GCN Circular 2929

RADIO DETECTION OF SGR 1806-20 FOLLOWING A GIANT FLARE

B. M. Gaensler (CfA), C. Kouveliotou (NASA/MSFC, NSSTC), R. Wijers
(University of Amsterdam), M. Garrett (JIVE), M. Finger, P. Woods, S.
Patel (USRA, NSSTC), M. McLaughlin (Jodrell Bank) report on behalf of a
larger team:

We observed the soft gamma-ray repeater SGR 1806-20 with the Very Large
Array, approximately 7 days after the detection of a Giant Flare from
the source (Borkowski, J. et al., 2004, GCN # 2920), on January 3, 2005
for one hour (19:46-20:46 UT). At frequencies of 1.4, 4.9 and 8.5 GHz,
we detect an unresolved radio source at coordinates (J2000) RA
18h08m39.3s, Dec -20o24'39.7", with an approximate uncertainty of 0.1"
in each coordinate. This is consistent with the X-ray position of SGR
1806-20 as given by Kaplan et al., ApJ 564, 935 (2002).  Since this is
the first time the source has been observed in radio, we suggest that we
detected transient emission from a synchrotron wind bubble, as was seen
by Frail et al., Nature, 398, 127 (1999) one to two weeks after a Giant
Flare from SGR 1900+14. The preliminary flux density of the source is
160 +/-10, 78 +/-3 and 45 +/-3, mJy at 1.4, 4.9 and 8.5 GHz,
respectively.  Further observations are planned with the VLA on January
4, 14:15-15:15 UT. We are grateful to the VLA Scheduling Officers (Jim
Ulvestadt and Joan Wrobel) for approving our request for Target of
Opportunity observations of the source.