ABSOLUTE DIMENSIONS OF THE G7+K7 ECLIPSING BINARY STAR IM VIRGINIS: DISCREPANCIES WITH STELLAR EVOLUTION MODELS
- Institut d'Estudis Espacials de Catalunya (IEEC), Edif. Nexus, C/Gran Capita, 2-4, 08034 Barcelona (Spain)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Physics, Gettysburg College, 300 North Washington Street, Gettysburg, PA 17325 (United States)
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 M {sub 1} = 0.981 +- 0.012 M {sub sun}, M {sub 2} = 0.6644 +- 0.0048 M {sub sun}, R {sub 1} = 1.061 +- 0.016 R {sub sun}, and R {sub 2} = 0.681 +- 0.013 R {sub sun} 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] approx-0.3 that is consistent with other indications, but requires confirmation.
- OSTI ID:
- 21389288
- Journal Information:
- Astrophysical Journal, Vol. 707, Issue 1; Other Information: DOI: 10.1088/0004-637X/707/1/671; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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