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Astronomy & Astrophysics manuscript no. January 29, 2002 (DOI: will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no. January 29, 2002
(DOI: will be inserted by hand later)
Non-linear radial pulsation models for the early-type helium stars
V652 Her and BX Cir
P. Monta~nŽes RodrŽiguez and C. S. Jeffery
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
Received 18 September 2001 / Accepted 2 January 2002
Abstract. We report new non-linear pulsation models of the helium stars V652 Her and BX Cir. Linear theory has
previously shown their pulsations to be due to iron-group bump instability. Recent high-resolution spectroscopic
observations have provided high-precision measurements of their radial velocity curves and of their radii. Their
masses remain less well determined. A hydrodynamic code including recent OPAL opacity data has been used to
construct the models. These are compared with the observational data. In particular, we attempt to reproduce
accurately the observed radial velocity and luminosity curves. The results impose additional constraints on those
stellar dimensions, including mass, which remain poorly determined by observation. Final results show a model
for V652 Her which reproduce the observed velocity and luminosity curves with 0.7 M and 23 400 K. For BX Cir,
the mass must lie between 0.50 and 0.38 M if the temperature is in the range 22 400­24 000 K. However, the
luminosity of the models is smaller than that measured directly by a factor of two.
Key words. stars: helium ­ stars: individual V652 Her ­ stars: individual BX Cir ­ stars: oscillations ­
stars: early-type
1. Introduction


Source: Armagh Observatory
Jeffery, Simon - Armagh Observatory


Collections: Physics