Asteroseismology of the ZZ Ceti star HS 0507+0434B

Fu, J. -N. and Dolez, N. and Vauclair, G. and Fox, Machado L. and Kim, S. -L. and Li, C. and Chen, L. and Alvarez, M. and Su, J. and Charpinet, S. and Chevreton, M. and Michel, R. and Yang, X. H. and Li, Y. and Zhang, Y. P. and Molnár, László and Plachy, Emese (2013) Asteroseismology of the ZZ Ceti star HS 0507+0434B. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 429 (2). pp. 1585-1595. ISSN 0035-8711

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Abstract

The pulsating DA white dwarfs (ZZ Ceti stars) are g-mode non-radial pulsators. Asteroseis- mology provides strong constraints on their global parameters and internal structure. Since all the DA white dwarfs falling in the ZZ Ceti instability strip do pulsate, the internal structure derived from asteroseismology brings knowledge for the DA white dwarfs as a whole group. HS 0507+0434B is one of the ZZ Ceti stars which lies approximately in the middle of the instability strip for which we have undertaken a detailed asteroseismological study. We car- ried out multisite observation campaigns in 2007 and from December 2009 to January 2010. In total, 206 hours of photometric time-series have been collected. They have been analysed by means of Fourier analysis and simultaneous multi-frequency sine-wave fitting. In total, 39 frequency values are resolved including 6 triplets and a number of linear combinations. We identify the triplets as ℓ=1 g-modes split by rotation. We derived the period spacing, the ro- tational splitting and the rotation rate. From the comparison of the observed periods with the theoretical periods of a series of models we estimate the fundamental parameters of the star: its total mass M∗/M⊙ = 0.675, its luminosity L/L⊙=3.5×10−3, and its hydrogen mass fraction MH /M∗= 10−8.5.

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