Discovery of the Slowest X-Ray Pulsar in the SMC, AX J0049.5–7323, with ASCA

Abstract

Abstract The discovery of coherent pulsations with ASCA from an X-ray source, AX J0049.5−7323, is reported. The barycentric period was determined to be 755.5 ± 0.6 s, which is the longest among X-ray pulsators in the SMC. The X-ray spectrum has been found to be unchanged through ASCA observations, with a photon index of ∼ 0.8 and a luminosity of ∼ 5 × 1035 erg s−1 (0.7−10 keV). Archival data of the Einstein and the ROSAT satellites indicate that the flux has been ≲ 10−12 erg s−1 cm−2 (≲ 5 × 1035 erg s−1) for over 20 years and exhibits a variability with a factor of ≳ 10. We argue that AX J0049.5−7323 is an X-ray pulsar with a Be star companion.