Periodic optical outbursts from the Be-neutron star binary AX J0049.4-7323

The optical light curve of the Be - neutron star binary AX J0049.4 - 7323 has been investigated using data from the MACHO and OGLE-II projects. This X-ray source, whose neutron star has a very slow rotation rate (P-pulse = 755.5 s), shows optical outbursts every similar to 394 days. The regularity of these outbursts suggests that their recurrence time is the orbital period of the system. During the outbursts, the system brightens and becomes slightly redder. A possible interpretation is that a portion of the equatorial disk is excited as the neutron star passes through it during periastron passage. In the intervals between outbursts, the light curve shows similar to 11 day quasi-periodic variability, which may be associated with the rotation of the Be star's extended disk.