The High‐Resolution X‐Ray Spectrum of SS 433 Using the Chandra HETGS

Abstract

We present observations of SS 433 using the Chandra High Energy Transmission Grating Spectrometer. Many emission lines of highly ionized elements are detected with relativistic blue and red Doppler shifts. The lines are measurably broadened to 1700 km s~1 (FWHM), and the widths do not depend signiÐcantly on the characteristic emission temperature, suggesting that the emission occurs in a freely expanding region of constant collimation with an opening angle of The blueshifts of lines 1¡ .23 ^ 0¡ .06. from low-temperature gas are the same as those of high-temperature gas within the uncertainties, again indicating that the hottest gas we observe to emit emission lines is already at terminal velocity. This velocity is 0.2699 ^ 0.0007c, which is larger than the velocity inferred from optical emission lines by 2920 ^ 440 km s~1. Fits to the emission-line Ñuxes give a range of temperatures in the jet from 5 ] 106 to 1 ] 108 K. We derive the emission measure as a function of temperature for a four-component model that Ðts the line Ñux data. Using the density-sensitive Si XIII triplet, the characteristic electron density is 1014 cm~3, where the gas temperature is about 1.3 ] 107 K. Based on an adiabatic expansion model of the jet and a distance of 4.85 kpc, the electron densities drop from D2 ] 1015 to 4 ] 1013 cm~3 at distances of (2È20) ] 1010 cm from the apex of the cone that bounds the Ñow. The radius of the base of the visible jet is estimated to be D108 cm, and the mass outÑow rate is 1.5 ] 10~7 yr~1. The kinetic M _ power is 3.2 ] 1038 ergs s~1, which is 1000 times larger than the unabsorbed 2È10 keV X-ray luminosity. The bremsstrahlung emission associated with the lines can account for the entire continuum ; we see no direct evidence for an accretion disk. The image from zeroth order shows extended emission at a scale of D2A, aligned in the general direction of the radio jets.