INTEGRAL observes A1744-361 (XTE J1748-361) in hard X-rays

ATel #266; S. A.Grebenev (IKI, Moscow), P. Goldoni (CEA, Saclay), V. Schönfelder (MPE, Garching), J.-P. Roques (CESR, Toulouse), R. A.Sunyaev (IKI, Moscow & MPA, Garching), T. Courvoisier (ISDC, Versoix), C. Winkler (ESA/ESTEC, Noordwijk)
on 9 Apr 2004; 17:09 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: S.A.Grebenev (sergei@hea.iki.rssi.ru)

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The X-ray transient A1744-361 (XTE J1748-361) was detected with ISGRI/IBIS on April 7-8, 2004 during the INTEGRAL Galactic Center Deep Exposure observation. The average flux in the 17-45 keV band was equal to 19.8+/-1.6 mCrab (the S/N ratio was 13). The photon spectrum was extending to at least 100 keV. The source was seen neither in March during previous GCDE observations nor in the beginning of April during the Galactic Center Open Program observation (the 3-sigma upper limit was 1.5 mCrab). The simultaneous reactivation of the source in the standard X-ray band was detected with RXTE (Atel #265).

A1744-361 was discovered in outburst with Ariel V in February 1976 (IAUC # 2926 ) and was suspected to be an X-ray nova due to rather a long period of activity (~2 months) and a soft X-ray spectrum (Carpenter et al. ApJ, 1977, 179, 27P). The second outburst was detected with RXTE in November-December 2003 (Atel #204). The current INTEGRAL and RXTE detections may mean that the source is at the beginning of its third large outburst.

INTEGRAL is continuing to observe this region. The hard X-ray activity of X-ray novae is often accompanied by an increase in IR and radio flux. We encourage follow-up observations of this source at other wavelengths.