Institute of Astronomy

Naked He-burning Stars: the Physics of the Stripping Mechanism and their UV Properties

SpeakerTalk DateTalk Series
Ylva Götberg25 July 2016Binary Stars Talks

Abstract

Naked helium burning stars, i.e., stars stripped from their hydrogen envelope by a companion, represent the first long-lived post-interaction phase that almost all binaries go through. This is the first step in most of the complex scenarios that eventually give rise to a variety of exotic phenomena, such as X-ray binaries, Ib/c supernovae and double compact objects as sources of gravitational waves. They have also been suggested to be important as sources of ionising photons, but tailored atmosphere models have not been available so far.

We conduct an systematic computational study of the nature of these stripped stars using MESA. With the non-LTE, radiative transfer code CMFGEN we create the first extensive grid of tailored atmosphere models. This allows us for the first time to make reliable estimates for the expected UV spectra which we compare with observed systems such as the quasi WR in HD45166. We further study the effects of metallicity, mass loss and initial binary parameters to understand the physics of the envelope stripping mechanism. 

We quantify the ionising flux and conclude that stripped stars are not only important sources of hydrogen ionising radiation, but potentially also important sources of helium ionising radiation. We discuss how these computations can guide future observing campaigns to systematically search for stripped stars. Our results will be made available for studies of the integrated spectra of stellar populations in the context of the Epoch of Reionization.

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