Hot subdwarfs - Small stars marking important events in stellar evolution

Abstract

Hot subdwarfs are considered to be the compact helium cores of red giants, which lost almost their entire hydrogen envelope. What causes this enormous mass loss is still unclear. Binary interactions are invoked and a significant fraction of the hot subdwarf population is indeed found in close binaries. In a large project we search for the close binary sdBs with the most and the least massive companions. Significantly enhancing the known sample of close binary sdBs we performed the first comprehensive study of this population. Triggered by the discovery of two sdB binaries with close brown dwarf companions in the course of this project, we were able to show that the interaction of stars with substellar companions is an important channel to form sdB stars. Finally, we discovered a unique and very compact binary system consisting of an sdB and a massive white dwarf, which qualifies as progenitor candidate for a supernova type Ia. In addition to that, we could connect those explosions to the class of hypervelocity hot subdwarf stars, which we consider as the surviving companions of such events. Being the stripped cores of red giants, hot subdwarfs turned out to be important markers of peculiar events in stellar evolution ranging all the way from star-planet interactions to the progenitors of stellar explosions used to measure the expansion of our Universe.

10 pages, to appear in Reviews in Modern Astronomy 27, special issue of Astronomical Notes

References in corpus (15)

• Double-detonation sub-Chandrasekhar supernovae: can minimum helium shell masses detonate the core?
• Survival of a brown dwarf after engulfment by a red giant star
• A selection of hot subluminous stars in the GALEX survey II. Subdwarf atmospheric parameters
• Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
• The fastest unbound star in our Galaxy ejected by a thermonuclear supernova
• The hot subdwarf B + white dwarf binary KPD 1930+2752 - a Supernova Type Ia progenitor candidate
• Hot subdwarf binaries from the MUCHFUSS project - Analysis of 12 new systems and a study of the short-period binary population
• On type Ia supernovae and the formation of single low-mass white dwarfs
• An ultra-massive fast-spinning white dwarf in a peculiar binary system
• The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project
• The orbits of subdwarf B + main-sequence binaries. I: The sdB+G0 system PG 1104+243
• KIC7668647: a 14 day beaming sdB+WD binary with a pulsating subdwarf
• Kepler detection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC10001893
• Common Envelope Mergers: A Possible Channel for Forming Single sdB Stars
• Two candidate brown dwarf companions around core helium-burning stars

Cited by in corpus (4)

• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators
• Physical Properties of 29 sdB+dM Eclipsing Binaries in Zwicky Transient Facility
• Follow-up observations of X-ray emitting hot subdwarf star: the He-rich sdO BD +37° 1977