Planets around extreme horizontal branch stars

TL;DR

This paper reviews recent findings on how tidal interactions, multiple planets, and stellar radiation influence the survival and detection of planets around extreme horizontal branch stars.

Contribution

It introduces a new understanding of tidal effects on planetary survival, suggests the presence of multiple planets around sdB/sdO stars, and discusses observational signatures of evaporating substellar objects.

Findings

Enhanced planetary survivability due to tidal interactions before common envelope phase

Multiple planets likely exist around many sdB/sdO stars

Detectable Doppler-shifted Balmer lines from evaporated gas around these stars

Abstract

We review three main results of our recent study: * We show that a proper treatment of the tidal interaction prior to the onset of the common envelope (CE) leads to an enhance mass loss. This might increase the survivability of planets and brown dwarfs that enter a CE phase. * From the distribution of planets around main sequence stars, we conclude that around many sdB/sdO stars more than one planet might be present. One of these might have a close orbit and the others at about orbital periods of years or more. * We show that the intense ionizing flux of the extreme horizontal branch star might evaporate large quantities of a very close surviving substellar object. Balmer emission lines from the evaporated gas can be detected via their Doppler shifts.