XMM-Newton observations of SS 433 I. EPIC spectral analysis

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany e-mail: wpb@mpe.mpg.de
² Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152 – 8551, Japan

Received: 2 August 2004
Accepted: 30 September 2004

Abstract

SS433 was observed with XMM-Newton in four consecutive orbits at different binary phases at precessional phases near maximum blue-/red shift between April 2 and April 8, 2003. The light curves in the individual orbits are flat without statistically significant indications for short-term (50 s) intrinsic variability. Orbit-to-orbit flux changes occur predominantly in the hard band; the soft flux (2 keV) stays nearly constant, which implies a jet length in excess of the size of the primary star. The spectral behavior is complex and the high sensitivity and wide bandpass of the XMM-Newton instruments rule out any of the simple continuum models used previously. The data are modeled in terms of thermal emission from conically out-flowing jets and require the existence of an additional emission component, most likely from Compton scattering of the emission from the base of the jet off the cold matter from the surrounding thick disc. The temperature at the base of the jets is about  keV. The density cannot be determined from the current data alone, however, using the most recent mass estimates for the system it must be ~ 10¹² cm^-3 to account for the observed flux during eclipse. The kinetic energy in the jet is then ∼ erg s^-1. In the out-flowing matter Nickel is highly over-abundant (~8 times solar), Fe shows nearly solar abundances, and Si and S are over-abundant by a factor of ~2.