Massive Black-hole X-ray binaries: Accretion-wind interaction and evolutionary context

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When both stars in a binary system are very massive (10 solar masses), highly exotic systems comprised of black holes (BH), neutron stars (NS), and Wolf-Rayet stars (WR) can result. This project seeks a global revision of the masses in BH+WR systems, leading ultimately to more precise BH mass estimates and a better understanding of BH formation, the complex interaction between the BH's radiation field and the WR wind, and the evolution of BH+WR binaries in general. A similar analysis of a recently discovered population of BH+WR binary candidates in the dwarf galaxy IC 10 will also be undertaken. This work will support a graduate student and the team's various outreach and educational activities. The proposed research will combine in-hand photometry and spectroscopy of the BH-WR binaries IC 10 X-1 and NGC 300 X-1 to carry out an orbital phase resolved analysis of emission lines to model the ionization structure of the WR wind and determine BH masses with improved accuracy. In a similar manner, observations and analysis of newly discovered X-ray binary candidates in IC 10 that also show indications of mass loss plus many of the same features of IC 10 X-1 will be carried out for comparison. The possible connection between enhanced BH masses with low metallicity environments and the formation channel(s) for the most massive stellar BHs are both of great interest due to their implications for Gamma-ray burst progenitors, gravitational wave sources, and the seeds of supermassive BHs. The research team is currently conducting multi-wavelength observations of these systems (e.g., Chandra, XMM, NuStar, HST, Gemini, NOAO) to confront model predictions. The goal of these studies is to explain the time resolved structure of the X-ray eclipse light-curve, its energy dependence, and make predictions for the infrared and optical light-curves and line profiles that will be tested in upcoming and planned missions such as JWST, Athena, XIPE, and STROBE-X.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.