Effects of rotation on the colours and line indices of stars 5. The ZRMS and the ZRZAMS |
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Authors: | Annamma Mathew R Rajamohan |
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Institution: | (1) Indian Institute of Astrophysics, 560034 Bangalore |
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Abstract: | The observeduvby and Hα indices of member stars of the Hyades and Praesepe clusters have been analysed in detail for rotation effects. The Alpha
Persei, Pleiades and the Centaurus subgroup of the Scorpio—Centaurus association have been reanalysed using the observed indices
instead of the extinction-corrected indices used earlier. The observed rotation effects from the analysis of these cluster
data are found to be in excellent agreement with the theoretical predictions of Collins & Sonneborn (1977). We have also analysed
the α,c and (u − b) values of the member stars of NGC 1976, 2264, 2287, 2422, 4755,1C 2391, IC 2602 and IC 4665 for rotation effects. The results
are found to be consistent with the theoretical predictions.
The observed slopes of the rotation effects were used to determine the zero rotation main sequence values of the intermediate
band photometric indices for selected clusters. We also corrected the observed indices for each star in each cluster using
the theoretical predictions of Collins and Sonneborn and derived the ZRMS values for each cluster. The agreement between the
two determinations is found to be good. The various ZRMS curves were utilised to derive the ZRZAMS values. A preliminary calibration
of the absolute visual magnitudes as a function of α valid for ZRZAMS has also been derived. The ZRMS values of the intermediate
band photometric indices for different clusters and the ZRZAMS values are listed as a function of α.
on leave from Assumption College, Changanacherry, Kerala. |
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Keywords: | stars rotation stars colours star clusters individual |
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