Research Note

INTEGRAL and Swift/XRT observations of IGR J16460+0849

¹ Laboratory for Particle Astrophysics, Institute of High Energy Physics, Beijing 100049, PR China e-mail: szhang@mail.ihep.ac.cn
² Theoretical Physics Center for Science Facilities (TPCSF), CAS, PR China
³ Center for Astrophysics, Tsinghua University, Beijing 100084, PR China

Received: 27 August 2008
Accepted: 19 January 2009

Abstract

Aims. IGR J16460+0849 is reported in the 3rd IBIS catalog with the shortest exposure of about 11 ks among all the detected sources, which makes it the most interesting target to be investigated with a deeper exposure. The currently available data have increased to an exposure time of a few hundred ks. This stimulates us to investigate the source again by using all the available data.

Methods. We analyze all available observations carried out by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) on the unidentified source IGR J16460+0849. The data were processed by using the latest version OSA 7.0. In addition we analyze also all the available Swift/XRT data on this source.

Results. We find that IGR J16460+0849 has a detection significance of ~4.4σ in the 20-100 keV band during the observational period between March 2003 and September 2004, when it was exposed by ~19 ks. Thereafter the source was not detected anymore, despite an additional exposure of ~271 ks. This suggests a flux variability on a timescale of years. The spectral analysis shows that the IBIS/ISGRI data are well presented by a power-law shape, with a photon index obtained as 1.45 ± 0.86. So far, the source has been detected consistently by IBIS/ISGRI in the subsequent observations and in the adjacent energy bands. We have analyzed the Swift/XRT observations on IGR J16460+0849 as well, and found no source inside the IBIS/ISGRI error circle. The non-detection during the Swift/XRT observation is consistent with the source having a variable nature.