Detection of a 522 s Pulsation from the Transient X-ray Source Suzaku J0102.8--7204 (SXP 523) in the Small Magellanic Cloud

TL;DR

This paper reports the discovery of a 522-second pulsation from a transient X-ray source in the Small Magellanic Cloud, identifying it as a high-mass X-ray binary pulsar with a Be star companion.

Contribution

The study provides the first detection of a pulsation from this transient source and characterizes its spectral and temporal properties, confirming its nature as a Be star high-mass X-ray binary.

Findings

Detected a 522.3 s pulsation in the X-ray source.

Spectral analysis shows a power-law spectrum with photon index ~1.0.

Identified the source as a Be star high-mass X-ray binary.

Abstract

During a routine calibration observation of 1E0102.2-7219 in the Small Magellanic Cloud (SMC) carried out in October 2012 for the Suzaku satellite, we detected a transient X-ray source at (RA, Dec) = (01h02m47s, -72d04m54s) in the equinox J2000.0 with a positional uncertainty of ~1"4. We conducted a temporal and spectral analysis of the source and found a coherent pulse signal with a period of 522.3 +/- 0.1 s, and a featureless spectrum described by a single power-law model with a photon index of 1.0 +/- 0.1 and a 0.5-10 keV luminosity of 8.8 x 10^35 erg s^-1 at an assumed distance of 60 kpc. The Suzaku source is likely to be the counterpart of 2XMMJ010247.4-720449, which has been observed several times, including during outburst by Swift. Based on the X-ray characteristics in our data, as well as the transient record and optical and near-infrared features in the literature, we conclude that this source is a high-mass X-ray binary pulsar with a Be star companion in the SMC, which is known to harbor an exceptionally large (80) number of such sources in comparison to our Galaxy.