Evidences of the supercritical disc funnel radiation in X-ray spectra of SS 433

TL;DR

This study analyzes X-ray spectra of SS 433, providing evidence of supercritical disc funnel radiation through reflection features and soft excess, advancing understanding of accretion processes in such systems.

Contribution

It introduces a combined thermal jet and reflection model revealing the supercritical disc funnel's role in SS 433's X-ray emission.

Findings

Ionized reflection indicates a supercritical disc funnel.

Soft excess likely originates from the funnel wall.

Reflection is absent in the soft X-ray range.

Abstract

We have analysed the XMM-Newton spectra of SS 433 using a standard model of adiabatically and radiatively cooling X-ray jets. The multi-temperature thermal jet model reproduces well the strongest observed emission line fluxes. The thermal model alone can not reproduce the continuum radiation in the XMM spectral range, the fluorescent iron line and some broad spectral features. Using the thermal jet-plus-reflection model, we find a notable contribution of ionized reflection to the spectrum in the energy range from ~3 to 12 keV. The reflecting surface is highly ionized (xi ~300), the illuminating radiation spectrum is flat and probably strongly absorbed. We conclude that the reflected spectrum is an evidence of the supercritical disc funnel, where the illuminating radiation comes from deeper funnel regions, to be further reflected in the outer visible funnel walls (r >~2*10^11 cm). We have not found any evidences of reflection in the soft 0.8-2 keV energy range, instead, a soft excess is detected, that does not depend on the thermal jet model details. This soft component might prove to be the direct radiation of the visible funnel wall. It is represented here either as black body radiation with the temperature of ~0.1 keV and luminosity of L_bb ~3*10^37 erg/s, or with a multicolour funnel (MCF) model. The soft spectral component has about the same parameters as those found in ULXs.