High Resolution Chandra HETG spectroscopy of V404 Cygni in Outburst

Understand

As one of the best-characterized stellar-mass black holes, with good measurements of its mass, distance and inclination, V404 Cyg is the ideal candidate to study Eddington-limited accretion episodes.

• After a long quiescent period, V404 Cyg underwent a new outburst in June 2015.
• We obtained two Chandra HETG exposures of 20 ksec and 25 ksec.
• Many strong emission lines are observed; the ratio of Si He-like triplet lines gives an estimate for the formation region distance of $4\times10^{11}$ cm, while the higher ionization Fe XXV He-like triplet gives an estimate of $7\times10^9$ cm.