Two active X-ray transients in the Galactic Center region as seen by INTEGRAL

The first of a new series of INTEGRAL Galactic bulge monitoring observations (ATel #438, #874) performed between UT 2007, Feb 15 18:35 and 22:17 shows two transient X-ray sources to be active in the Galactic Center region. One is the recently found source IGR J17453-2853 at RA, Dec (Degrees) = 266.32, -28.89, with a 90% confidence error region of 2 arcmin (Kuulkers et al. 2007, A&A, in press, astro-ph/0701244).

The IBIS/ISGRI 20-60 keV flux was about 11 mCrab, with a detection significance of 8. It is not detected in the JEM-X 3-10 and 10-25 keV bands with upper limits of about 5 mCrab in both bands. This source was last seen to be active at similar flux levels between 2005, April 3 and 14. As noted by Kuulkers et al. (2007), if the non-detection with JEM-X is due to absorption in the line of sight, N_H should be larger than about 10^23 atoms per cm^2.

The other source is detected with JEM-X at RA, Dec (Degrees) = 266.40, -29.05, with a 90% confidence error region of 2 arcmin. There are various known X-ray transients within the error circle, such as Swift J174535.5-290135.6 (e.g., ATel #753, #756) or CXOGC J174535.5-290124 (e.g., ATel #753, #892).

It is detected at about 22 mCrab in 3-10 keV, with a detection significance of 14. The source is clearly variable on a 15-minute time scale. It is not detected in the JEM-X 10-25 keV band with an upper limit of about 5 mCrab. Follow-up observations with more position sensitive instruments are needed to pin-point the exact origin of the transient X-ray emission.