Detection and Possible Flare of GM Sgr at 29-34 GHz
ATel #45; B. Mason, S. Kulkarni, R. Rutledge, P. Udomprasert, J. Cartwright, T. Pearson, and A. C.S. Readhead (Caltech)
on 20 Sep 1999; 16:19 UT
Credential Certification: R. E. Rutledge (rutledge@srl.caltech.edu)
Subjects: Radio, X-ray, Binary, Transient
GM Sgr (SAX J1819.3-2525 = XTE J1819-254) was observed with the OVRO 40m
telescope, for 10 1-minute integrations, between Sept 16.15566-16.16340
UT, following reports of the bright X-ray outburst (ATEL #43, IAUC # 7253 ). The
observations were made using a dual-beam, Dicke-switching receiver. The
source was detected in four bands averaged over the full 10 minutes, with
flux densities 98 +/- 21, 76 +/- 13, 86 +/- 17, 78 +/- 22 at 27, 29, 31,
and 33 GHz. Between 03:45:08-03:46:07, we see evidence of a sharp peak in
the flux densities in all four bands, with maximum flux densities of 305
+/- 38, 320 +/- 36, 387 +/- 44, and 382 +/- 48 mJy (averaged over the
observation time). While we cannot exclude ground-based, atmospheric, or
instrumental interference as the cause of this peak, the near flat
spectrum is consistent with that expected from a synchtrotron transient
source.
Observations on Sept 17.06826-17.18779 resulted in 95% confidence upper
limits of 29, 15, 11, and 16 mJy at 27, 29, 31, and 33 GHz, respectively.
