Gradual Brightening of SGR 1806-20
ATel #313; Peter M. Woods (USRA/NSSTC), Chryssa Kouveliotou (MSFC/NSSTC), Ersin Gogus (Sabanci Univ), Sandy Patel (USRA/NSSTC), Kevin Hurley (UCB), and Jean Swank (NASA/GSFC)
on 28 Jul 2004; 17:45 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Peter Woods (Peter.Woods@nsstc.nasa.gov)
Subjects: Infra-Red, X-ray, Gamma Ray, Request for Observations, Soft Gamma-ray Repeater
Referred to by ATel #: 324
The Soft Gamma Repeater SGR 1806-20 became particularly burst active in May
2004 (GCN 2603, 2604) and has remained active up through the present. Over
this interval, both the pulsed X-ray flux as measured with the RXTE/PCA and the
phase-averaged X-ray flux as measured with Chandra/ACIS have been 2 to 3 times
higher than ever observed since the discovery of the X-ray counterpart in
1993. In the Chandra X-ray data, we detect a thermal component in the X-ray
spectrum of SGR 1806-20 for the first time. We measure a blackbody temperature
of 0.54 +/- 0.07 and a photon index of -1.44 +/- 0.15. Surprisingly, the
pulsed flux as measured during several RXTE pointings over the last two months
has actually risen by 40-50% as the burst rate declined during the same time
interval. Given the unprecedented, continued brightening of the source,
additional observations, particularly in soft and hard X-rays and IR, are
encouraged.
