GJ 3236: A NEW BRIGHT, VERY LOW MASS ECLIPSING BINARY SYSTEM DISCOVERED BY THE MEARTH OBSERVATORY

We report the detection of eclipses in GJ 3236, a bright (I = 11.6), very low mass binary system with an orbital period of 0.77 days. Analysis of light and radial velocity curves of the system yielded component masses of 0.38 {+-} 0.02 M{sub sun} and 0.28 {+-} 0.02 M{sub sun}. The central values for...

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Bibliographic Details
Published in:	The Astrophysical journal 2009-08, Vol.701 (2)
Main Authors:	Irwin, Jonathan, Charbonneau, David, Berta, Zachory K., Quinn, Samuel N., Latham, David W., Torres, Guillermo, Blake, Cullen H., Burke, Christopher J., Esquerdo, Gilbert A., Fueresz, Gabor, Mink, Douglas J., Nutzman, Philip, Szentgyorgyi, Andrew H., Calkins, Michael L., Falco, Emilio E., Bloom, Joshua S., Starr, Dan L.
Format:	Article
Language:	eng
Subjects:	ACTIVITY LEVELS ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ECLIPSE MASS PHOTOMETRY RADIAL VELOCITY STARS
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Summary:	We report the detection of eclipses in GJ 3236, a bright (I = 11.6), very low mass binary system with an orbital period of 0.77 days. Analysis of light and radial velocity curves of the system yielded component masses of 0.38 {+-} 0.02 M{sub sun} and 0.28 {+-} 0.02 M{sub sun}. The central values for the stellar radii are larger than the theoretical models predict for these masses, in agreement with the results for existing eclipsing binaries, although the present 5% observational uncertainties limit the significance of the larger radii to approximately 1{sigma}. Degeneracies in the light curve models resulting from the unknown configuration of surface spots on the components of GJ 3236 currently dominate the uncertainties in the radii, and could be reduced by obtaining precise, multiband photometry covering the full orbital period. The system appears to be tidally synchronized and shows signs of high activity levels as expected for such a short orbital period, evidenced by strong H{alpha} emission lines in the spectra of both components. These observations probe an important region of mass-radius parameter space around the predicted transition to fully convective stellar interiors, where there are a limited number of precise measurements available in the literature.
ISSN:	0004-637X 1538-4357