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Dynamical Evidence for a Black Hole in GX 339-4
We present outburst spectroscopy of GX 339-4 that may reveal the motion of its elusive companion star. N III lines exhibit sharp emission components moving over ~300 km s-1 in a single night. The
A Long, Hard Look at the Low/Hard State in Accreting Black Holes
We present the first results of coordinated multiwavelength observations of the Galactic black hole GX 339-4 in a canonical low/hard state, obtained during its 2004 outburst. XMM-Newton observed the
A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
Using the Very Long Baseline Array, we have measured a trigonometric parallax for the micro quasar GRS 1915+105, which contains a black hole and a K-giant companion. This yields a direct distance
The Distance and Interstellar Sight Line to GX 339–4
The distance to the black hole binary GX 339-4 remains a topic of debate. We examine high-resolution optical spectra of the Na D lines resolving the velocity structure along the line of sight. We
The magnetic nature of disk accretion onto black holes
It is reported that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655 - 40 must be powered by a magnetic process that can also drive accretion through the disk, demonstrating that disk accretion onto black holes is a fundamentally magnetic process.
Mass transfer between double white dwarfs
Three periodically variable stars have recently been discovered (V407 Vul, P=9.5 min; ES Cet, P=10.3 min; RX J0806.3+1527, P=5.3 min) with properties that suggest that their photometric periods are
A radio-pulsing white dwarf binary star
The discovery is reported of a white dwarf/cool star binary that emits from X-ray to radio wavelengths and the spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which suggests that AR Sco is primarily spin-powered.
The Mass Donor of Scorpius X-1 Revealed
We present the first detection of the mass donor star in the prototype X-ray binary Scorpius X-1. Phase-resolved spectroscopy revealed narrow emission line components from the irradiated secondary
Simultaneous Chandra and RXTE Spectroscopy of the Microquasar H1743–322: Clues to Disk Wind and Jet Formation from a Variable Ionized Outflow
We observed the bright phase of the 2003 outburst of the Galactic black hole candidate H1743-322 in X-rays simultaneously with Chandra and RXTE on four occasions. The Chandra HETGS spectra reveal
Swift Observations of the Cooling Accretion Disk of XTE J1817-330
The black hole candidate X-ray transient XTE J1817-330 was observed by the Swift satellite over 160 days of its 2006 outburst with the XRT and UVOT instruments. At the start of the observations, the