EDP Sciences
Free access
Volume 442, Number 3, November II 2005
Page(s) 1015 - 1021
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20052940

A&A 442, 1015-1021 (2005)
DOI: 10.1051/0004-6361:20052940

Time-resolved FUSE photometric and spectroscopic observations: PG 1219+534, PG 1605+072, and PG 1613+426

Kuassivi1, A. Bonanno2 and R. Ferlet3

1  AZimov association 14, rue Roger Moutte, 83270 St Cyr, France
    e-mail: martial.andre@free.fr
2  INAF - Osservatorio Astrofisico di Catania, Citta Universitaria, 5123 Catania, Italy
    e-mail: abo@ct.astro.it
3  Institut d'Astrophysique de Paris, 98 bis Bd Arago, 75014 Paris, France
    e-mail: ferlet@iap.fr

(Received 27 February 2005 / Accepted 22 June 2005 )

We report the detection of pulsations in the far ultraviolet (FUV) light curves of PG 1219+534, PG 1605+072 and PG 1613+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 PG 1219+534 and PG 1605+072 and confirm the detection of a pulsation mode at the surface of PG 1613+426 as reported from ground. For the first time we derive time-resolved spectroscopic FUSE data of a sdB pulsator (PG 1605+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 17 km s-1 amplitude. Thus our observations do not support the previous claim that PG 1605+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.

Key words: instumentation: photometers -- instumentation: spectrographs -- line: profiles -- stars: white dwarfs -- techniques: radial velocities -- stars: oscillations (including pulsations)

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© ESO 2005