A superburst from GX 3+1
ATel #68; Erik Kuulkers (SRON & Utrecht University)
on 18 May 2001; 12:57 UT
Credential Certification: Erik Kuulkers (E.KUulkers@sron.nl)
Subjects: Binary, Neutron Star
Referred to by ATel #: 483
A search through the publicly available RXTE/ASM database of GX 3+1
revealed a single flare with an observed peak flux of ~1.1 Crab and
a duration of a few hours. The flare started between 1998 June 8 22:53
and 1998 June 9 00:52 (UT). During the exponential decay, with an e-folding
time of 1.6+/-0.2 hrs (1.5-12 keV), spectral softening is observed. The net
emission (=flare emission minus pre-flare emission) at the peak
is consistent with black-body radiation with a temperature of kT ~2 keV.
The corresponding bolometric net-peak luminosity is ~8x10^37 erg/s at 4.5 kpc.
The pre-flare source luminosity was ~0.2 times the Eddington luminosity.
The characteristics of this flare are very similar to those reported for
other hour-long thermonuclear X-ray events recently found with BeppoSAX/WFC
(e.g. Cornelisse, R., et al. 2000, A&A 357, L21), RXTE/PCA (e.g.
Strohmayer, T.E. 2000, HEAD 32, 24.10) and RXTE/ASM (Wijnands, R. 2001,
ApJ Letters, in press [astro-ph/0103125]) in other low-mass X-ray binaries.
This makes GX 3+1 the sixth source to show such a so-called superburst.
