INTEGRAL observations of the Small Magellanic Cloud

Abstract

The first INTEGRAL observations of the Small Magellanic Cloud (SMC) (carried out in 2003) are reported in which two sources are clearly detected. The first source, SMC X-1, shows a hard X-ray eclipse and measurements of its pulse period indicate a continuation of the long-term spin-up now covering approximately 30 years. The second source is likely to be a high-mass X-ray binary, and shows a potential periodicity of 6.8 s in the Imager on Board INTEGRAL Satellite lightcurve. An exact X-ray or optical counterpart cannot be designated, but a number of proposed counterparts are discussed. One of these possible counterparts shows a strong coherent optical modulation at ∼2.7 d, which, together with the measured hard X-ray pulse period, would lead to this INTEGRAL source being classified as the fourth known high-mass Roche lobe overflow system. © 2007 The Authors.