James R. A. Davenport, Andrew C. Becker, Andrew A. West, John J. Bochanski, Suzanne L. Hawley, Jon Holtzman, Heather C. Gunning, Eric J. Hilton, Ferah D. Munshi, Meagan Albright
We present follow-up observations and analysis of the recently discovered short period low-mass eclipsing binary, SDSS J001641-000925. With an orbital period of 0.19856 days, this system belongs to a very rare class of contact eclipsing binaries, and has one of the shortest known periods for an M dwarf binary system. Medium-resolution spectroscopy and multi-band photometry for the system are presented. Markov chain Monte Carlo modeling of the light curves and radial velocities yield estimated masses for the stars of M_1 =0.54+/-0.07M_sun and M_2 =0.34+/-0.04M_sun, and radii of R_1 =0.68+/-0.03 R_sun and R_2 = 0.58 +/- 0.03 R_sun respectively. An overcontact scenario is strongly preferred by the binary model. Both stellar components are found to exhibit magnetic activity through H_alpha emission. Using both sparsely sampled survey photometry and dedicated monitoring, the orbital period is found to decrease by dP/dt ~ 8 s yr^{-1}. This is one of the largest amplitude period decays observed for a W UMa type binary, indicating that the system is in contact and losing angular momentum. SDSS J001641-000925 is thus the first verified contact M dwarf binary system.
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http://arxiv.org/abs/1206.6056
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