EDP Sciences
Free access
Volume 428, Number 1, December II 2004
Page(s) 209 - 214
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20041266

A&A 428, 209-214 (2004)
DOI: 10.1051/0004-6361:20041266

Synthetic photometry for non-radial pulsations in subdwarf B stars

B. Ramachandran1, C. S. Jeffery1 and R. H. D. Townsend2, 3

1  Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK
    e-mail: brc@arm.ac.uk
2  Bartol Research Institute, University of Delaware, Newark, DE 19716, USA
3  Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK

(Received 10 May 2004 / Accepted 12 August 2004 )

We describe a method for computing theoretical photometric amplitude ratios for a number of modes of nonradially pulsating subdwarf B stars in both SDSS and UBVR systems. In order to avoid costly solutions of the non-adiabatic non-radial pulsation equations, we have adopted the adiabatic approximation. We argue that this is a valid approach, at least for the V361 Hya stars, because observations show that the temperature perturbations dominate the radius perturbations in the flux variation. We find that for V361 Hya stars, low-degree ( $\ell=0,1,2$) modes may be difficult to distinguish using optical photometry. However, the high degree modes ( $\ell= 3,4$) are relatively well separated and may be distinguished more easily. We have also computed the amplitude ratios for a number of modes in PG 1716+426 stars. For these stars, the amplitude ratios for low degree modes ( $\ell=0,1$) are well resolved. For oscillations with periods ~ 40 min, higher-degree modes ( $\ell=2{-}4$) may also be identified easily from their amplitude ratios. However for longer period oscillations, the  $\ell=3$ and the  $\ell=2,4$ modes approach the $\ell=0$ and  $\ell=1$ modes respectively.

Key words: stars: subdwarfs -- stars: atmospheres -- stars: variables: general

SIMBAD Objects

© ESO 2004