Instabilities in the yellow hypergiant domain

0586799 - ASÚ 2025 RIV US eng J - Článek v odborném periodiku
Glatzel, W. - Kraus, Michaela
Instabilities in the yellow hypergiant domain.
Monthly Notices of the Royal Astronomical Society. Roč. 529, č. 4 (2024), s. 4947-4957. ISSN 0035-8711. E-ISSN 1365-2966
Grant CEP: GA ČR(CZ) GA20-00150S
GRANT EU: European Commission(XE) 823734 - POEMS
Institucionální podpora: RVO:67985815
Klíčová slova: instabilities * stars atmospheres * massive stars
Obor OECD: Astronomy (including astrophysics,space science)
Impakt faktor: 4.8, rok: 2022
Způsob publikování: Open access

Yellow hypergiants (YHGs) are massive stars that are commonly interpreted to be in a post-red supergiant evolutionary state. These objects can undergo outbursts on time-scales of decades, which are suspected to be due to instabilities in the envelope. To test this conjecture, the stability of envelope models for YHGs with respect to infinitesimal, radial perturbations is investigated. Violent strange mode instabilities with growth rates in the dynamical regime are identified if the luminosity-to-mass ratio exceeds ≈104 in solar units. For the observed parameters of YHGs, we thus predict instability. The strange mode instabilities persist over the entire range of effective temperatures from red to blue supergiants. Due to short thermal time-scales and dominant radiation pressure in the envelopes of YHGs, a non-adiabatic stability analysis is mandatory and an adiabatic analysis being the basis of the common perception is irrelevant. Contrary to the prevailing opinion, the models considered here do not exhibit any adiabatic instability.
Trvalý link: https://hdl.handle.net/11104/0354197