δ Scuti stars in Praesepe

II. The STACC 1998 campaign – The spectroscopy

¹ Institute for Physics and Astronomy, University of Aarhus, Universitetsparken, Bygn. 520, 8000 Aarhus C, Denmark
² Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain
³ Thüringer Landessternwarte, 07778 Tautenburg, Germany
⁴ Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India
⁵ Department of Geoscience, National Defence Academy, Yokosuka, Kanagawa 239-8686, Japan
⁶ Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Wien, Austria
⁷ National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
⁸ Okayama Astrophysical Observatory, National Astronomical Observatory, Kamogata, Okayama 719-0232, Japan
⁹ Department of Earth and Planetary Sciences, Kobe University, Kobe, Japan
¹⁰ Lockheed Martin, 3251 Hannover St. L3-29 B201, Palo Alto, CA94304, USA

Corresponding author: T. H. Dall, tdall@ifa.au.dk

Received: 29 May 2001
Accepted: 28 January 2002

Abstract

We present the results of a large international spectroscopic campaign on the δ Scuti star BN Cnc. Combining observations from five observatories taken over more than two weeks, we calculate line indices of the Hα line. A line index is the integrated line flux in a software filter divided by the continuum flux. We demonstrate that this can be used in combination with simultaneous photometry to classify the oscillation modes. We recover all the frequencies also found from photometry and assign likely mode identifications, which differ slightly from previously published values, but are found to be consistent with simple models. The difference in identification is found to have very little effect on the derived luminosity and temperature.