We present the discovery of KELT J072709+072007 ( HD 58730 ) , a very low mass ratio ( q \equiv M _ { 2 } / M _ { 1 } \approx 0.08 ) eclipsing binary ( EB ) identified by the Kilodegree Extremely Little Telescope ( KELT ) survey .
We present the discovery light curve and perform a global analysis of four high-precision ground-based light curves , the Transiting Exoplanets Survey Satellite ( TESS ) light curve , radial velocity ( RV ) measurements , Doppler Tomography ( DT ) measurements , and the broad-band spectral energy distribution ( SED ) .
Results from the global analysis are consistent with a fully convective ( M _ { 2 } = 0.253 ^ { +0.021 } _ { -0.017 } M \textsubscript { $ \odot$ } ) M star transiting a late-B primary ( M _ { 1 } = 3.348 ^ { +0.057 } _ { -0.082 } M \textsubscript { $ \odot$ } ; T _ { eff, 1 } = 1200 % 0 ^ { +580 } _ { -530 } { K } ) .
We infer that the system is younger than 272 Myr ( 3 \sigma ) , and the M star mass and radius are consistent with values from a pre-main sequence isochrone of comparable age .
We separately and analytically fit for the variability in the out-of-eclipse TESS phase curve , finding good agreement between these results and those from the global analysis .
Such systems are valuable for testing theories of binary star formation and understanding how the environment of a star in a close-but-detached binary affects its physical properties .
In particular , we examine how a star ’ s properties in such a binary might differ from the properties it would have in isolation .