On the nature of the variable star UNSW-V-760

Abstract

The results of multicolour photometric monitoring over several nights of the probable X-ray source UNSW-V-760 are presented. Drawing on both present and past observations, it is shown that the star is multiperiodic and that all the variability can probably be explained by two non-sinusoidal periodicities with periods of 0.276 and 0.198 d. Possible causes (binarity, rotation and oscillation) of the variations are discussed and it is concluded that pulsation must play a role. A classification in the range K1Vke–K3Vke is derived from two low-dispersion spectra. Curiously, the pulsation periods are closer to what is expected for a K giant star, but the amplitudes are two orders of magnitude larger than those seen in K giants.