An INTEGRAL hard X-ray survey of the Large Magellanic Cloud

Abstract

Two observation campaigns in 2003 and 2004 with the INTEGRAL satellite have provided the first sensitive survey of the Large Magellanic Cloud with an imaging instrument in the hard X-ray range (15 keV-10 MeV). The high energy flux and long-term variability of the black hole candidate LMC X-1 was measured for the first time without contamination by the nearby (~25') young pulsar PSR B0540-69. We studied the accreting pulsar LMC X-4 by constraining the size of the hard X-ray emitting region (≤3 × 10¹⁰ cm) from analysis of its eclipses and by measuring its spin period (13.497 ± 0.005 s) in the 20-40 keV band. As it was in a soft state during the first observation and possibly in an extremely low state in the second one, LMC X-3 was not detected. Thanks to the large field of view of the IBIS instrument, we could also study other sources falling serendipitously in the observed sky region around the LMC: the Galactic low mass X-ray binary EXO 0748-676, the accreting pulsar SMC X-1 in the Small Magellanic Cloud, and the Active Galactic Nucleus IRAS 04575-7537. In addition we discovered five new hard X-ray sources, two of which most likely belong to the LMC.