  The results of a multisite photometric campaign of Theta2 Tau are reported.
This binary system consists of evolved and main-sequence A stars inside the
instability strip. The 12th Delta Scuti Network campaign included 152 hours 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 c/d 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 c/d are also present in Theta 2 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 nonradial oscillations. All hot models of the primary with Teff > 8000K are
stable in the observed frequency range. The best fit between the theoretical
and observed frequency ranges is achieved by models with Teff approximately
equal to 7800K (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.
