SS 433: Two robust determinations fix the mass ratio

• Published in: Astronomy and astrophysics (Berlin) Vol. 619; p. L4
• Main Author: Bowler, M. G.
• Format: Journal Article
• Language: English
• Published: Heidelberg EDP Sciences 01.11.2018
• Subjects: binaries: close; circumstellar matter; stars: individual: SS 433
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201834121

Context. The unique Galactic microquasar SS 433 is an X-ray binary with a 13.08 day orbital period. Over some forty years, estimates of the mass of the compact object have spanned the range 1–30 solar masses; from neutron star to massive stellar black hole. Aims. To fix the mass ratio q and hence the mass of the super-Eddington accretor. Methods. We present a new and robust estimate of q derived from data on the circumbinary disk and compare it with a recent determination from the observed constancy of the binary period. Results. These two robust analyses agree to a remarkable extent. They reinforce each other; q is ∼0.7 and the mass of the compact object 15 ± 2 M⊙. Conclusions. The mass is such as to identify the compact object as a massive stellar black hole.