During INTEGRAL Galactic bulge monitoring (e.g., ATel #438) observations performed on UT 2015 February 17 at 12.53-16:45, IBIS/ISGRI detected renewed activity at hard X-rays from a transient within the Globular Cluster NGC 6440. The best determined position is: RA, Dec (J2000) = 267.208, -20.314 degrees, with an error radius of 2.4 arcmin (90% c.l.). Formally, there is no known X-ray source within the error circle, so we label the source as IGR J17488-2018. The hard X-ray transient is detected at a significance of 11 (6.5) sigma on the IBIS/ISGRI mosaic in the 20-40 keV (40-80 keV) energy band. The IBIS/ISGRI spectrum (total exposure time of 12 ks) provides a photon index of 2.4 +/- 0.5 and a 20-100 keV flux of 4.8E-10 ergs/cm^2/s. NGC 6440 was outside the JEM-X field-of-view for the entire observation. The Globular Cluster NGC 6440 is known to host millisecond X-ray pulsars (see, e.g., ATel #2672), so it is possible that INTEGRAL detected an outburst from one of these sources. We can not rule out that one of the known X-ray sources just outside the error circle (such as MXB 1746-20 aka H1745-203) is experiencing an outburst. Note that Swift/BAT also detects enhanced activity from H1745-203 over the last days. Further INTEGRAL observations in the direction of NGC 6440 are planned for the coming weeks. Swift ToO follow-up observations have been requested. Observations at other wavelengths are encouraged.
|Number of pages||1|
|Publication status||Published - 2015|
|Series||The Astronomer's telegram|
- Globular Cluster
- Neutron Star