Simultaneous time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072^*

¹ Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
² Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
³ Sternwarte der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Corresponding author: S. Falter, falter@sternwarte.uni-erlangen.de

Received: 11 December 2002
Accepted: 15 January 2003

Abstract

We present time-series spectroscopy and multi-band photometry of the sdBV PG 1605+072 carried out simultaneously at the Calar Alto 2.2-m and 3.5-m telescopes. The periodogram analysis of the radial velocity curves reveals three frequencies at 2.078, 2.756, and 1.985 mHz for and at 2.076, 2.753, and 1.978 mHz for . The corresponding radial velocity amplitudes are 12.7, 8.0, and 7.9 km s^-1 for and 14.3, 6.5, and 7.2 km s^-1 for . Furthermore, we found five frequencies that are present in all wavelength bands of the BUSCA photometer. The frequencies detected in the radial velocity curves are recovered by the photometric measurements. Moreover, additional frequencies were present in the periodograms which could not be identified in all four bands simultaneously. The comparison of the amplitudes presented here with previous results from radial velocity and photometric observations of PG 1605+072 shows a significant change or even switch in the power of the modes within short time scales, i.e. about one year. No changes in frequency were registered and the phases of the modes show no wavelength dependency within our multi-band photometry.