Serpens X-1 observed by INTEGRAL^*

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica - Sezione di Bologna, CNR, via Gobetti 101, 40129 Bologna, Italy e-mail: masetti@bo.iasf.cnr.it
² NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA
³ Joint Center for Astrophysics, Department of Physics, University of Maryland, Baltimore County, MD 21250, USA
⁴ Danish Space Research Institute, 2100 Copenhagen 0, Denmark
⁵ Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Palermo, CNR, via La Malfa 153, 90146 Palermo, Italy
⁶ CEA Saclay, DSM, DAPNIA, Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex, France
⁷ Dipartimento di Fisica, Università di Ferrara, via Paradiso 12, 44100 Ferrara, Italy
⁸ N. Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland

Received: 5 February 2004
Accepted: 11 May 2004

Abstract

Here we report results of an INTEGRAL-AO1 observation of the X-ray burst and atoll source Ser X-1 performed in May 2003. The object was observed for a total on-source time of 400 ks but nearly 8° off-axis due to its amalgamation with an observation of SS 433, the pointing target source. Ser X-1 has been clearly detected up to 30 keV with unprecedented positional accuracy for high-energy emission. The 20–30 keV light curve showed substantial variability during the observation. Comparison with previous observations indicates that the source was in its high (“banana”) state and displayed a soft spectrum during the INTEGRAL pointing. A (non simultaneous) radio-to-γ-rays broad-band spectral energy distribution is also presented for the first time and discussed.