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

TL;DR

This study reports the discovery of a 25.55-second pulsar in the Small Magellanic Cloud, identified as a Be/X-ray binary with detailed spectral and timing analysis, contributing to understanding of such systems.

Contribution

First detection and characterization of a 25.55 s Be/X-ray binary pulsar in the SMC using XMM-Newton data, clarifying its properties and potential associations.

Findings

Detected 25.55 s X-ray pulsations from source XMMU J004814.1-731003.

Spectral analysis shows a highly absorbed power-law with photon index ~1.33.

Identified optical counterpart as a Be star, but uncertain association with previous sources.

Abstract

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. We analysed the EPIC data of the detected point sources to derive their spectral and temporal characteristics. 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 (NH = 5x10^22) powerlaw with photon index 1.33+/-0.27. 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 51 s pulsar in the recent literature.