A Faint, Steep Spectrum Burst from the Radio Transient GCRT J1745-3009

Scott D. Hyman Subhashis Roy Sabyasachi Pal T. Joseph W. Lazio Paul S. Ray Namir E. Kassim S. Bhatnagar


(1) Department of Physics and Engineering, Sweet Briar College, Sweet Briar, VA 24595
(2) ASTRON, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands.
(3) National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune, India
(4) Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375-5351
(5) E. O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, DC 20375-5352
(6) Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375-5351
(7) National Radio Astronomy Observatory, Array Operations Center, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387

Paper: ApJLetters, submitted

EPrint Server: astro-ph/0701098


Abstract:

GCRT J1745-3009 is a transient bursting radio source located in the direction of the Galactic center. It was discovered in a 330 MHz VLA observation from 2002 September 30-October 1 and subsequently rediscovered in a 330 MHz GMRT observation from 2003 September 28 by Hyman et al. Here we report a new radio detection of the source in 330 MHz GMRT data taken on 2004 March 20. The observed properties of the single burst detected differ significantly from those measured previously, suggesting that GCRT J1745-3009 was detected in a new physical state. The 2004 flux density was 0.05 Jy, 10* weaker than the single 2003 burst and 30* weaker than the five bursts detected in 2002. We derive a very steep spectral index, alpha = -13.5 +/- 3.0, across the bandpass, a new result previously not detectable due to limitations in the analysis of the 2002 and 2003 observations. Also, the burst was detected for only 2 min., in contrast to the 10 min. duration observed in the earlier bursts. Due to sparse sampling, only the single burst was detected in 2004, as in the 2003 epoch, and we cannot rule out additional undetected bursts that may have occurred with the same 77 min. periodicity observed in 2002 or with a different periodicity. Considering our total time on source throughout both our archival and active monitoring campaigns, we estimate the source exhibits detectable bursting activity 7% of the time.


Preprints available from the authors at shyman@sbc.edu , or the raw TeX (no figures) if you click here.

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