Journal Article

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

A. Medvedev and S. Fabrika

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 1, pages 479-491
Published in print February 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI:
Evidence of supercritical disc funnel radiation in X-ray spectra of SS 433

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We analysed the XMM–Newton spectra of SS 433 using a standard model of adiabatically and radiatively cooling X-ray jets. The multitemperature thermal jet model reproduces the strongest observed emission line fluxes well. Fitting the He- and H-like iron line fluxes, we find that the visible blue jet base temperature is ∼17 keV, the jet kinetic luminosity Lk∼ 2 × 1039 erg s−1 and the absorbing column density NH∼ 1.5 × 1022 cm−2. All these parameters are in line with previous studies. The thermal model alone cannot reproduce the continuum radiation in the XMM spectral range, nor the fluorescent iron line and some of the 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 (ξ∼ 300), and the illuminating radiation photon index changes from Γ≈ 2 (a flat spectrum) in the range 7–12 keV to Γ≈ 1.6 in the range 4–7 keV, and to Γ≲ 1 in the range 2–4 keV. We conclude that the reflected spectrum is evidence of the supercritical disc funnel, whereby the illuminating radiation comes from deeper funnel regions, to be further reflected in the outer visible funnel walls (r≳ 2 × 1011 cm). In the multiple scatterings in the funnel, the harder radiation >7 keV may survive absorption, but softer radiation is absorbed, making the illuminating spectrum curved. We have not found any evidence of reflection in the soft 0.8–2 keV energy range; instead, a soft excess is detected, which does not depend on the details of the thermal jet model. However, the soft component spectrum is basically unknown. This soft component might prove to be the direct radiation of the visible funnel wall. It is represented here either as blackbody radiation with a temperature of θbb≈ 0.1 keV and a luminosity of Lbb∼ 3 × 1037 erg s−1, or with a multicolour funnel model. The soft spectral component has parameters roughly the same as those found in ultraluminous X-ray sources.

Keywords: binaries: close; stars: individual: SS 433; X-rays: binaries

Journal Article.  12110 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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