The MultiSite Spectroscopic Telescope campaign: 2 m spectroscopy of the V361 Hya variable PG 1605+072

¹ Dr. Remeis-Sternwarte, Astronomisches Institut der Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany e-mail: otoole@sternwarte.uni-erlangen.de
² School of Physics, University of Sydney, NSW 2006, Australia
³ Armagh Observatory, College Hill, Armagh BT61 9DG, UK
⁴ Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
⁵ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
⁶ Department of Physics, University of Nebraska at Omaha, 6001 Dodge St., Omaha NE 68182, USA
⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
⁹ Teoretisk Astrofysik Center, Danmarks Grundforskningsfond, 8000 Aarhus C, Denmark

Received: 2 May 2005
Accepted: 25 May 2005

Abstract

We present results and analysis for the 2 m spectroscopic part of the MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002. The goal of the project was to observe the pulsating subdwarf B star PG 1605+072 simultaneously in velocity and photometry and to resolve as many of the >50 known modes as possible, which will allow a detailed asteroseismological analysis. We have obtained over 150 h of spectroscopy, leading to an unprecedented noise level of only 207 m s^-1. We report here the detection of 20 frequencies in velocity, with two more likely just below our detection threshold. In particular, we detect 6 linear combinations, making PG 1605+072 only the second star known to show such frequencies in velocity. We investigate the phases of these combinations and their parent modes and find relationships between them that cannot be easily understood based on current theory. These observations, when combined with our simultaneous photometry, should allow asteroseismology of this most complicated of sdB pulsators.