korol, Antoine Klein, Diganta Bandopadhyay, Hannah Middleton, Christopher J. Moore, Alberto Vecchio
Summary: Double white dwarfs (DWDs) are the most common gravitational-wave sources for LISA. Among them, a subset known as verification binaries (VBs) can be guaranteed sources of detectable GWs. We analyzed all currently known VB candidates and found that 25 of them can be detected within a 4 yr observation time. We also explored the potential of GW observations in combination with EM observations and estimated the time to detection for VBs in the early months of LISA operations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Chengyuan Wu, Heran Xiong, Xiaofeng Wang
Summary: Studies suggest that some ultra-massive white dwarfs may have experienced additional cooling delays and may originate from the merger evolution of carbon-oxygen white dwarfs and helium white dwarfs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jiangdan Li, Christopher A. Onken, Christian Wolf, Peter Nemeth, Mike Bessell, Zhenwei Li, Xiaobin Zhang, Jiao Li, Luqian Wang, Lifang Li, Yangping Luo, Hailiang Chen, Kaifan Ji, Xuefei Chen, Zhanwen Han
Summary: A hot subdwarf O (sdO) star and a white dwarf (WD) binary system, which has the capability of emitting low-frequency gravitational waves and possibly being the progenitor of Type Ia supernovae, has been discovered. Spectroscopy and light curve analysis provide information about the system, such as temperature, mass ratio, and disc characteristics. The binary system is believed to have originated from a common envelope ejection channel and might result in an R Coronae Borealis (R CrB) star.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
D. Baroch, J. C. Morales, I Ribas, V. J. S. Bejar, S. Reffert, C. Cardona Guillen, A. Reiners, J. A. Caballero, A. Quirrenbach, P. J. Amado, G. Anglada-Escude, J. Colome, M. Cortes-Contreras, S. Dreizler, D. Galadi-Enriquez, A. P. Hatzes, S. Jeffers, Th Henning, E. Herrero, A. Kaminski, M. Kuerster, M. Lafarga, N. Lodieu, M. J. Lopez-Gonzalez, D. Montes, E. Palle, M. Perger, D. Pollacco, C. Rodriguez-Lopez, E. Rodriguez, A. Rosich, P. Schoefer, A. Schweitzer, Y. Shan, L. Tal-Or, M. Zechmeister
Summary: During the CARMENES survey, nine multiple stellar systems were studied, with the results showing the detection of several new systems with long periods and low radial-velocity amplitudes. The study derived radial velocities of the stars using cross-correlation techniques and template matching, combining data from various sources to improve analysis. The significant findings included the determination of spectroscopic orbits of nine systems, with insights into potential brown dwarfs and white dwarfs in close binary orbits.
ASTRONOMY & ASTROPHYSICS
(2021)
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)
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
Peter Scherbak, Jim Fuller
Summary: This study estimates the CE energy efficiency alpha(CE) needed to unbind the hydrogen envelope through reverse modeling of white dwarf (WD) binaries, finding that alpha(CE) around 0.2-0.4 is consistent with each system studied. By mapping WD models to a grid of red giant progenitor stars, the total envelope binding energies and possible orbital periods at the point CE evolution is initiated are determined, thus constraining alpha(CE) for CE events that produce He-core WDs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Kosakowski, M. Kilic, W. R. Brown, P. Bergeron, T. Kupfer
Summary: The study presents the discovery of nine deeply eclipsing white dwarf candidates in the ZTF data, four of which were further investigated. Three systems were found to exhibit total eclipses in both ZTF and follow-up observations. It was revealed that all four systems contain a white dwarf with low-mass stellar companions. Additionally, the study identified 41 additional eclipsing WD+M candidates, including two new candidate short-period white dwarf-brown dwarf binaries.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. Irrgang, S. Geier, U. Heber, T. Kupfer, K. El-Badry, S. Bloemen
Summary: Originally classified as a BHB star, SDSS J160429.12+100002.2 was thought to be a hypervelocity star pointing towards Earth, but further analysis revealed it to be a spectroscopic binary system with a less luminous B-type star. Its chemical composition displays a unique pattern possibly caused by atomic diffusion processes, and the visible component is believed to be an unevolved white dwarf.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Wenshi Tang, Xiang-Dong Li
Summary: This study investigates the impact of pulsar high-energy radiation on the cooling of helium white dwarfs (He WDs), finding that evaporative wind mass-loss driven by radiation may accelerate WD cooling. Standard WD cooling can reproduce temperatures for relatively hot He WDs, while evaporation might be required for relatively cool He WDs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hang Yu, Jim Fuller, Kevin B. Burdge
Summary: We find that dynamical tides can significantly affect flux in hot white dwarfs, especially at longer orbital periods. The ratio of flux modulation due to dynamical tides and equilibrium tides increases as the white dwarf's radius decreases.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
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
Alekzander Kosakowski, Mukremin Kilic, Warren Brown
Summary: The study utilized observations from the Apache Point Observatory and Gemini telescope to analyze the SDSS J082239.54+304857.19 binary system, revealing a low-mass DA white dwarf and a companion star. The research indicates that the temperature of the secondary star in the system is approximately 5200K, and a significant measurement of orbital decay due to gravitational waves is expected to be possible in 2023.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Scott J. Kenyon, Benjamin C. Bromley
Summary: Based on numerical calculations, the long-term evolution of circumbinary debris from the Pluto-Charon giant impact is studied. Most solids are ejected from the system due to dynamical interactions with Pluto and Charon over timescales of 100-1000 yr. The resulting circumbinary disk in the Pluto-Charon orbital plane is more extended compared to narrow rings produced from other collision debris, but may be less suitable for producing small circumbinary satellites.
ASTRONOMICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Joan R. Najita, Scott J. Kenyon, Benjamin C. Bromley
Summary: This study explores the potential connection between protoplanetary disk rings, planets, and debris disks through new calculations, which suggest that solid rings with high initial masses and modest planetesimal formation efficiencies may evolve into known cold debris disks. These findings support the possibility that large protoplanetary disk rings evolve into cold debris disks.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
George W. King, Peter J. Wheatley, Victoria A. Fawcett, Nicola J. Miller, Lia R. Corrales, Marcel A. Agueros
Summary: We present an analysis of XMM-Newton observations of four stars in the young open cluster Praesepe. The planets hosted by these stars are close to the radius-period valley and/or the Neptunian desert, which may be influenced by photoevaporation from X-ray and extreme ultraviolet photons. We compare the XMM-Newton light curves to those measured with K2 at optical wavelengths and find correlated variability between the X-ray and optical light curves. Additionally, simulations show that the envelope of three out of the four planets may be completely stripped due to photoevaporation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Scott J. Kenyon, Benjamin C. Bromley
Summary: The study discusses 500 numerical n-body calculations aimed at constraining the masses and bulk densities of four Pluto's moons. Comparisons favor methods based on the theory of Lee & Peale and suggest that Styx and Kerberos may have bulk densities comparable with water ice.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Jeff J. Andrews, Jason L. Curtis, Julio Chaname, Marcel A. Agueros, Simon C. Schuler, Marina Kounkel, Kevin R. Covey
Summary: The application of clustering algorithms to the Gaia catalog has transformed our understanding of stellar structures in the local Milky Way. The discovery of low-density stellar streams, such as Theia 456, suggests that these structures may be widespread. By analyzing Theia 456 with additional data, we establish its characteristics and comment on the implications for star formation in the Galaxy.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Francys Anthony, Alejandro Nunez, Marcel A. Agueros, Jason L. Curtis, J-D do Nascimento Jr, Joao M. Machado, Andrew W. Mann, Elisabeth R. Newton, Rayna Rampalli, Pa Chia Thao, Mackenna L. Wood
Summary: This study investigates the evolution of magnetism in late-type dwarfs and finds that late-type M dwarfs remain active for longer periods of time. The study also explores the relationship between rotation periods and magnetic activity.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Alejandro Nunez, Marcel A. Agueros, Kevin R. Covey, Stephanie T. Douglas, Jeremy J. Drake, Rayna Rampalli, Emily C. Bowsher, Phillip A. Cargile, Adam L. Kraus, Nicholas M. Law
Summary: X-ray observations of low-mass stars in open clusters provide essential insights into the dependence of magnetic activity on stellar properties and their evolution. This study presents an updated analysis of the rotation-X-ray activity relation in the Praesepe and Hyades clusters, based on updated membership catalogs and collected X-ray detections. The results reveal important findings regarding the saturation of X-ray activity, the relation between Rossby number and X-ray luminosity, and the coronal parameters of binary and single cluster members.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Tyler Richey-Yowell, Evgenya L. Shkolnik, R. O. Parke Loyd, James A. G. Jackman, Adam C. Schneider, Marcel A. Agueros, Travis Barman, Victoria S. Meadows, Rose Gibson, Stephanie T. Douglas
Summary: Observations of 39 K stars show that their UV flux remains constant beyond 650 Myr before falling off significantly by field age, which is different from early M stars. This difference may be due to the spin-down stalling effect reported for K dwarfs. This implies that exoplanets orbiting K dwarfs may experience a stronger UV environment, weakening the case for K stars as hosts of potential super-habitable planets.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Laura Flagg, Christopher M. Johns-Krull, Kevin France, Gregory Herczeg, Joan Najita, Allison Youngblood, Adolfo Carvalho, John Carptenter, Scott J. Kenyon, Elisabeth Newton, Keighley Rockcliffe
