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

¹ Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy
² Department of Physics, 2354 Fairchild Drive, US Air Force Academy, CO 80840, USA
³ SIRTF Science Center, California Institute of Technology, MS 314-6, Pasadena, CA 91125, USA
⁴ Interferometry Science Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125, USA
⁵ Infrared Processing and Analysis Center, California Insitute of Technology, MS 100-22, Pasadena, CA 91125, USA

Corresponding author: E. Poretti, poretti@merate.mi.astro.it

Received: 16 October 2001
Accepted: 7 November 2001

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 ground–based multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.