We report the discovery of three low-mass double-lined eclipsing binaries in the pre-main sequence Upper Scorpius association , revealed by K 2 photometric monitoring of the region over \sim 78 days .
The orbital periods of all three systems are < 5 days .
We use the K 2 photometry plus multiple Keck/HIRES radial velocities and spectroscopic flux ratios to determine fundamental stellar parameters for both the primary and secondary components of each system , along with the orbital parameters .
We present tentative evidence that EPIC 203868608 is a hierarchical triple system comprised of an eclipsing pair of \sim 25 M _ { \mathrm { Jup } } brown dwarfs with a wide M-type companion .
If confirmed , it would constitute only the second double-lined eclipsing brown dwarf binary system discovered to date .
The double-lined system EPIC 203710387 is composed of nearly identical M4.5-M5 stars with fundamentally determined masses and radii measured to better than 3 % precision ( M _ { 1 } = 0.1183 \pm 0.0028 M _ { \odot } , M _ { 2 } = 0.1076 \pm 0.0031 M _ { \odot } and R _ { 1 } = 0.417 \pm 0.010 R _ { \odot } , R _ { 2 } = 0.450 \pm 0.012 R _ { \odot } ) from combination of the light curve and radial velocity time series .
These stars have the lowest masses of any stellar mass double-lined eclipsing binary to date .
Comparing our derived stellar parameters with evolutionary models suggest an age of \sim 10-11 Myr for this system , in contrast to the canonical age of 3-5 Myr for the association .
Finally , EPIC 203476597 is a compact single-lined system with a G8-K0 primary and a likely mid-K secondary whose line are revealed in spectral ratios .
Continued measurement of radial velocities and spectroscopic flux ratios will better constrain fundamental parameters and should elevate the objects to benchmark status .
We also present revised parameters for the double-lined eclipsing binary UScoCTIO 5 ( M _ { 1 } = 0.3336 \pm 0.0022 M _ { \odot } , M _ { 2 } = 0.3200 \pm 0.0022 M _ { \odot } and R _ { 1 } = 0.862 \pm 0.012 , R _ { 2 } = 0.852 \pm 0.013 R _ { \odot } ) , which are suggestive of a system age younger than previously reported .
We discuss the implications of our results on these \sim 0.1-1.5 M _ { \odot } stars for pre-main-sequence evolutionary models .