Summary: Molecular hydrogen, which is abundant in the galaxy, plays vital roles in planets, their circumstellar environments, and host stars. In this study, the presence of molecular hydrogen in the AU Mic system is confirmed through high-resolution FUV spectra. The gas temperature is estimated to be 1000-2000K, and the emission is likely produced in the star instead of the disk or the planet.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Benjamin C. Bromley, Scott J. Kenyon
Summary: The magnetic field of a host star can affect the orbit of its stellar partner, planet, or asteroid if the orbiting body is magnetic or electrically conducting. When an orbiting permanent magnet is close to the stellar host, it will be drawn towards it due to the dipole-dipole interaction. Although the observed magnetic fields in systems are generally too weak to cause a merger event, they may be strong enough in some compact binaries to result in measurable orbital precession. When the orbiting body is a conductor, the stellar field induces a time-varying magnetic dipole moment, which can lead to eccentricity pumping and resonance trapping. The challenge is that the orbiting body must be close to the star, competing with tidal forces and intense stellar radiation.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Laia Casamiquela, Marwan Gebran, Marcel A. Agueeros, Herve Bouy, Caroline Soubiran
Summary: The recently rediscovered open cluster Stock 2 has the potential to be a testbed for stellar evolution. By conducting a spectroscopic campaign, researchers have identified nine chemically peculiar A stars in the cluster, which can serve as benchmarks for evolutionary models.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Andrew W. Mayo, Courtney D. Dressing, Andrew Vanderburg, Charles D. Fortenbach, Florian Lienhard, Luca Malavolta, Annelies Mortier, Alejandro Nunez, Tyler Richey-Yowell, Emma V. Turtelboom, Aldo S. Bonomo, David W. Latham, Mercedes Lopez-Morales, Evgenya Shkolnik, Alessandro Sozzetti, Marcel A. Agueros, Luca Borsato, David Charbonneau, Rosario Cosentino, Stephanie T. Douglas, Xavier Dumusque, Adriano Ghedina, Rose Gibson, Valentina Granata, Avet Harutyunyan, R. D. Haywood, Gaia Lacedelli, Vania Lorenzi, Antonio Magazzu, A. F. Martinez Fiorenzano, Giuseppina Micela, Emilio Molinari, Marco Montalto, Domenico Nardiello, Valerio Nascimbeni, Isabella Pagano, Giampaolo Piotto, Lorenzo Pino, Ennio Poretti, Gaetano Scandariato, Stephane Udry, Lars A. Buchhave
Summary: K2-136 is a late-K dwarf in the Hyades open cluster with three known, transiting planets. Through analysis of K2 photometry, the periods and radii of the planets are determined. Further analysis using radial velocity measurements provides mass estimates for the planets.
ASTRONOMICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Joan R. Najita, Scott J. Kenyon
Summary: The formation of terrestrial planets like Earth through late-stage giant impacts may not produce the anticipated visible signpost of warm dusty debris due to transport mechanisms that can erase the debris signature. The regeneration of a tenuous gas disk or the powerful stellar wind can effectively remove the warm debris. This suggests that terrestrial planets may quietly assemble without attracting much attention or undergo early formation without late-stage giant impacts.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Alekzander Kosakowski, Warren R. R. Brown, Mukremin Kilic, Thomas Kupfer, Antoine Bedard, A. Gianninas, Marcel A. Agueros, Manuel Barrientos
Summary: We conducted a spectroscopic survey of low-mass white dwarf binaries in the southern sky and identified 28 new binaries, including 19 extremely low-mass white dwarfs and two potential LISA binaries. Our observations revealed periodic photometric variability in TESS and ZTF data, and we provided orbital and atmospheric parameters for each binary. By expanding the sample of ELM Survey binaries in the southern sky, our study contributes to a more comprehensive understanding of these systems.
ASTROPHYSICAL JOURNAL
(2023)
