Pulsation of the δ Scuti star θ2 Tau: New multisite photometry and modelling of instability

DOI: 
10.1046/j.1365-8711.2002.05734.x
Publication date: 
11/10/2002
Main author: 
Breger M.
IAA authors: 
Garrido R.
Authors: 
Breger M., Pamyatnykh A.A., Zima W., Garrido R., Handler G., Reegen P.
Journal: 
Monthly Notices of the Royal Astronomical Society
Publication type: 
Article
Volume: 
336
Pages: 
249-258
Number: 
Abstract: 
The results of a multisite photometric campaign of θ2 Tau are reported. This binary system consists of an evolved and a main-sequence A star, both situated inside the instability strip. The 12th Delta Scuti Network campaign included 152 h of high-precision photometry obtained at four observatories. This leads to the derivation of 11 frequencies of pulsation in the 10.8 to 14.6 cycle d-1 range. These frequencies confirm the results from previous Earth-based (1982-1986) as well as satellite (2000) photometry, although amplitude variability on a time-scale of several years is present. We show that at least two high frequencies (26.18 and 26.73 cycle d-1) are also present in θ2 Tau. Arguments are given that these high frequencies originate in the main-sequence companion and are not combination frequencies, fi + fj, from the primary. Models for both the primary and the secondary components were checked for the instability against radial and non-radial oscillations. All hot models of the primary with Teff > 8000 K are stable in the observed frequency range. The best fit between the theoretical and observed frequency ranges is achieved for models with Teff ≈ 7800 K (or slightly higher), in agreement with photometric calibrations. The instability range spans two or three radial orders in the range p4 to p6 for radial modes. Post-main-sequence models (with or without overshooting) are preferable for the primary, but main-sequence models with overshooting cannot be excluded. For the less-luminous secondary component the instability range is wider and spans 5 to 7 radial orders from p2 to p8. The observed frequencies lie around radial modes p5 to p6. The main uncertainties of these results are caused by a simple treatment of the convective flux in the hydrogen ionization zone.
Database: 
WOK
SCOPUS
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2002MNRAS.336..249B/abstract
ADS Bibcode: 
2002MNRAS.336..249B
Keywords: 
δ Scuti; Stars: individual: θ2 Tau; Stars: individual: 78 Tau; Stars: oscillations; Techniques: photometric