Astronomy and Astrophysics, volume 291, 795-804 (1994/11-3)
AG Persei: absolute dimensions and membership of Perseus OB2.
GIMENEZ A. and CLAUSEN J.V.
Abstract (from CDS):
Accurate physical parameters for the B-type eclipsing binary AG Per (HD 25833; B4 V, V=6.7, P=2.03d) have been determined from a complete re-analysis of available light curves and recent spectroscopic elements (Popper & Hill 1991). The components have masses of 5.36±0.16 and 4.90±0.13M☉ and radii of 2.99±0.07 and 2.60±0.07R☉, respectively, and they are among the least evolved B stars with well-determined dimensions. Effective temperatures of 18200±800K and 17400±800K are derived. The orbit is slightly eccentric (e=0.0710±0.0010) and shows apsidal motion with a well-established period of U=75.6±0.6yr. Comparison with stellar evolution models based on the latest opacity library by Rogers & Iglesias (1992) and including a moderate amount of convective overshooting (Claret & Gimenez 1992) shows AG Per to be young; an age of about 4-6x107yr is derived from the scale independent masses and radii. AG Per is too little evolved to provide any constraints on the amount of convective overshooting. We find some indication that AG Per, like other recently studied early-type binaries, is metal-deficient compared to the (much older) Sun. We recommend a detailed spectroscopic determination of the metal abundance for AG Per. The mean density concentration coefficient determined from the apsidal motion parameters, logk2=-2.14±0.04, agrees well with that computed for the models, provided a relativistic correction based on the general relativity theory is included. In its present formulation and calibration the alternative non-symmetric gravitational theory proposed by Moffat (1989) is not supported. AG Per is generally accepted as a member of Per OB2. We find a distance of 355±30pc for the binary, compared to 330-420pc given by various authors for the association. New stellar models and calibrations indicate a photometric age of about 1-1.5x107yr for Per OB2, larger than previously obtained but still well below that of AG Per (4-6x107yr). This weakens - at least for the moment - the status of AG Per as a member. New observations of (potential) Per OB2 members, including fainter stars, are clearly needed.
binaries: eclipsing - stars: fundamental parameters - stars: evolution - stars: individual: AG Per - open clusters and associations: individual: Ass Per OB 2