出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：I review here some of the open questions regarding the geometry and emission mechanisms of
galactic black hole candidates. For hard states, I concentrate on the perspective of “disk+Compton
coronae” models (for discussions of jet models, see the papers by Sera Markoff). Specifically,
I discuss the implications from our 10 year long RXTE monitoring campaign of Cyg X-1. I
then present simultaneous RXTE/Chandra observations of the “soft state” black hole candidate
4U 1957+11, and discuss to what extent it does or does not allow one to test “relativistic disk
models”. The use of such models has been claimed to measure black hole spin parameters. I
then briefly present a particularly freaky-weird observation of GX339−4, where the source “fell
off” the usual radio/X-ray correlation in the low/hard state. Questions addressed by the above
observations include: are the Compton corona models unique fits to the data? (No. Jets work
equally well, and simple broken power laws work better still. We argue that the latter models
indicate multiple, broad-band continuum components.) Is there good evidence for a receding
disk as sources transit into the hard state? (The jury is still out.) What does the relativistically
broadened Fe line tell us? (Sometimes the disk, even into quiescence, stays very close to the
central object, in contrast to expectations of ADAF models.) How much better/more necessary
are recently discussed relativistic disk models? (I am very doubtful that such models will ever
usefully measure black hole spin.)
