INTEGRAL detects hard X-rays from SAX J1810.8-2609 during its current outburst

ATel #1185; P. Haymoz. D. Eckert (ISDC, Switzerland), S. Shaw (Southampton, UK/ ISDC, Switzerland) & E. Kuulkers (ESA/ESAC, Spain) on behalf of the INTEGRAL Galactic Bulge Monitoring Group
on 20 Aug 2007; 11:03 UT
Credential Certification: Nami Mowlavi (Nami.Mowlavi@obs.unige.ch)

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We report on the detection of the neutron star transient LMXB SAX J1810.8-2609 with the IBIS/ISGRI X-ray imager on board INTEGRAL. Following reports of renewed activity from this object (GCN 6706 and 6707), observations with the XRT telescope on board Swift on Aug. 6-9 confirmed that the source was brightening (ATel #1175). On Aug. 19, INTEGRAL performed a 13 ksec monitoring observation of the Galactic bulge region. The source was detected by ISGRI in the 20-40 keV band with a flux of (2.1 +/- 0.1)E-10 erg/cm2/s (45 mCrab) at a confidence level of 21 sigma. The source was also detected in the 40-80 keV band with a flux of (1.3 +/- 0.2)E-10 erg/cm2/s (27 mCrab). Unfortunately, the source was always outside the JEM-X field of view, so direct comparison with the XRT flux is not possible. However, the relatively high flux found in ISGRI data at higher energies seems to confirm that the source is still brightening. Preliminary spectral analysis reveals a photon index of ~2.6, which is slightly steeper than the index reported from the Swift observation at lower energies (~2). INTEGRAL will observe the field again on Aug. 22, 2007 and approximately every 3 days after that as a continuation of the INTEGRAL Galactic Bulge Monitoring observation (ATel #1005). We encourage follow-up observations of the source at other wavelengths.