Substellar companions and the formation of hot subdwarf stars

TL;DR

This paper reviews observational evidence for close substellar companions to hot subdwarf stars and discusses their potential role in triggering the mass loss necessary for the formation of these stars, highlighting key systems like SDSS J0820+0008.

Contribution

It presents the first compelling evidence that substellar objects in close orbits can induce the mass loss needed for hot subdwarf formation, supported by observations of specific systems.

Findings

Detection of substellar companions via spectroscopy and transits.

Eclipsing system SDSS J0820+0008 as key evidence.

Multiple candidate systems identified.

Abstract

We give a brief review over the observational evidence for close substellar companions to hot subdwarf stars. The formation of these core helium-burning objects requires huge mass loss of their red giant progenitors. It has been suggested that besides stellar companions substellar objects in close orbits may be able to trigger this mass loss. Such objects can be easily detected around hot subdwarf stars by medium or high resolution spectroscopy with an RV accuracy at the km/s-level. Eclipsing systems of HW Vir type stick out of transit surveys because of their characteristic light curves. The best evidence that substellar objects in close orbits around sdBs exist and that they are able to trigger the required mass loss is provided by the eclipsing system SDSS J0820+0008, which was found in the course of the MUCHFUSS project. Furthermore, several candidate systems have been discovered.