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| Paper: |
Theta Tucanae, A Multiperiodic delta scuti Star in an Enigmatic Close-Binary System |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
477 |
| Authors: |
Sterken, C.; De Mey, K. |
| Abstract: |
Eight sets of photoelectric V data for 44 Tau obtained by various researchers between 1965-1996 were collected and analyzed in order to inspect the behaviour of its seven pulsational periods due to stellar evolution. The values of the frequencies given by Poretti et al. (1992, A&A 256, 113) were taken into consideration and used as adjustable parameters in the analysis. With the present study it is shown that the periods of the four modes increase which is in accordance with the theoretical expectations (at least the sign is correct) though the rates are three orders of magnitude greater, while the signs of the period changes are negative for the other three periods. As is the case for HR 8851, which has been submitted very recently for publication, the observed amounts of dP/Pdt for the pulsational periods of 44 Tau are again exceptionally high, while the term dP/Pdt due to stellar evolution in the lower part of the Cepheid instability strip is theoretically expected to be between 10-10/year in the main sequence to 10-7/year for the longer period variables. The increasing number of such examples (see Rodriguez et al., 1995, A&A 299, 108) confirms the suspicions of some earlier authors (see, for example, Breger, 1992, Comm. in Asteroseismology, No. 47, and the references therein) that stellar evolution must not be regarded the only cause of the observed period changes. |
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