Communications in Asteroseismology Volume 142 December, 2002 16th Delta Scuti Star Newsletter for Delta Scuti, Gamma Dor and SX Phe stars Editor: Michel Breger, TurkÄ enschanzstra¼e 17, A - 1180 Wien, Austria Layout and Production: Wolfgang Zima Editorial Board: Gerald Handler, Don Kurtz, Jaymie Matthews, Ennio Poretti http://www.deltascuti.net COVER ILLUSTRATION: Instability domains in the upper part of the Hertzsprung-Russel Diagram. Slowly Pulsating B stars are unstable only to nonradial high-order gravity modes. A similar instability was found for massive stars in addition to the ¯ Cep{type instability. For the classical instability strip, only the Blue Edge is shown. A few evolutionary tracks for the indicated values of M=M¯ are shown. The location of γ Dor variables and of stars with solar-like oscillation is also shown. The position of the present Sun is marked by the symbol ¯. For more information please see the article by A. A. Pamyatnykh on p. 10. British Library Cataloguing in Publication data. A Catalogue record for this book is available from the British Library. All rights reserved ISBN 3-7001-3137-2 ISSN 1021-2043 Copyright °c 2002 by Austrian Academy of Sciences Vienna Contents Editorial 4 First results from a multisite campaign on AV Cet by T. H. Dall, G. Handler, and M. B. Moalusi 6 Comments on the upper main-sequence instability domains by A. A. Pamyatnykh 10 A ¯ve-month multitechnique, multisite campaign on the ¯ Cephei star º Eridani by G. Handler & C. Aerts 20 1994 multisite photometry of the ± Scuti star θ2 Tau by M. Breger, W. Zima, R. Garrido, G. Handler, P. Reegen, R. Zechner 25 Solar-like oscillations in ± Scuti stars by R. Samadi, M.-J. Goupil, and G. Houdek 37 NOTES Fishing for Delta Scuti stars in the Hipparcos photometric database by J. R. Percy & G. Gilmour-Taylor 48 Discovery of pulsation in the Am Star HD 102480 by S. Joshi, V. Girish, R. Sagar, D. W. Kurtz, P. Martinez, and S. Seetha 50 Multiperiodicity of V350 Peg by J. Vidal-S¶ainz, P. Wils, P. Lampens, and E. Garc¶³a-Melendo 52 The High Amplitude ± Scuti Variable Star GSC 3109-00162 by P. Wils, P. Van Cauteren, and R. Groenendaels 54 Is TU UMi a W UMa-type system? by A. Rolland, V. Costa, E. Rodr¶³guez, P.J. Amado, J.M. Garc¶³a-Pelayo, P. L¶opez de Coca, and I. Olivares 57 CCD photometry of XX Cyg by S. N. Udovichenko 61 Comm. in Asteroseismology Vol. 142, 2002 Editorial This is no empty bag! During the last decade, Asteroseismology has grown to a level where the customary, wonderful informal contacts between di®erent workers in a small ¯eld are no longer enough to stay organized. So, why not bundle our expertise in a more organized way, apply for ¯nancial assistance that individuals could only dream about, and use some of these funds to support young scientists and allow them to move between di®erent groups? And to be a bit sel¯sh, why should you have to reinvent the wheel in your own country in your attempts to try to persuade the various funding agencies that asteroseismology is an important astronomical ¯eld? The supporting sci- enti¯c arguments used in your proposal have already been written down several times by your colleagues in other countries. It appears that a loose association of asteroseismologists needs to be formed to support these and many other common interests. Enter BAG, the Belgian Asteroseismology Group. Do not be misled by the unassuming name! Under the leadership of Conny Aerts, in October, this group invited representatives from di®erent institutions to Leuven in order to plan an Asteroseismology Society and to write a joint proposal to the EU to establish a European Network of Excellence in Asteroseismology (ENEAS). The meeting was a smashing success with a high level of science. The discussions on details of new committees and o±ces and how the o±ces are to be ¯lled were kept to a minimum. Such (necessary) discussions make people like me turn and run away fast. Conny divided the time beautifully. Since the chances of obtaining EU ¯nancing for the ENEAS proposal to the EU regrettably are small, the formation of an asteroseismological society to assist the scientists may turn out to have the largest long-term impact. What does this editorial on the organization of the asteroseismologists have to do with a Delta Scuti Newsletter? I may be biased in this matter, I admit. But the growth in our knowledge of the behaviour of Delta Scuti and related stars has been almost exponential during the last decades. Due to this work, Delta Scuti stars form one of the main areas in