The Prospects for Finding Brown Dwarfs in Eclipsing Binary Systems and Measuring Brown Dwarf Properties

We present the results of a simulation to investigate the prospects ofmeasuring mass, age, radius, metallicity and luminosity data for brown dwarfsin fully eclipsing binary systems around late K and early M dwarfs identifiedby ultra-wide-field transit surveys. These surveys will monitor approximately amillion K and M dwarfs at a level sufficient to detect transits of lowluminosity companions. We look at the current observational evidence for suchsystems, and suggest that about 1% of late K and early-mid M dwarfs could havea very close BD companion. With this assumption, and using the SuperWASPtransit survey as an example, our simulation predicts that 400 brown dwarfs infully eclipsing binary systems could be discovered. All of these eclipsingbinaries could yield accurate brown dwarf mass and radius measurements. Byinferring the brown dwarf effective temperature distribution, assuming auniform age spread and an alpha=0.5 companion brown dwarf mass function, thesimulation estimates that brown dwarf brightness could also be measurable (atthe 10% level) for about 60 of these binary systems from the secondary eclipse.Irradiation of the brown dwarfs will be below the 10% level for about 70% ofthese systems, meaning that the measured brown dwarf brightnesses shouldgenerally be the same as those of free-floating counterparts. The predicted agedistribution of the primaries is dominated by young systems, and about 20binaries could be younger than 1Gyr. We suggest that many of these young binarysystems will be members of ``kinematic moving groups'', allowing their ages tobe accurately constrained.Comment: 55 pages, 9 figures, to be published in PAS