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INTEGRAL serendipitous hard X-ray detection of the millisecond pulsar HETE J1900.1-2455

ATel #590; P. Goldoni (APC & SAp/CEA-Saclay, France), S. Soldi (ISDC, Geneva), S. E. Shaw (Southampton UK/ISDC, Geneva), M. Cadolle Bel (APC & SAp/CEA-Saclay, France), P. Laurent (APC & SAp/CEA-Saclay, France), M. Falanga (APC & SAp/CEA-Saclay, France), A. Goldwurm (APC & SAp/CEA-Saclay, France), P. Ubertini (INAF/IASF Rome Italy)
on 23 Aug 2005; 08:10 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Paolo Goldoni (pgoldoni@cea.fr)

Subjects: X-ray, Gamma Ray, Request for Observations

We report the serendipitous detection with the IBIS/ISGRI detector of the millisecond pulsar HETE J1900.1-2455 (ATEL #516) during the INTEGRAL ToO observations of XTE J1818-245 in the Galactic Center Region from 2005-08-20 10:00:00 (UTC) until 2005-08-21 06:38:23 (UTC). HETE J1900.1-2455 was at a distance between 7 and 14 degrees from the pointing direction and it is clearly detected in the 20-40 and 40-80 keV energy bands with significance levels of 26 and 13 sigma, respectively. This correspond to a source flux of ~37 mCrab (20-40 keV) and ~32 mCrab (40-80 keV). We remark that the source is stronger than previously reported (ATEL #525), which supports a new period of activity after the June 2005 outburst unlike what has been observed in the other accreting millisecond pulsars. This renewed activity has also been suggested by the recent Swift detection on August 17 2005 of a soft burst from HETE J1900.1-2455 (Barbier et al., GCN 3824).