* Astronomy

Blobrana · L

RE: H1743-322

Blobrana · L

VLBA, RXTE Team Up to Pinpoint Black Hole's Outburst

Astronomers have gained an important clue about a ubiquitous cosmic process by pinpointing the exact moment when gigantic "bullets" of fast-moving material were launched from the region surrounding a black hole. They made this breakthrough by using the ultra-sharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), along with NASA's Rossi X-ray Timing Explorer (RXTE) satellite, to study an outburst from a system including a black hole and its companion star in 2009.
Black holes in such binary-star systems can pull material from their companions. That material forms a rapidly-rotating disk of material around the black hole, and "jets" of material are thrown outward perpendicular to the disk. Most of the time, the jets show a steady flow of material, but occasionally the steady jets disappear and superfast "bullets" of material are ejected at speeds approaching that of light. Such an outburst can produce as much energy in an hour as the Sun emits in five years.
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Blobrana · L

Title: Disc-jet coupling in the 2009 outburst of the black hole candidate H1743-322
Authors: J. C. A. Miller-Jones (1), G. R. Sivakoff (2), D. Altamirano (3), M. Coriat (4), S. Corbel (5), V. Dhawan (6), H. A. Krimm (7), R. A. Remillard (8), M. P. Rupen (6), D. M. Russell (9), R. P. Fender (4), S. Heinz (10), E. G. Körding (11), D. Maitra (12), S. Markoff (3), S. Migliari (13), C. L. Sarazin (14), V. Tudose (15) ((1) ICRAR - Curtin, (2) U. Alberta, (3) U. Amsterdam, (4) U. Southampton, (5) U. Paris Diderot, (6) NRAO, (7) NASA/GSFC, (8) MIT, (9) IAC, (10) U. Wisconsin-Madison, (11) U. Nijmegen, (12) U. Michigan, (13) U. Barcelona, (14) U. Virginia, (15) ASTRON)

We present an intensive radio and X-ray monitoring campaign on the 2009 outburst of the Galactic black hole candidate X-ray binary H1743-322. With the high angular resolution of the Very Long Baseline Array, we resolve the jet ejection event and measure the proper motions of the jet ejecta relative to the position of the compact core jets detected at the beginning of the outburst. This allows us to accurately couple the moment when the jet ejection event occurred with X-ray spectral and timing signatures. We find that X-ray timing signatures are the best diagnostic of the jet ejection event in this outburst, which occurred as the X-ray variability began to decrease and the Type C quasi-periodic oscillations disappeared from the X-ray power density spectrum. However, this sequence of events does not appear to be replicated in all black hole X-ray binary outbursts, even within an individual source. In our observations of H1743-322, the ejection was contemporaneous with a quenching of the radio emission, prior to the start of the major radio flare. This contradicts previous assumptions that the onset of the radio flare marks the moment of ejection. The jet speed appears to vary between outbursts, with a possible positive correlation with outburst luminosity. The compact core radio jet reactivated on transition to the hard intermediate state at the end of the outburst, and not when the source reached the low hard spectral state. Comparison with the known near-infrared behaviour of the compact jets suggests a gradual evolution of the compact jet power over a few days near the beginning and end of an outburst.

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Blobrana · L

Title: A failed outburst of H1743-322
Authors: Fiamma Capitanio (1) ; Tomaso Belloni (2), Melania Del Santo (1) ; Pietro Ubertini (1) ((1) IASF-Roma INAF, Rome Italy, (2) Osservatorio Astronomico di Brera-INAF Italy)

We report on a campaign of X-ray and soft gamma-ray observations of the black hole candidate H 1743-322 (also named IGR J17464-3213), performed with the RXTE, INTEGRAL and Swift satellites. The source was observed during a short outburst between 2008 October 03 and 2008 November 16. The evolution of the hardness-intensity diagram throughout the outburst is peculiar, in that it does not follow the canonical pattern through all the spectral states (the so called q-track pattern) seen during the outburst of black-hole transients.
On the contrary, the source only makes a transition from the Hard State to the Hard-Intermediate State. After this transition, the source decreases in luminosity and its spectrum hardens again. This behaviour is confirmed both by spectral and timing analysis. This kind of outburst has been rarely observed before in a transient black hole candidate.

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