Discovery of a new X-ray pulsar, AX J0049-729, in the small magellanic cloud with ASCA

We report on the results of two ASCA observations on an X^ray source, AX J0049-729 (= RX J0049.1-7250), in the Small Magellanic Cloud. A sinusoidal pulsation with a barycentric period of 74.676 ± 0.022 s was found. The pulse fraction was ~ 70%, independent of the X-ray energy. The spectrum was hard with an absorbed power-law having a photon index of ~ 1. The X-ray flux was 1.1 × 10-11 erg s-1 cm-2, and then declined to 1.6 × 10~12 erg s-1 cm-2 from the first to the second observations, separated by about one month. Together with the previous results of the Einstein and ROSAT satellites, we found that AX J0049-729 has been in quiescent states, but occasionally showing flare activities. The flux variability, long-pulse period, and hard spectrum support the idea that AX J0049-729 is an X-ray binary pulsar, most likely a Be star binary. © 1999 Astronomical Society of Japan.