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Open Access item Absolute properties of the low-mass eclipsing binary CM Draconis

Authors:Morales, Juan Carlos
Ribas, Ignasi
Jordi, Carme
Torres, Guillermo
Gallardo, José
Guinan, Edward F.
Charbonneau, David
Wolf, Marek
Latham, David W.
Anglada, Guillem
Bradstreet, David H.
Everett, Mark E.
O'Donovan, Francis T.
Keywords:Binaries: eclipsing, Binaries: spectroscopic, Stars: late-type, Stars: fundamental parameters, Stars: individual (CM Dra)
Issue Date:1-Feb-2009
Publisher:American Astronomical Society
Institute of Physics Publishing
Citation:The Astrophysical Journal 691(2): 1400-1411 (2009)
Abstract:Spectroscopic and eclipsing binary systems offer the best means for determining accurate physical properties of stars, including their masses and radii. The data available for low-mass stars have yielded firm evidence that stellar structure models predict smaller radii and higher effective temperatures than observed, but the number of systems with detailed analyses is still small. In this paper, we present a complete reanalysis of one of such eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light curves as well as a radial velocity curve are modeled to measure the physical properties of both components. The masses and radii determined for the components of CM Dra are M1 = 0.2310 ± 0.0009 Msun, M2 = 0.2141 ± 0.0010 Msun, R1 = 0.2534 ± 0.0019 Rsun, and R2 = 0.2396 ± 0.0015 Rsun. With relative uncertainties well below the 1% level, these values constitute the most accurate properties to date for fully convective stars. This makes CM Dra a valuable benchmark for testing theoretical models. In comparing our measurements with theory, we confirm the discrepancies previously reported for other low-mass eclipsing binaries. These discrepancies seem likely to be due to the effects of magnetic activity. We find that the orbit of this system is slightly eccentric, and we have made use of eclipse timings spanning three decades to infer the apsidal motion and other related properties.
Description:12 pages, 7 figures.-- ArXiv pre-print available at: http://arxiv.org/abs/0810.1541
Publisher version (URL):http://dx.doi.org/10.1088/0004-637X/691/2/1400
URI:http://hdl.handle.net/10261/10793
ISSN:0004-637X
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