Discovery of orbital Eccentricity and Evidence for orbital Period Increase of SS433

Abstract

The examination of long-term (1979-2020) photometric observations of SS433 enabled us to discover a non-zero orbital eccentricity of $e=0.05\pm \mathrm{0.01.}$ We have also found evidence for a secular increase in the orbital period at a rate of ${\dot{P}}_{\mathrm{b}}=(1.0\pm 0.3)\times 10^{-7}$ s s${}^{-1}$. The binary orbital period increase rate makes it possible to improve the estimate of the binary mass ratio $q=M_{\mathrm{X}}/M_{\mathrm{V}}>0.8$, where $M_{\mathrm{X}}$ and $M_{\mathrm{V}}$ are the masses of the relativistic object and the optical star, respectively. For an optical star mass of 10${\mathrm{M}}_{\odot }$, the mass of the relativistic object (a black hole) is $M_{\mathrm{X}}>8{\mathrm{M}}_{\odot }$. A neutron star in SS433 is reliably excluded because in that case the orbital period should decrease, in contradiction to observations. The derived value of ${\dot{P}}_{\mathrm{b}}$ sets a lower limit on the mass-loss rate in the Jeans mode from the binary system $\gtrsim 7\times 10^{-6}{\mathrm{M}}_{\odot }{\mathrm{yr}}^{-1}$. The discovered orbital ellipticity of SS433 is consistent with the model of the slaved accretion disc tracing the precession of the misaligned optical star's rotational axis.

5 pages, 4 figures + Appendix. Accepted for publication in MNRAS Letters

References in corpus (5)

• Spectroscopic Observations of the Mass Donor Star in SS 433
• Distances to Galactic X-ray Binaries with Gaia DR2
• Fluctuations and symmetry in the speed and direction of the jets of SS433 on different timescales
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• Simulations of the progenitors of black hole-neutron star gravitational wave sources
• An Overview of Compact Star Populations and Some of Its Open Problems
• Spectral and photometric variability of SS 433 observed with XRISM and simultaneous optical and near-infrared telescopes
• Simulation-calibrated Bayesian inference for progenitor properties of the microquasar SS 433