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ATEL # 2141; Erik Kuulkers (ISOC, ESA/ESAC, Spain)
on 31 Jul 2009; 14:34 UT
Password Certification: Erik Kuulkers (email@example.com)
Subjects: X-ray, Binaries, Neutron Stars, Variables
As a side result of the search for superbursts in the RXTE/ASM archive up to June 2009 of all type I X-ray bursters known to date (ATel #2140), four high, subsequent, ASM dwells in a time span of about 6 min were found near UT 1999 August 17 04:20 of the source SAX J1712.6-3739. During that time the 1.5-12 keV source flux decayed from 0.67+/-0.3 to 0.61+/-0.3 Crab. 7.9 hours earlier and 5.2 hours later the source was persistent at a low flux level of about 0.01 Crab. The 1.5-12 keV count rate e-folding decay time of the event is 40[+50,-14] minutes. Analysis of the 3-channel ASM data (see Kuulkers 2002, A&A 383, L5; Keek et al. 2008, A&A 479, 177) shows that the flare emission is consistent with a black-body spectrum of temperatures between 1.9+/-0.1 keV and 2.5+/-0.2 keV.
I suggest this event to be an intermediate-duration burst (see Cumming et al. 2006, ApJ 646, 429, for a definition). This would be the first seen from SAX J1712.6-3739, strengthening the source being an ultra-compact X-ray binary (see in 't Zand et al. 2007, A&A 465, 953).