Soft Gamma Repeater SGR 0501+4516: GBM Detection of multiple bursts
C. Kouveliotou (NASA/MSFC), P.N. Bhat (UAH), E. Bissaldi (MPE), M.S.
Briggs (UAH), V. Connaughton (UAH), R. Diehl (MPE), G.J. Fishman
(NASA/MSFC), L. Gibby (NASA/MSFC), J. Greiner (MPE), A.S. Hoover (LANL),
A.J. van der Horst (NASA/ORAU), R.M. Kippen (LANL), G.G. Lichti (MPE),
C.A. Meegan (NASA/MSFC), S. McBreen (MPE), W.S. Paciesas (UAH), R.D.
Preece (UAH), H. Steinle (MPE), A. von Kienlin (MPE), M.S. Wallace
(LANL), and C.A. Wilson-Hodge (NASA/MSFC)report:
The GLAST Burst Monitor has thus far triggered on 23 bursts from SGR
0501+5416, newly discovered with Swift (Holland et al. 2008, GCN Circ.
8112, Barthelmy et al. 2008, GCN 8113 and GCN 8119). Additional
un-triggered bursts have been detected in the data; a complete census is
underway. The first GBM trigger was on 2008, August 22 (von Kienlin et
al. 2008, GCN 8122). The GBM team will issue future individual GCN
Circulars only for exceptionally bright SGR events.
The GBM triggered-event rate has peaked at 14 events on 2008 August 23
and seems to be slowing down with only 2 on 2008, August 26. We have so
far identified five events in common with Swift and three with
Konus-Wind. The event intensities range from weak to very bright; their
durations range between ~50 - 500 msec. Event spectra are on the average
best fit with a power law with an exponential cutoff and peak energies ~
40-50 keV. Taking into account the source location at the Galactic
anti-center, we assume a distance between 2-5 kpc, which corresponds to
a range of burst luminosities ~10^37 - 10^40 ergs.