Article
Astronomy & Astrophysics
Chunhua Zhu, Helei Liu, Zhaojun Wang, Guoliang Lu
Summary: This study investigated the formation of DB WDs and the effects of input parameters on the structures of these WDs. It discussed the impacts of various factors on the element abundances of WD surfaces and compared theoretical models with observations to understand the evolutionary sequence of heavy element abundance on DBZ WD surfaces. Results showed that input parameters had minimal effects on DB WD structures, while mass-accretion rate and effective temperature were key determinants of heavy element abundances on WD surfaces.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
R. E. Ryan, P. Thorman, C. Aganze, A. J. Burgasser, S. H. Cohen, N. P. Hathi, B. Holwerda, N. Pirzkal, R. A. Windhorst
Summary: In this study, a self-consistent model of the Milky Way is presented to reproduce the observed distributions and total velocity dispersion of brown dwarfs. The results suggest that brown dwarfs likely form via similar processes as main-sequence stars. Wide-field infrared imaging or low-resolution spectroscopic surveys are recommended for further refinement of these conclusions.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
G. Guidarelli, J. Nordhaus, J. Carroll-Nellenback, L. Chamanady, A. Frank, E. G. Blackman
Summary: Observations show that many isolated white dwarfs have magnetic fields exceeding a MegaGauss. These magnetic fields are likely formed in interacting binary systems, where the companion star is destroyed, leaving behind a highly magnetized white dwarf. Using hydrodynamical simulations, we studied the tidal disruption of planets and brown dwarfs inside an asymptotic giant branch star, leading to the formation of accretion discs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
F. C. Wachlin, G. Vauclair, S. Vauclair, L. G. Althaus
Summary: A grid of models for hydrogen-rich white dwarfs accreting heavy material was provided in this study. The models considered various effective temperatures, envelope hydrogen contents, and accretion rates. The calculations included relevant physical processes such as thermohaline convection. The results obtained can be used to estimate accretion rates and study evolved planetary systems.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
L. Gehrig, E. Gaidos, M. Guedel
Summary: The rotation periods of young low-mass stars after disks have dissipated but before magnetized winds have removed significant angular momentum is an important starting point for gyrochronology and models of stellar rotational evolution. A recent analysis suggests that the distribution of specific angular momentum (SAM) in these stars is mass-independent, but the underlying physics of this observation is unclear.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
L. Gehrig, E. I. Vorobyov
Summary: Our study shows that additional heat added into the stellar interior, accretion history, and stellar winds have the strongest influence on the spin evolution of low-mass stars during their first million years. Based on these results, we are motivated to combine our model with a hydrodynamic disk evolution code to include important aspects such as episodic accretion events, magnetic disk winds, and photoevaporation.
ASTRONOMY & ASTROPHYSICS
(2023)
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
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
Sophie Dubber, Beth Biller, Katelyn Allers, Jessy Jose, Loic Albert, Blake Pantoja, Clemence Fontanive, Michael Liu, Zhoujian Zhang, Wen-Ping Chen, Bhavana Lalchand, Belinda Damian, Tanvi Sharma
Summary: Using CFHT photometry and IRTF spectroscopy, low-mass candidate members of Serpens South and Serpens Core were identified using the W-band method. Young, low-mass Serpens candidate members were reported with masses less than 0.12 solar masses. Additionally, a binary system was discovered with components separated by approximately 45AU, each with spectral types and masses within a specific range. The analysis also discussed the impact of dust attenuation and reddened background stars on the reliability of the findings.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
L. T. T. Soethe, S. O. Kepler
