Photometric Periodicities of Be/X-ray Pulsars in the Small Magellanic Cloud

Abstract

Analysis of the longterm photometric variability of 7 Be/X-ray-pulsar systems in the Small Magellanic Cloud has been carried out. We find a variety of types of variability are present, including: longterm irregular changes, periodic orbital outbursts due to interaction between the stars (weeks to months), low-amplitude quasi-periodic variations of the equatorial disk (days), and nonradial pulsations of the Be primary star (hours). This is the first time nonradial pulsations have been identified in Be/X-ray binaries, although they were previously known in some single Be stars.