Photometric Mass Estimate for the Compact Component of SS 433: And Yet It Is a Neutron Star

Understand

After 33 years of extensive studies of SS 433, we have learnt much about this unique system with moving emission lines in the spectrum.

• The orbital inclination is known from spectroscopic observations of moving lines; the distance is derived from radio interferometry of relativistic jets; the mass ratio of its components is determined from X-ray observations of jets' eclipses.
• In 2005, the accretion donor was detected as an A4 - A8 giant, and its contribution to eclipse light was measured spectroscopically.
• In the present paper, the A-type star was detected via multicolor photometry on the basis of its Balmer jump.