Is SS 433 a misaligned ultraluminous X-ray source? Constraints from its reflected signal in the Galactic plane

TL;DR

This study uses reflected X-ray signals in the Galactic plane to constrain SS 433's luminosity, suggesting it could be a misaligned ultraluminous X-ray source, with implications for understanding its emission geometry.

Contribution

The paper provides new constraints on SS 433's luminosity by analyzing reflected X-ray signals, proposing it may be a misaligned ULX, which was not previously established.

Findings

Upper limit of ~2×10^39 erg/s on SS 433's intrinsic luminosity in 2-10 keV band.

Upper limit of ~3×10^40 erg/s on apparent luminosity for certain emission cone angles.

Reflection analysis leaves open the possibility of SS 433 being a misaligned ULX.

Abstract

We evaluate the emission that must arise due to reflection of the putative collimated X-ray radiation of SS 433 by atomic gas and molecular clouds in the Galactic plane and compare the predicted signal with existing RXTE and ASCA data for the region of interest. Assuming that the intrinsic X-ray spectrum of SS 433 is similar to that of ultraluminous X-ray sources (ULXs), we obtain an upper limit of $\sim 2\times 10^{39}$ erg s$^{-1}$ on its total (angular-integrated) luminosity in the 2--10 keV energy band, which is only weakly dependent on the half-opening angle, $\Theta_r$, of the emission cone. In contrast, the upper limit on the apparent luminosity of SS 433 (that would be perceived by an observer looking at its supercritical accretion disk face-on) decreases with increasing $\Theta_r$ and is $\sim 3\times 10^{40}$ erg s$^{-1}$ for $\Theta_r\gtrsim\Theta_p=21\deg$, where $\Theta_p$ is the precession angle of the baryonic jets (assuming that the emission cones precess in the same manner as the jets). This leaves open the possibility that SS 433 is a misaligned ULX. Further investigation of the reflection signal from the molecular clouds using higher angular resolution observations could improve these constraints with the potential to break the degeneracy between $ \Theta_r $ and the apparent luminosity.