asteroseismology. Furthermore, it appears that every discovery of a new type of pulsating variable in the end leads to the same unsolved astrophysical questions such as mode selection, amplitude and period variability. The answers to these scienti¯c questions may Editorial 5 come from selecting the suitable pieces of the puzzle from many di®erent types of stars. Successful asteroseismology means many types of stars, from solar-type all the way to the hot PG 1159 stars.......... We hope that you ¯nd this issue of the newsletter interesting. The next volume of the Communications will again be devoted to all aspects of astero- seismology. So keep the news and articles coming! Michel Breger Editor Comm. in Asteroseismology Vol. 142, 2002 First results from a multisite campaign on AV Cet T. H. Dall1, G. Handler2;3, M. B. Moalusi4 1 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago, Chile 2 Institut furÄ Astronomie, TurkÄ enschanzstrasse 17, 1180 Vienna, Austria 3 South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa 4 Department of Physics, University of the North-West, Private Bag X2046, Mmabatho 2735, South Africa Abstract We present the ¯rst results from an international observing campaign on the ± Scuti star AV Cet. From more than 80 hours of StrÄomgren photometry, not yet fully analysed, we ¯nd 8 frequencies between 14 d¡1 and 31 d¡1, with amplitudes between 4.4 mmag and 1.6 mmag. Among the detected frequencies are the three that were found in previous studies. Results from simultaneous spectroscopy will be used in a later paper to attempt mode identi¯cation of the strongest modes of AV Cet. Introduction Little work has been done on the star AV Cet (HD 8511, V=6.21, F0V) since it was recognized as a ± Scuti pulsator by J¿rgensen et al. (1971). Based on four nights of photoelectric observations Gonzalez-Bedolla (1990) and Gonzalez- Bedolla et al. (1990) found one dominant frequency of 14:59 d¡1 and a sus- pected second frequency of 19.19 d¡1. Later Dall & Frandsen (2002) veri¯ed the frequencies and found evidence for an additional frequency around 33 d¡1 in the line indices of the Balmer lines, based on only four hours of spectroscopy. In order to verify this star as a multimode pulsator and to clarify its pulsa- tional content an international photometric campaign was launched in October 2001, involving sites in Chile, South Africa and Australia. Regrettably we were unable to obtain data from Australia due to dome repair works that took much longer than expected. The observing log is presented in Table 1. T. H. Dall, G. Handler, and M. B. Moalusi 7 Observatory Telescope StrÄomgren hours HJD { 52200 ¯lters observed ESO, La Silla 0.5m SAT uvby 41.5 8,11,12,13,14,15 SAAO 0.5m vby 42.2 8,9,12,13,14,15,16,18 Table 1: The participating sites and the amount of time used. Alongside the photometric campaign, spectroscopy was done with the Dan- ish 1.54m at La Silla, Chile. We will attempt mode identi¯cation by comparing the same modes in photometry and Balmer-line-indices, as has been done for FG Vir (Viskum et al. 1998) and BN Cnc (Dall et al. 2002). The spectroscopic data and part of the photometric data are still undergoing analysis, so here we will only present preliminary results of the photometric campaign. Data analysis and results The raw data from La Silla was fed through the standard reduction pipeline developed by E. H. Olsen et al. at the Copenhagen University Observatory, while the data from South Africa was locally reduced in the standard way. So far, only the StrÄomgren y data has undergone frequency analysis. The data set was assigned statistical weights based on the local scatter in the time series with each sub-series, de¯ned by observatory and date, treated individually. The frequency analysis was done using Period98 (Sperl 1998), which yielded the amplitude spectrum of the combined y data set shown in Fig. 1. The frequency content of AV Cet is given in Table 2. mode frequency amplitude S/N [d¡1] [mmag] f1 15.90 4.4 19 f2 14.59 2.6 11 f3 28.16 2.1 8.9 f4 25.95 2.0 8.5 f5 30.83 1.7 7.2 f6 29.39 1.6 6.8 f7 16.36 1.6 6.8 f8 21.20 1.6 6.8 Table 2: The frequencies found in the combined StrÄomgren y data set of AV Cet. The frequency spectrum after prewhitening with f1{f8 shows excess power, but we prefer not to present any more frequencies before the full data set has been analysed. 8 First results from a multisite campaign on AV Cet Figure 1: The amplitude spectrum of the combined y data set is shown in the bottom panel, with the window shown in the top panel.