The discovery of 96 s pulsations from the variable X-ray source 1SAX J0544.1-710 in the Large Magellanic Cloud

We report the discovery of a ∼ 96 s period X-ray pulsar in the direction of the Large Magellanic Cloud (LMC). The BeppoSAX X-ray spectrum is well fitted by an absorbed power-law model with photon index ∼ 0.5. The unabsorbed luminosity in the 2-10 keV energy range is ∼ 9×1035 erg s−1. The BeppoSAX position (40′′ uncertainty radius) of 1SAX J0544.1710 was found to be consistent with that of the ASCA source AX J0448-70.4 and WGACAT (ROSAT PSPC) source 1WGA J0544.1-710. The source was detected four times between 1991 and 1996 at luminosity levels from ∼ 3 × 1035 to 9 × 1035 erg s−1 (2-10 keV), while during a relatively deep ROSAT HRI observation an extrapolated 2-10 keV luminosity upper limit of ∼ 1 × 1035 erg s−1 was obtained. Timing analysis of the ASCA data confirmed the BeppoSAX period discovery. Longterm flux variability is evident in the ROSAT and Einstein data. We revealed a pronounced Hα activity from a bright (V ' 15) likely Be-type star within the 8′′ROSAT PSPC error circle. Its optical spectrum shows it is located in the LMC. These results strongly suggest that 1SAX J0544.1-710 is a transient X-ray pulsar in a massive binary system.