Detecting Stripped Stars While Searching for Quiescent Black Holes

J. Bodensteiner, M. Heida, M. Abdul-Masih, D. Baade, G. Banyard, D. M. Bowman, M. Fabry, A. Frost, L. Mahy, P. Marchant, A. Mérand, M. Reggiani, Th. Rivinius, H. Sana, F. Selman, T. Shenar

Submitted on 1 July 2022


While the number of stellar-mass black holes detected in X-rays or as gravitational wave sources is steadily increasing, the known population remains orders of magnitude smaller than predicted by stellar evolution theory. A significant fraction of stellar-mass black holes is expected to hide in X-ray-quiet binaries where they are paired with a "normal" star. Although a handful of such quiescent black hole candidates have been proposed, the majority have been challenged by follow-up investigations. A confusion that emerged recently concerns binary systems that appear to contain a normal B-type star with an unseen companion, believed to be a black hole. On closer inspection, some of these seemingly normal B-type stars instead turn out to be stars stripped of most of their mass through an interaction with their binary companion, which in at least two cases is a rapidly rotating star rather than a compact object. These contaminants in the search for quiescent black holes are themselves extremely interesting objects as they represent a rare phase of binary evolution, and should be given special attention when searching for binaries hosting black holes in large spectroscopic studies.


Comment: 7 pages, 5 figures

Subjects: Astrophysics - Solar and Stellar Astrophysics; Astrophysics - High Energy Astrophysical Phenomena