Program: GN-2016A-FT-30

Title:A Candidate Red Supergiant High-Mass X-ray Binary in M31
PI:Emily Levesque
Co-I(s): Trevor Dorn-Wallenstein

Abstract

We have recently identified a candidate for what may be the first detection of a high-mass X-ray binary (HMXB) with a red supergiant (RSG) donor star. While much work has gone into the study of HMXBs with main sequence companions, HMXBs with evolved companions are relatively rare and thus poorly understood, and no HMXB with an RSG donor star has ever been detected. These RSG HMXB systems are particularly compelling: they represent an important evolutionary phase for massive binary systems, the large diffuse envelopes of RSGs offer the possibility of studying exotic accretion rates not usually found in HMXBs, and they are excellent candidates for studying both common envelope systems with a compact primary and possible proto-Thorne-Zytkow objects (cool massive stars with an embedded neutron star core). Using data from the Chandra archive and the Local Group Galaxy Survey, we have recently identified a presumed M31 RSG with an associated hard X-ray source. Here we propose to obtain optical spectrophotometry to confirm this object's membership in M31, compare its optical SED with stellar models to determine the presumed donor star's physical properties, and search for evidence of a compact companion through possible detection of emission lines from an accretion disk or hot spot.

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