# Mass ratio in SS433 revisited

## TL;DR

This study revisits the mass ratio of the SS433 binary system using recent VLTI measurements, confirming a high mass ratio and suggesting the compact object is a stellar-mass black hole.

## Contribution

It provides a revised estimate of the mass ratio in SS433 based on new observational data, supporting the black hole hypothesis for the compact object.

## Key findings

- Mass ratio in SS433 is at least 0.6.
- Compact object mass is estimated to be 5-9 solar masses.
- The results support the black hole nature of the compact object.

## Abstract

We revisit the determination of binary mass ratio in the Galactic microquasar SS433 based on recent GRAVITY VLTI measurements of mass and angular momentum outflow through a circumbinary disc. The new observations combined with the constancy of the binary orbital period over $\sim 30$ yrs confirm that the mass ratio in SS433 is $q=M_\mathrm{x}/M_\mathrm{v}\gtrsim 0.6$. For the assumed optical star mass $M_\mathrm{v}$ ranging from $\sim 8$ to 15 $M_\odot$ such a mass ratio suggests a low limit of the compact object mass of $M_\mathrm{x}\sim 5-9 M_\odot$, placing the compact object in SS433 as a stellar-mass black hole.