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Complex evolution of radio spectrum in GRO J1655-40

ATel #437; M. P. Rupen (NRAO/GSFC), V. Dhawan, A. J. Mioduszewski (NRAO)
on 7 Mar 2005; 19:33 UT
Credential Certification: Michael P. Rupen (mrupen@nrao.edu)

Subjects: Radio, Binary, Black Hole, Transient

Referred to by ATel #: 487

The radio spectrum of the black hole X-ray binary GRO J1655-40 has undergone rapid changes over the past few days, according to observations by the Very Large Array (VLA). On Mar. 4th, data taken between 12:09 and 12:41 UT give flux densities of 1.2 +/- 0.2, 1.9 +/- 0.1, and 1.5 +/- 0.1 mJy at 1.425, 4.860, and 8.460 GHz, respectively; on Mar. 6th, observations between 12:16 and 12:56 UT yield values of 1.8 +/- 0.2, 1.3 +/- 0.1, and 1.2 +/- 0.1 mJy at the same frequencies. Combined with previous observations (ATEL #419, ATEL #425, ATEL #434) these data suggest a small radio flare sometime between Feb. 27th and Mar. 4th (i.e., during or just after the X-ray plateau, ATEL #432, ATEL #433), followed by a return to the earlier fairly flat spectrum. The radio light curve is posted at:

http://www.aoc.nrao.edu/~mrupen/XRT/GRJ1655-40/grj1655-40.shtml

Further radio observations are planned.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Radio light curve of GRO J1655-40