High-resolution spectroscopy of the δ Scuti star 44 Tauri: photospheric element abundances and mode identification^*

¹ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: zima@ster.kuleuven.be
² Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Vienna, Austria
³ Thüringer Landessternwarte, 07778 Tautenburg, Germany
⁴ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany

Received: 31 January 2007
Accepted: 28 May 2007

Abstract

Aims.We carried out a detailed spectroscopic study of the δ Sct star 44 Tau to investigate its element abundances and stellar parameters as well as to provide an identification of its non-radial oscillation modes.

Methods.We acquired high-resolution high-signal-to-noise ratio time-series spectroscopy of 44 Tau from two observing sites in Europe during a time span of 30 days. We determined atmospheric element abundances and stellar properties using spectroscopic methods. Due to the low value of  the mode identification was carried out by applying the moment method.

Results.A very low value of the projected rotational velocity of  = 2 ± 1 km s^-1 was determined. We detected spectroscopically 12 independent frequencies between 6.8 and 11.6 d^-1 and four combination frequencies by analyzing the line moments as well as the pixel-intensities across the profiles of carefully selected Fe absorption lines. The mode identification applying the moment method yielded six axisymmetric pulsation modes. Two frequencies are low-degree prograde pulsation modes. A rather low value of log g = 3.6 was determined implying an evolved evolutionary status of 44 Tau. The derived atmospheric element abundances are close to solar.

Conclusions.Our analysis revealed that 44 Tau is an exceptionally slowly rotating δ Scuti star pulsating with a rich spectrum of axisymmetric pulsation modes. This simplifies the seismic modeling since rotational perturbations of higher order can be neglected.