Summary: The study explores the formation of Extremely low-mass white dwarfs (ELM WDs) in binary systems using the treatment of convection and rotation boosted magnetic braking. By calculating evolutionary sequences, ELM models in the range 0.15-0.27 M-circle dot are obtained from a broad range of initial orbital periods, showing the potential formation of ultracompact X-ray binaries (UCXBs) and wide-orbit binary millisecond pulsars. The relation between mass and orbital period obtained is consistent with observational data from He WD companions to pulsars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Samuel A. Beiler, Katelyn N. Allers, Michael Cushing, Jacqueline Faherty, Mark Marley, Andrew Skemer
Summary: We conducted a spectroscopic study on eight young L dwarfs in the L-band (2.98-3.96 μm) with spectral types ranging from L2 to L7. Our analysis focused on the evolution of the Q-branch of methane absorption feature and the impact of including the L-band data on atmoshperic models. We found that the Q-branch feature first appears between L3 and L6 and that the addition of the L band causes a drop in effective temperature and requires thick clouds and higher vertical mixing rates in the models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
L. Gehrig, D. Steiner, E. Vorobyov, M. Guedel
Summary: The study aims to investigate the influence of hydrodynamic disk evolution on stellar rotational period and vice versa during the accretion phase. By combining the TAPIR disk code with a stellar spin evolution model, the research can reproduce the observed fast and slow rotating stars in young stellar clusters within a defined parameter space.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
E. Gonzalez Egea, R. Raddi, D. Koester, L. K. Rogers, F. Marocco, W. J. Cooper, J. C. Beamin, B. Burningham, A. Day-Jones, J. Forbrich, D. J. Pinfield
Summary: Spectroscopic observations of white dwarfs indicate pollution by exoplanetary material and provide insights into their bulk composition. Analysis of a DA white dwarf with strong infrared excess reveals potential emission from a dusty disc. Detection of Ca, Fe, and Mg absorption lines in two spectra taken 8 years apart suggests accretion from a dusty disc.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
E. Gonzalez Egea, R. Raddi, D. Koester, L. K. Rogers, F. Marocco, W. J. Cooper, J. C. Beamin, B. Burningham, A. Day-Jones, J. Forbrich, D. J. Pinfield
Summary: The spectroscopic observations of white dwarf WDJ181417.84-735459.83 reveal contamination by exoplanetary material, with evidence of accretion from a dusty disc. The infrared excess and emission from a dusty disc were confirmed through spectroscopic and photometric analysis. Absorption lines of Ca, Fe, and Mg were found in two X-SHOOTER spectra taken 8 years apart, indicating consistent accretion from the dusty disc without variability in the absorption lines. Fitting a blackbody model yielded a temperature of 910 +/- 50 K and an estimated total accretion flux from spectroscopic metal lines of vertical bar M vertical bar = 1.784 x 10(9) g s(-1).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
A. Frasca, H. M. J. Boffin, C. F. Manara, J. M. Alcala, P. Abraham, E. Covino, M. Fang, M. Gangi, G. J. Herczeg, A. Kospal, L. Venuti, F. M. Walter, J. Alonso-Santiago, K. Grankin, M. Siwak, E. Alecian, S. Cabrit
Summary: In this study, the close pre-main sequence spectroscopic binary CVSO 104 in Ori OB1 was analyzed, revealing the orbital elements and stellar parameters of the system, as well as a significant infrared excess related to a circumbinary disk. Both components were found to be accreting at a similar level, with excess emission observed in Hα and Hβ possibly connected to accretion structures. The optical companion CVSO 104 B was identified as a background Sun-like star not physically associated with the PMS system.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
D. M. -A. Meyer, E. I. Vorobyov, V. G. Elbakyan, B. Stecklum, J. Eisloeffel, A. M. Sobolev
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
Vardan G. Elbakyan, Eduard I. Vorobyov, Christian Rab, Dominique M. -A. Meyer, Manuel Guedel, Takashi Hosokawa, Harold Yorke
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
Yaroslav Pavlyuchenkov, Vitaly Akimkin, Dmitri Wiebe, Eduard Vorobyov
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
D. M-A Meyer, A. Kreplin, S. Kraus, E. I. Vorobyov, L. Haemmerle, J. Eisloeffel
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
