Asteroseismology from space: The δ Scuti star θ² Tauri monitored by the WIRE satellite

Abstract

Abstract. The bright variable star θ2 Tau was monitored with the star camera on the Wide-Field Infrared Explorer satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks: both procedures strengthened our confidence in the results. All the frequencies are in the range 10.8-14.6 cd −1 . The histogram of the frequency spacings shows that 81% are below 1.8 cd −1 ; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 µmag). The rms residual is about two times lower than that usually obtained from successful groundbased multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.

Multiple frequencies of 0² Tau: Comparison of ground-based and space measurements

“…The power spectrum of the WIRE residuals shows a peak at 13.83 cd −1 (see Fig. 6 of Poretti et al 2002) and is therefore probably also present in that data set.…”

“…This remarkable, pioneering study from space led to the discovery of 12 independent frequencies of pulsation down to the 0.5 mmag level (Poretti et al 2002). The satellite data are free of the 1 cd −1 aliasing often present in ground-based data, but include aliasing at the orbital frequency of 15 cd −1 .…”

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AbstractThe satellite photometry of the δ Scuti star θ 2 Tau obtained with the WideField Infrared Explorer (WIRE) led to the detection of 12 frequencies of pulsation (Poretti et al 2002). We examine the available ground-based photometry in the literature to check whether these frequencies are also present.

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The study of pulsating stars from the COROT exoplanet field data

“…The WIRE data of β Crucis have clearly indicated that more modes are excited than thought up to now from ground-based photometry in this β Cep star (Cuypers et al 2002). This is also the case for the δ Scuti star θ 2 Tauri (Poretti et al 2002). Taking these recent results into account we have selected 10 frequencies out of the pool of observed frequencies for the two classes of stars for our simulation.…”

“…The long time base of the data of the latter mission already allowed the discovery of thousands of new periodically variable stars, despite the relatively poor sampling . This led to the publication of the HIPPARCOS catalogue of periodic variable stars (van Leeuwen et al 1997, Grenon et al 1997.…”