Skip to main content

Research Repository

Advanced Search

Absolute dimensions of detached eclipsing binaries – III. The metallic-lined system YZ Cassiopeiae

Pavlovski, K.; Southworth, J.; Kolbas, V.; Smalley, B.

Authors

K. Pavlovski

V. Kolbas



Abstract

The bright binary system YZ Cassiopeiae is a remarkable laboratory for studying the Am phenomenon. It consists of a metallic-lined A2 star and an F2 dwarf on a circular orbit, which undergo total and annular eclipses. We present an analysis of 15 published light curves and 42 new high-quality échelle spectra, resulting in measurements of the masses, radii, effective temperatures and photospheric chemical abundances of the two stars. The masses and radii are measured to 0.5 per cent precision: MA = 2.263 ± 0.012 M⊙, MB = 1.325 ± 0.007 M⊙, RA = 2.525 ± 0.011 R⊙ and RB = 1.331 ± 0.006 R⊙. We determine the abundance of 20 elements for the primary star, of which all except scandium are supersolar by up to 1 dex. The temperature of this star (9520 ± 120 K) makes it one of the hottest Am stars. We also measure the abundances of 25 elements for its companion (Teff = 6880 ± 240 K), finding all to be solar or slightly above solar. The photospheric abundances of the secondary star should be representative of the bulk composition of both stars. Theoretical stellar evolutionary models are unable to match these properties: the masses, radii and temperatures imply a half-solar chemical composition (Z = 0.009 ± 0.003) and an age of 490–550 Myr. YZ Cas therefore presents a challenge to stellar evolutionary theory.

Citation

Pavlovski, K., Southworth, J., Kolbas, V., & Smalley, B. (2014). Absolute dimensions of detached eclipsing binaries – III. The metallic-lined system YZ Cassiopeiae. Monthly Notices of the Royal Astronomical Society, 438(1), 590-603. https://doi.org/10.1093/mnras/stt2229

Journal Article Type Article
Acceptance Date Nov 14, 2013
Online Publication Date Dec 10, 2013
Publication Date Feb 11, 2014
Deposit Date Jun 14, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 438
Issue 1
Pages 590-603
DOI https://doi.org/10.1093/mnras/stt2229
Keywords Space and Planetary Science; Astronomy and Astrophysics; stars: abundances, binaries: eclipsing, binaries: spectroscopic, stars: chemically peculiar, stars: fundamental parameters, stars: individual: YZ Cas