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First overtone pulsators among Cepheids

Published online by Cambridge University Press:  15 February 2018

L. Mantegazza  and
E. Poretti
L. Mantegazza
Affiliation:
Università degli Studi, Pavia, Italy
E. Poretti
Affiliation:
Osservatorio Astronomico di Brera, Merate, Italy

Extract

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The Fourier decomposition has been successfully applied to several classes of pulsating variables. Antonello and Poretti (1986) and Antonello et al. (1990a) applied it to the Cepheids with P < 8 d. The latter authors redefined the s – Cepheids a Population I Cepheids that do not follow the Hertzsprung progression, but have progression of their own. The same authors proposed a new denomination (Antonell et al., 1990b): C-a stars to indicate the Classical Cepheids and C-b stars to indicate the redefined s–Cepheids.

The new photometric data obtained at La Silla and Merate Observatories (Mantegazza and Poretti, 1992) increase the evidence of a separation of Cepheids into two well defined subclasses on the basis of the Fourier parameters of their light curves.

In the ϕ21 – P plane, the s– and Classical Cepheids are characterized by two sequences well separated for P<5.5 d.

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 370
Copyright
Copyright © Cambridge University Press 1993

References

Antonello, E. and Poretti, E., 1986, Astron. Astrophys. 169, 149.Google Scholar
Antonello, E., Poretti, E., Reduzzi, L., 1990a, Astron. Astrophys. 236, 138.Google Scholar
Antonello, E., Poretti, E., Reduzzi, L., 1990b, in: Confrontation between Stellar Pulsatio and Evolution, Astr. Soc. of Pacific Conf. Series 11, p 209.Google Scholar
Mantegazza, L., Poretti, E., 1992, Astron. Astrophys., in press.Google Scholar