ULX P13 in NGC 7793: A super-Eddington accreting black hole

Optical observations of P13 in NGC 7793 allowed us to determine for the firsttime the mass of the black hole in an ULX, clearly indicating superEddingtonaccretion. The donor is a B8I star in an eccentric orbit. Swift XRT monitoringrevealed a likely eclipse as well as an extended faint state. Our serendipitousfaint state Chandra spectrum shows evidence of redshifted iron line which wetentatively assign to a jet. We propose to obtain high S/N spectra of thebright, faint and eclipse states. Spectral properties of the bright state willdefine the key signatures of supercritical accretion. Eclipse observation willallow us to constrain the orbit and to possibly reveal evidence of bulk motion.Faint state observations will likely provide the first direct detection of a jet in an ULX. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]