XMM-Newton observations of the Small Magellanic Cloud: XMMU J004814.1-731003, a 25.55 s Be/X-ray binary pulsar^*

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: fwh@mpe.mpg.de
² University of Maryland, Baltimore County; X-ray Astrophysics Laboratory, Mail Code 662, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 8 February 2008
Accepted: 6 March 2008

Abstract

Aims. To investigate candidates for Be/X-ray binaries in the Small Magellanic Cloud (SMC), we observed a region around the emission nebula N19 with XMM-Newton in October 2006.

Methods. We analysed the EPIC data of the detected point sources to derive their spectral and temporal characteristics.

Results. We detected X-ray pulsations with a period of 25.550(2) s from the second-brightest source in the field, which we designate XMMU J004814.1-731003. The X-ray spectrum is well modelled by a highly absorbed (N_H = 5   cm^-2) power-law with photon index . The precise X-ray position allows us to identify a Be star as the optical counterpart. XMMU J004814.1-731003 is located within the error circle of the transient ASCA source AX J0048.2-7309, but its position is inconsistent with that of the proposed optical counterpart of AX J0048.2-7309 (the emission line star [MA93] 215). It remains unclear if XMMU J004814.1-731003 is associated with AX J0048.2-7309. XMMU J004814.1-731003 might be identical to an RXTE pulsar that was discovered with a period of 25.5 s, but which is listed as a 51 s pulsar in the recent literature.