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Looking into the cradle of the grave: J22564-5910, a potential young post-merger hot subdwarf

Vos, Joris ; Pelisoli, Ingrid ; Budaj, Jan ; Reindl, Nicole ; Schaffenroth, Veronica ; Bobrick, Alexey LU orcid ; Geier, Stephan ; Hermes, J.J. ; Nemeth, Peter and Østensen, Roy , et al. (2021) In Astronomy & Astrophysics 655.
Abstract
Context. We present the discovery of J22564-5910, a new type of hot subdwarf (sdB) which shows evidence of gas present in the
system and it has shallow, multi-peaked hydrogen and helium lines which vary in shape over time. All observational evidence points
towards J22564-5910 being observed very shortly after the merger phase that formed it.

Aims. Using high-resolution, high signal-to-noise spectroscopy, combined with multi-band photometry, Gaia astrometry, and TESS
light curves, we aim to interpret these unusual spectral features.

Methods. The photometry, spectra, and light curves were all analysed, and their results were combined in order to support our
interpretation of the observations: the likely... (More)
Context. We present the discovery of J22564-5910, a new type of hot subdwarf (sdB) which shows evidence of gas present in the
system and it has shallow, multi-peaked hydrogen and helium lines which vary in shape over time. All observational evidence points
towards J22564-5910 being observed very shortly after the merger phase that formed it.

Aims. Using high-resolution, high signal-to-noise spectroscopy, combined with multi-band photometry, Gaia astrometry, and TESS
light curves, we aim to interpret these unusual spectral features.

Methods. The photometry, spectra, and light curves were all analysed, and their results were combined in order to support our
interpretation of the observations: the likely presence of a magnetic field combined with gas features around the sdB. Based on
the triple-peaked H lines, the magnetic field strength was estimated and, by using the shellspec code, qualitative models of gas
configurations were fitted to the observations.

Results. All observations can either be explained by a magnetic field of ∼650 kG, which enables the formation of a centrifugal
magnetosphere, or a non-magnetic hot subdwarf surrounded by a circumstellar gas disc or torus. Both scenarios are not mutually
exclusive and both can be explained by a recent merger.

Conclusions. J22564-5910 is the first object of its kind. It is a rapidly spinning sdB with gas still present in the system. It is the
first post-merger star observed this early after the merger event, and as such it is very valuable system to test merger theories. If the
magnetic field can be confirmed, it is not only the first magnetic sdB, but it hosts the strongest magnetic field ever found in a pre-white
dwarf object. Thus, it could represent the long sought-after immediate ancestor of strongly magnetic white dwarfs. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Stars: binaries, Stars: circumstellar matter, Stars: evolution, Stars: magnetic field, Stars: subdwarfs
in
Astronomy & Astrophysics
volume
655
article number
A43
publisher
EDP Sciences
external identifiers
  • scopus:85119498257
ISSN
1432-0746
DOI
10.1051/0004-6361/202140391
language
English
LU publication?
yes
id
5c37b9e0-8e14-4338-bb55-54218c027899
alternative location
https://arxiv.org/abs/2106.03363
date added to LUP
2021-08-28 14:21:22
date last changed
2024-04-20 11:16:15
@article{5c37b9e0-8e14-4338-bb55-54218c027899,
  abstract     = {{Context. We present the discovery of J22564-5910, a new type of hot subdwarf (sdB) which shows evidence of gas present in the<br/>system and it has shallow, multi-peaked hydrogen and helium lines which vary in shape over time. All observational evidence points<br/>towards J22564-5910 being observed very shortly after the merger phase that formed it.<br/><br/>Aims. Using high-resolution, high signal-to-noise spectroscopy, combined with multi-band photometry, Gaia astrometry, and TESS<br/>light curves, we aim to interpret these unusual spectral features.<br/><br/>Methods. The photometry, spectra, and light curves were all analysed, and their results were combined in order to support our<br/>interpretation of the observations: the likely presence of a magnetic field combined with gas features around the sdB. Based on<br/>the triple-peaked H lines, the magnetic field strength was estimated and, by using the shellspec code, qualitative models of gas<br/>configurations were fitted to the observations.<br/><br/>Results. All observations can either be explained by a magnetic field of ∼650 kG, which enables the formation of a centrifugal<br/>magnetosphere, or a non-magnetic hot subdwarf surrounded by a circumstellar gas disc or torus. Both scenarios are not mutually<br/>exclusive and both can be explained by a recent merger.<br/><br/>Conclusions. J22564-5910 is the first object of its kind. It is a rapidly spinning sdB with gas still present in the system. It is the<br/>first post-merger star observed this early after the merger event, and as such it is very valuable system to test merger theories. If the<br/>magnetic field can be confirmed, it is not only the first magnetic sdB, but it hosts the strongest magnetic field ever found in a pre-white<br/>dwarf object. Thus, it could represent the long sought-after immediate ancestor of strongly magnetic white dwarfs.}},
  author       = {{Vos, Joris and Pelisoli, Ingrid and Budaj, Jan and Reindl, Nicole and Schaffenroth, Veronica and Bobrick, Alexey and Geier, Stephan and Hermes, J.J. and Nemeth, Peter and Østensen, Roy and Reding, Joshua and Uzundag, Murat and Vuckovic, Maja}},
  issn         = {{1432-0746}},
  keywords     = {{Stars: binaries; Stars: circumstellar matter; Stars: evolution; Stars: magnetic field; Stars: subdwarfs}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy & Astrophysics}},
  title        = {{Looking into the cradle of the grave: J22564-5910, a potential young post-merger hot subdwarf}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202140391}},
  doi          = {{10.1051/0004-6361/202140391}},
  volume       = {{655}},
  year         = {{2021}},
}