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Astron. Astrophys. 356, L37-L40 (2000)

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5. Conclusion

The detailed study of light curve shapes of Cepheids of different metallicities is essential for a progress of our knowledge of the stellar interiors; in fact, the difficulties of nonlinear models (including also the treatment of turbulent convection) to reproduce satisfactorily the observations point towards the need of further improvement of input physics.

Some Cepheids in IC 1613 with P near 10 d show low order Fourier parameters which are apparently compatible with theoretical model predictions for [FORMULA]. If this was confirmed by further observations, the conclusion would be that the models are just too sensitive to metallicity differences, and therefore simple parameter adjustements would probably suffice to improve the situation. However, a comparison with SMC Cepheids suggests that the partial compatibility is only apparent, and it is due just to the poor number of Cepheids in IC 1613. We stress the importance of observing other very metal poor irregular galaxies, such as NGC 6822, in order to increase the number of stars and verify the sensitivity of the 10 d resonance effects to the metallicity. If also the metal poorest galaxies did not substantiate such a sensitivity (as already done by LMC and SMC), we would remain with an even more serious problem than it is presently deemed.

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© European Southern Observatory (ESO) 2000

Online publication: April 10, 2000