Recent and past activity of the supergiant fast X-ray transient IGR J17544-2619 as seen by INTEGRAL
ATel #1266; E. Kuulkers (ESA/ESAC, Spain), D. Risquez Oneca (LAEFF/INTA, Spain), S. Brandt (DNSC, Denmark), S. Shaw (Southampton, UK/ ISDC, Switzerland),V. Beckmann (ISDC, Switzerland), J. Chenevez (DNSC, Denmark), T. J.-L. Courvoisier (ISDC, Switzerland), A. Domingo (LAEFF/INTA, Spain), K. Ebisawa (ISAS, Japan), P. Jonker (SRON, The Netherlands), P. Kretschmar (ESA/ESAC, Spain), C. Markwardt (GSFC, USA), T. Oosterbroek (ESA/ESTEC, The Netherlands), A. Paizis (INAF-IASF, Italy), C. Sanchez-Fernandez (ESA/ESAC, Spain), R. Wijnands (UvA, The Netherlands)
on 9 Nov 2007; 16:04 UT
Credential Certification: Erik Kuulkers (email@example.com)
Subjects: Optical, X-ray, Gamma Ray, Binary, Neutron Star, Transient, Variables
Following the report of the recent activity seen by Swift/BAT (ATel #1265) we
note that the supergiant fast X-ray transient IGR J17544-2619 was also active
about one and a half month earlier. During our INTEGRAL Galactic Bulge
monitoring observations (see ATels #438, #874 and #1005) on UT 2007 Sep 21
04:10-07:52 the source flared on timescales of half an hour, from around the
IBIS/ISGRI detection limits of one pointing (about 10 mCrab) up to
36 +/- 5 mCrab (20-60 keV). The average IBIS/ISGRI detection significance over the
12.6 ksec observation is about 14 sigma (20-60 keV).
No simultaneous activity was seen from the optical counterpart with the OMC
(V-band magnitude stayed near 12.8); the source was not detected by JEM-X
with an upper limit of about 20 mCrab (3-20 keV).
Activity prior to this was also seen by Kuulkers et al. (2007, A&A 466, 595)
with INTEGRAL on UT 2005, October 15, when IGR J17544-2619 reached a flux of up to about
60 mCrab (IBIS/ISGRI; 20-60 keV). We note that the recent hard X-ray activity of the source,
together with that reported in the literature (ATel #190; #192; #252; Walter et al. 2006,
A&A 453, 133; Kuulkers et al. 2007), can not be described with a recurrence period of
about 165 days suggested by Walter et al. (2006).
The INTEGRAL Galactic Bulge monitoring results (JEM-X and IBIS/ISGRI light
curves and mosaic images) are publicly available at