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From: starrfie@hydro.la.asu.edu (Sumner Starrfield) Subject: Soft Gamma Repeater! Date: Sat, 16 Oct 93 9:18:06 MST According to a report in IAU circular 5880, a source of soft gamma-ray flashes has been identified. Soft Gamma Repeaters are objects which briefly produce short soft gamma-ray flashes (blackbody, with temperatures of ~10 keV, less than 1 second long) more than once. In this they differ from classical Gamma Ray Bursters, which produce (as far as we know) single episodes (milliseconds to minutes long) of hard gamma-ray emission (power peaks at a few hundred keV, observed at energies up to 10 GeV). There are three SGRs known. The subject of this message, SGR 1806-20, has been observed over more than 100 flashes, mostly in the early 1980's. Recently, Kulkarni & Frail (Nature, a couple of months ago, before 1806-20 started up again) found a radio source, which turned out to be rare filled-plerion supernova remnant, in the 1806-20 error box. After a long quiescent period, SGR 1806-20 started flashing again a few weeks ago. A call for monitoring at all wavelengths was issued by IAU circular, and I repeated this call to the net, suyggesting that it would be a good target for amateurs to photograph. The ASCA X-ray telescope was observing the supernova remnant when the SGR flashed on Oct 9.934 UT. They found a simultaneous burst of X-ray counts from a persistent X-ray source which is coincident with the supernova remnant. Unless Nature is viscious this means that SGRs come from supernova remnants! Were any of you observing this location (18h05m42s,-20o25'10" eq. 1950) optically at this time (UT Oct 9 2225, nighttime in Europe, Africa and western Asia)? If so, I would be interested in hearing your results, either positive or negative, in observing a flash of light from this object.
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