XTE J0111.2 - 7317: A nebula-embedded X-ray binary in the Small Magellanic Cloud

Abstract

The observed characteristics of the nebulosity surrounding the Small Magellanic Cloud (SMC) high-mass X-ray binary XTE J0111.2-7317 are examined in the context of three possible nebular types: supernova remnant, bowshock and H II region. Observational evidence is presented which appears to support the interpretation that the nebulosity surrounding XTE J0111.2-7317 is an H II region. The source therefore appears to be a normal SMC Be X-ray binary (BeXRB) embedded in a locally enhanced interstellar medium which it has photoionized to create an H II region. This is supported by observations of the X-ray outburst seen with the Burst and Transient Source Experiment (BATSE) and Rossi X-ray Timing Explorer (RXTE) in 1998-1999. It exhibited characteristics typical of a giant or type n outburst in a BeXRB including large spin-up rates, L X ≤ 1038 erg cm-2 s-1, and a correlation between spin-up rate and pulsed flux. However, the temporal profile of the outburst was unusual, consisting of two similar intensity peaks, with the first peak of shorter duration than the second.