Astrophys. J., 707, 671-685 (2009/December-2)
Absolute dimensions of the G7+K7 eclipsing binary star IM Virginis: discrepancies with stellar evolution models.
MORALES J.C., TORRES G., MARSCHALL L.A. and BREHM W.
Abstract (from CDS):
We report extensive spectroscopic and differential photometric BVRI observations of the active, detached, 1.309-day double-lined eclipsing binary IM Vir, composed of a G7-type primary and a K7 secondary. With these observations, we derive accurate absolute masses and radii of M1= 0.981±0.012 M☉, M2= 0.6644±0.0048 M☉, R1= 1.061±0.016 R☉, and R 2= 0.681±0.013 R☉ for the primary and secondary, with relative errors under 2%. The effective temperatures are 5570±100 K and 4250±130 K, respectively. The significant difference in mass makes this a favorable case for comparison with stellar evolution theory. We find that both stars are larger than the models predict, by 3.7% for the primary and 7.5% for the secondary, as well as cooler than expected, by 100 K and 150 K, respectively. These discrepancies are in line with previously reported differences in low-mass stars, and are believed to be caused by chromospheric activity, which is not accounted for in current models. The effect is not confined to low-mass stars: the rapidly rotating primary of IM Vir joins the growing list of objects of near-solar mass (but still with convective envelopes) that show similar anomalies. The comparison with the models suggests an age of 2.4 Gyr for the system, and a metallicity of [Fe/H] ~-0.3 that is consistent with other indications, but requires confirmation.
binaries: eclipsing - binaries: spectroscopic - stars: fundamental parameters - stars: individual: IM Vir - stars: late-type
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<Available at CDS (J/ApJ/707/671): table1.dat table3.dat table4.dat table5.dat table6.dat>
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