EDP Sciences
Free access
Volume 371, Number 1, May III 2001
Page(s) 233 - 239
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20010375

A&A 371, 233-239 (2001)
DOI: 10.1051/0004-6361:20010375

Bi-modal pulsation of the $\delta$ Scuti star V1821 Cygni

A.-Y. Zhou, Z.-L. Liu and B.-T. Du

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China

(Received 8 January 2001 / Accepted 15 March 2001)

The results of Johnson V time-series CCD photometry of the $\delta$ Scuti star V1821 Cygni are presented. Our data set consists of 2431 differential magnitudes and spans the period of July 1999 to September 2000. We detect two best-fit pulsation frequencies representing the light variations of the variable. V1821 Cyg is most likely pulsating in a mixture of radial and nonradial modes. The $uvby\beta$ data in the existing catalogues have been used to derive the main physical parameters for the variable. We obtain: $T_{\rm eff}=7490\pm 200$ K, $M_{V}=1\fm02\pm0.2$, $\log g=3.75\pm 0.1$ dex, $M=2.3\pm0.2 M_{\odot}$, $R=3.3\pm0.3 R_{\odot}$, $\bar{\rho}=0.06\pm0.01 \bar{\rho}_{\odot}$, ${\rm age}=1.0\pm 0.1$ Gyr and a distance modulus of ~$9\fm$12. V1821 Cyg is suggested to be a Population I $\delta$ Scuti star with metal-enriched abundances ( ${\rm [M/H]}=0.366$) evolving on its late main sequence stage on the basis of the colour indices and derived properties.

Key words: stars: $\delta$ Scuti stars -- stars: oscillations -- stars: individual: V1821 Cygni

Offprint request: A.-Y. Zhou, aiying@bao.ac.cn

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