Is SS 433 a misaligned ultraluminous X-ray source? Constraints from its reflected signal in the Galactic plane
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 ˜2 × 1039 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, Θr, 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 disc face-on) decreases with increasing Θr and is ˜3 × 1040 erg s-1 for Θr ≳ Θp = 21°, where Θp 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 Θr and the apparent luminosity.