IGR J17252-3616: an accreting pulsar observed by INTEGRAL and XMM-Newton

¹ INTEGRAL Science Data Centre, Ch. d'Écogia 16, 1290 Versoix, Switzerland e-mail: Juan.Zurita@obs.unige.ch
² Observatoire de Genève, Ch. des Maillettes 51, 1290 Sauverny, Switzerland
³ IASF-INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁴ Dipartimento di Astronomia, Universita degli Studi di Bologna, via Ranzani 1, I40127 Bologna, Italy
⁵ Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, BP 4346, 31028 Toulouse Cedex 4, France
⁶ Service d'Astrophysique, DAPNIA/DSM/CEA, 91191 Gif-sur-Yvette, France
⁷ School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ, UK
⁸ IASF/CNR, via Piero Gobetti 101, 40129 Bologna, Italy

Received: 21 July 2005
Accepted: 25 September 2005

Abstract

The discovery of the X-ray source IGR J17252-3616 by INTEGRAL was reported on 9 February 2004. Regular monitoring by INTEGRAL shows that IGR J17252-3616 is a persistent hard X-ray source with an average count rate of 0.96 counts (~6.4 mCrab) in the 20–60 keV energy band. A follow-up observation with XMM-Newton which was performed on March 21, 2004, showed that the source is located at RA (2000.0) = and Dec = with an uncertainty of . The only infra-red counterpart to be found within the XMM-Newton error circle was 2MASS J17251139-3616575, which has a Ks-band magnitude of 10.7 and is located 1″ away from the XMM-Newton position.
The analysis of the combined INTEGRAL and XMM-Newton observations shows that the source is a binary X-ray pulsar with a spin period of 413.7 s and an orbital period of 9.72 days. The spectrum can be fitted with a flat power law plus an energy cut off () or a Comptonized model (). The spectrum also indicates a large hydrogen column density of suggesting an intrinsic absorption. The Fe Kα line at 6.4 keV is clearly detected. Phase-resolved spectroscopy does not show any variation in the continuum except the total emitted flux. The absorption is constant along the pulse phase. This source can be associated with EXO 1722-363 as both systems show common timing and spectral features. The observations suggest that the source is a wind-fed accreting pulsar accompanied by a supergiant star.