HETG Spectroscopy of WR 48a: a superluminous dusty Wolf-Rayet star

Chandra and XMM images of the G305 galactic star-forming region reveal a surprisingly bright X-ray source associated with the dusty WC8 binary WR 48a. The XMM-Newton PN spectrum of WR 48a is heavily absorbed with temperature components at 1 and 3 keV, the hotter component dominating the observed flux. WR 48a appears to be the most X-ray luminous Wolf-Rayet star known, after the WR+NS/BH binary Cyg X-3. Its Lx, comparable to the LBV binary eta Carinae, is >10 times higher than other WR+O binaries like WR 140. We propose to obtain HEG/MEG spectra of WR 48a to measure the width of the emission lines, determine abundances, and measure key H- and He-like diagnostics to assess the location and ionization timescale of the X-ray shocks.