INTEGRAL detection of a hard X-ray transient in NGC 6440

E. Kuulkers*, E. Bozzo, A. Bazzano, V. Beckmann, T. Bird, A. Bodaghee, J. Chenevez, M. Del Santo, A. Domingo, P. Jonker, P. Kretschmar, A. Paizis, K. Pottschmidt, C. Markwardt, C. Sanchez-Fernandez, R. Wijnands

*Corresponding author for this work

Research output: Other contributionNet publication - Internet publicationResearch

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Abstract

Referred to by ATel #: 7106, 7136, 7183
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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.
Original languageEnglish
Publication date18 Feb 2015
Publication statusPublished - 18 Feb 2015
SeriesThe Astronomer's telegram
NumberATel #7098

Keywords

  • Binary
  • Globular Cluster
  • Neutron Star
  • Transient
  • Variables
  • Pulsar

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