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Outburst of GX 339-4

ATel #85; D. M. Smith (Space Sciences Laboratory, U. C. Berkeley), J. H. Swank (NASA/Goddard), W. A. Heindl (Center for Astrophysics and Space Science, U. C. San Diego), and R. A. Remillard (MIT)
on 3 Apr 2002; 19:42 UT
Distributed as an Instant Email Notice Transients
Credential Certification: David M. Smith (dsmith@ssl.berkeley.edu)

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

Referred to by ATel #: 95, 120, 196, 231

Observations with the Rossi X-ray Timing Explorer (RXTE) show that the suspected black-hole binary GX 339-4 has become active after three years in quiescence. At 15:30 UT on 3/26/02, the Proportional Counter Array (PCA) measured an unabsorbed flux of 9.4 x 10^-11 ergs/cm2/s from 2-10 keV, about an order of magnitude higher than the upper limits which had been detected in a year of previous weekly monitoring. At this time the spectrum was well fit by a power-law of index 1.9 +/- 0.5 and an absorption column nH of 2.8 +/- 0.6 x 10^22 /cm2.

At 14:30 UT on 4/2/02, the source was more than an order of magnitude brighter, 1.4 x 10^-9 ergs/cm2/s at 2-10 keV, with a power-law index of 1.56 +/- 0.01 and absorption column of 0.89 +/- 0.18 x 10^22 /cm2. The All-Sky Monitor (ASM) on RXTE reported the source as active at 13:10 UT on 4/3/02, with an average rate of 4.7 cts/s. Further RXTE observations are in progress.

Multiwavelength observations are requested, particularly monitoring of radio emission associated with jet ejections, but also IR/optical observations of the rapidly evolving accretion disk.