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Open Astronomy

formerly Baltic Astronomy

Editor-in-Chief: Barbuy, Beatriz

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Volume 26, Issue 1

Issues

ε-mechanism driven pulsations in hot subdwarf stars with mixed H-He atmospheres

Tiara Battich
  • Corresponding author
  • Instituto de Astrofísica de La Plata (CONICET-UNLP), Facultad de Ciencias Astronómicas y Geofísicas (UNLP), Buenos Aires , Argentina
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Marcelo M. Miller Bertolami
  • Instituto de Astrofísica de La Plata (CONICET-UNLP) Facultad de Ciencias Astronómicas y Geofísicas (UNLP), Buenos Aires, Argentina
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Alejandro H. Córsico
  • Instituto de Astrofísica de La Plata (CONICETUNLP), Facultad de Ciencias Astronómicas y Geofísicas (UNLP), Buenos Aires, Argentina
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Leandro G. Althaus
  • Instituto de Astrofísica de La Plata (CONICETUNLP), Facultad de Ciencias Astronómicas y Geofísicas (UNLP), Buenos Aires, Argentina
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2017-12-29 | DOI: https://doi.org/10.1515/astro-2017-0431

Abstract

The ε mechanism is a self-excitation mechanism of stellar pulsations which acts in regions where nuclear burning takes place. It has been shown that the ε mechanism can excite pulsations in hot pre-horizontal branch stars before they settle into the stable helium core-burning phase and that the shortest periods of LS IV-14º116 could be explained that way.We aim to study the ε mechanism in stellar models appropriate for hot pre-horizontal branch stars to predict their pulsational properties.We perform detailed computations of non-adiabatic non-radial pulsations on such stellar models.We predict a new instability domain of long-period gravity modes in the log g − log Teff plane at roughly 22000 K ≲ Teff ≲ 50000 K and 4.67 ≲ log g ≲ 6.15, with a period range from ~ 200 to ~ 2000 s. Comparison with the three known pulsating He-rich subdwarfs shows that the ε mechanism can excite pulsations in models with similar surface properties except for modes with the shortest observed periods. Based on simple estimates we expect at least 3 stars in the current samples of hot-subdwarf stars to be pulsating by the ε mechanism. Our results could constitute a theoretical basis for future searches of pulsators in the Galactic field.

Keywords: low-mass stars; stellar oscillations; horizontal-branch stars

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About the article

Received: 2017-09-30

Accepted: 2017-10-20

Published Online: 2017-12-29

Published in Print: 2017-12-20


Citation Information: Open Astronomy, Volume 26, Issue 1, Pages 152–159, ISSN (Online) 2543-6376, DOI: https://doi.org/10.1515/astro-2017-0431.

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