2005A&A...442.1015K

We report the detection of pulsations in the far ultraviolet (FUV) light curves of PG1219+534, PG1605+072 and PG1613+426 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) in time-tagged mode (TTAG). Exposures of the order of a few ksec were sufficient to observe the main frequencies of PG1219+534 and PG1605+072 and confirm the detection of a pulsation mode at the surface of PG1613+426 as reported from ground. For the first time we derive time-resolved spectroscopic FUSE data of a sdB pulsator (PG1605+072) and comment on its line profile variation diagram (lpv diagram). We observe the phase shift between the maximum luminosity and the maximum radius to be consistent with the model of an adiabatic pulsator. We also present evidence that the line broadening previously reported is not caused by rotation but is rather an observational bias due to the rapid Doppler shift of the lines with 17km/s amplitude. Thus our observations do not support the previous claim that PG1605+072 is (or will evolve into) an unusually fast rotating degenerate dwarf. These results demonstrate the asteroseismological potential of the FUSE satellite which should be viewed as another powerful means of investigating stellar pulsations, along with the MOST and COROT missions.