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Radio detection of the black hole transient H 1743-322 in outburst.

ATel #1349; Corbel, S. (CEA Saclay & Université Paris Diderot) and Tzioumis, A. (ATNF).
on 5 Jan 2008; 21:07 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: S. CORBEL (corbel@discovery.saclay.cea.fr)

Subjects: Radio, Infra-Red, Optical, X-ray, Request for Observations, Black Hole, Transient

Referred to by ATel #: 1352, 1378, 1384, 1385, 1387, 1414

As part of a monitoring campaign of black hole transients, the Australia Telescope Compact Array (ATCA) has observed H1743-322 on 2008, January 3 at the frequencies of 4800 MHz and 8640 MHz. The observations were carried out with the ATCA in the configuration of the 6 km array. We confirm the reactivation of H1743-322 as observed in X-rays by RXTE/ASM (Kalemci et al., ATEL #1348), a radio source being detected at the location of the black hole candidate. H1743-322 is clearly detected around 21 mJy at 4800 MHz and in the range of 10 to 16 mJy at 8640 MHz. The radio spectrum is consistent with optically thin synchrotron emission (spectral index in the range -0.5 to -1.2). This indicates that H1743-322 has likely left the hard state. The detected radio emission is probably the result of a major ejection event during a state transition or H1743-322 may actually be producing minor flares in an X-ray state similar to the steep powerlaw state. Further observations are strongly encouraged.