PI: Todd Hillwig, Valparaiso University, firstname.lastname@example.org
Address: Physics Department, 1610 Campus Drive, Valparaiso, IN 46383, USA
CoI: Douglas R. Gies, Georgia State University
Title: Confirmation of the Mass Donor Star in the Unique Microquasar SS 433
Abstract: We have detected an absorption line component in the blue spectrum of SS 433 that probably is associated with the long-sought mass donor star in this unusual X-ray binary. The results suggest that the donor is an A-supergiant and the companion is a low mass black hole. However, recent spectroscopic signatures of a potential circumbinary disk suggest a much more massive black hole companion. The mass, radius, effective temperature, and gravity of the mass donor star are the key parameters needed to resolve this controversy. Here we propose to obtain low resolution spectra in the near-UV and blue in order to detect and characterize the Balmer jump feature in the mass donor star's spectrum. The observations will need to be obtained at an orbital and precessional phase optimized for detection of the supergiant. The spectra will allow us to determine the basic properties of the mass donor and to establish the current evolutionary stage of this enigmatic microquasar.
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