Eduard Vorobyov, Aleksandr M. Skliarevskii, Vardan G. Elbakyan, Yaroslav Pavlyuchenkov, Vitaly Akimkin, Manuel Guedel
ASTRONOMY & ASTROPHYSICS
(2019)
Article
Astronomy & Astrophysics
Eduard Vorobyov, Vardan G. Elbakyan, Hauyu Baobab Liu, Michihiro Takami
Summary: This study investigates three distinct mechanisms that trigger accretion and luminosity bursts, finding that kinematic features of burst-hosting disks can be used to distinguish between the mechanisms and identify the origin of a particular burst. Further studies are needed to constrain the mechanisms behind FU Orionis bursts through a wider model parameter space and the construction of synthetic disk images in thermal dust and molecular line emission.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Kundan Kadam, Eduard Vorobyov, Agnes Kospal
Summary: The research on the effects of low-metallicity environments on the structure and outbursting behavior of protoplanetary disks (PPDs) found that metal-poor disks accumulate more mass in the inner regions, have shorter and more powerful outbursting phases, especially in the early stages of disk evolution. Disks with the lowest metallicity and higher cloud core temperature showed the most significant differences, and outbursts were relatively rare in disks around low-mass stars. The metal content of the disk environment can have profound effects on both the disk structure and evolution in terms of episodic accretion.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Tamara Molyarova, Eduard I. Vorobyov, Vitaly Akimkin, Aleksandr Skliarevskii, Dmitri Wiebe, Manuel Guedel
Summary: The snowlines of volatile species in protoplanetary disks are influenced by changes in gas composition and dust physical properties, leading to complex distribution patterns. As the disk evolves, the snowlines shift closer to the star, with volatile molecules tending to accumulate near these snowlines, forming thick icy mantles potentially important for dust dynamics.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
T. Steindl, K. Zwintz, T. G. Barnes, M. Muellner, E. Vorobyov
Summary: The study aims to constrain the physics of accretion on protostellar seeds by using observed spectroscopic parameters and stellar pulsations. It discovered several previously unknown pulsating pre-main-sequence stars, with evolutionary tracks showing that a mass accretion rate of 5 x 10(-6) M-circle dot yr(-1) provides the best results.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Kundan Kadam, Eduard Vorobyov, Shantanu Basu
Summary: In this study, the formation and evolution of primordial dusty rings in protoplanetary discs are investigated using long-term, coupled dust-gas, magnetohydrodynamic simulations. The simulations show that when considering dust evolution and magnetic field evolution, the dusty rings formed are more numerous and extensive, while the dead zone is more robust and persistent for a longer period of time. These rings contain enough dust mass to become streaming unstable, leading to rapid planetesimal formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Multidisciplinary Sciences
Thomas Steindl, Konstanze Zwintz, Eduard Vorobyov
Summary: The classical concept of stellar evolution suggests that stars forget their early evolutionary history once they reach the main sequence. However, this study shows that the accretion history of stars can leave a detectable imprint on their interior structures, which can be studied using asteroseismology. This finding challenges the traditional understanding of early stellar evolution and opens up new possibilities for investigating the interior structures of young pulsating stars.
NATURE COMMUNICATIONS
(2022)
Article
Astronomy & Astrophysics
Kundan Kadam, Eduard Vorobyov, Zsolt Regaly, Agnes Kospal, Peter Abraham
ASTROPHYSICAL JOURNAL
(2020)
Article
Astronomy & Astrophysics
Kundan Kadam, Eduard Vorobyov, Zsolt Regaly, Agnes Kospal, Peter Abraham
ASTROPHYSICAL JOURNAL
(2019)
Article
Astronomy & Astrophysics
J. A. White, A. Kospal, C. Rab, P. Abraham, F. Cruz-Saenz de Miera, T. Csengeri, O. Feher, R. Guesten, T. Henning, E. Vorobyov, M. Audard, A. Postel
ASTROPHYSICAL JOURNAL
(2019)
Article
Astronomy & Astrophysics
Eiji Akiyama, Eduard Vorobyov, Hauyu Baobabu Liu, Ruobing Dong, Jerome de Leon, Sheng-Yuan Liu, Motohide Tamura
ASTRONOMICAL JOURNAL
(2019)