37 (12+/-2 mCrab, 6 sigma). Earlier observations on 20 Aug 23:37 - 21 Aug 03:19 do not show any source activity, with a 3-sigma upper limit of 7 mCrab (20-40 keV). By combining the three observations when the source is detected, we obtain a detection significance of 9.4 and 7.0 sigma in the 20-40 keV and 40-80 keV energy bands, respectively. The average ISGRI spectrum can be well described (reduced chi^2 of 0.8 for 8 degrees of freedom) by a simple power-law of index 2.1+/-0.5 (uncertainty at 68% c.l.) and a 20-80 keV flux of 9.8e-11 erg/s/cm^2. The best-determined position with a 90% confinement radius of 2.8 arcmin (Gros et al., 2003, A&A, L179) is (RA,DEC)=(262.172,-29.325), fully consistent with the location of the Swift/XRT Soft X-ray counterpart (ATel #2824). IGR J17285-2922 was not detected by JEM-X with a 3-sigma upper limit of about 12 mCrab (3-11 keV). This is consistent with the peak flux of 6.5 mCrab obtained for XTE J1728-295 in the 2-10 keV band with RXTE/PCA (ATel #2823). We note that the hard X-ray activity is confirmed by the Swift/BAT Hard X-ray Transient Monitor (see ATel #904), which evidences enhanced emission around the same time, and at a similar level. The coincidence of the renewed low-level activity of IGR J17285-2922 in the hard X-rays with the reported X-ray outburst of XTE J1728-295 (ATel #2823) and the positional coincidence with the proposed Soft X-ray counterpart (ATel #2824) strengthen the suggestion that the two sources are actually the same object. The next INTEGRAL Galactic bulge monitoring observation is foreseen to start at UT 4 Sep 2010 11:26.
|Journal||The Astronomer's telegram|
|Publication status||Published - 2010|