An unusual thermonuclear flash from a common burster
GX 3+1 is a bright and well-known low-mass X-ray binary. Normally,
a few times per day it shows short (less than 10 sec duration) and
strong thermonuclear, or type I, X-ray bursts. INTEGRAL detected on
August 31, 2004 an unusual type I X-ray burst. Its duration was about
30 minutes. The peculiar burst is characterised by 2 distinct phases:
an intial short spike of ~6 sec, similar to the normal type I X-ray
bursts, followed by a remarkable extended decay of cooling emission.
The discovery is reported by Chenevez et al. (
2006,astro-ph/0512559).
Although it seems most probable that the burst is due to unstable
burning of a mixed hydrogen/helium layer involving an unusually
large amount of hydrogen, other scenario's (involving unstable burning
of either pure helium or carbon) cannot be ruled out.
Data displayed in the figure are from JEM-X in the 3-20 keV range and
plotted with 5 s bins. The main peak (t = 0 s) occurred at UTC 18:55:11
on 31 August 2004.
