Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?

Abstract

We present a strong case for a transiting hot Jupiter planet identified during a single-field transit survey toward the Lupus Galactic plane. The object, Lupus-TR-3b, transits a Vp17.4 K1 V host star every 3.91405 days. Spectroscopy and stellar colors indicate a host star with effective temperature 5000150 K, with a stellar mass and radius of 0.870.04M and 0.820.05 R , respectively. Limb-darkened transit fitting yields a companion radius of 0.890.07 R and an orbital inclination of 88.30.8 ,, surements reveal a 2.4 j K p 114  25 m s1 J J  deg. Magellan 6.5 m MIKE radial velocity mea- 1.3 resulting mass is 0.81  0.18 M and density 1.4  0.4gcm3 sinusoidal variation in phase with the transit ephemeris. The . Y-band PANIC image deconvolution reveals a V ≥ 21 red neighbor 0.4 away which, although highly unlikely, we cannot conclusively rule out as a blended  binary with current data. However, blend simulations show that only the most unusual binary system can reproduce our observations. This object is very likely a planet, detected from a highly efficient observational strategy. Lupus-TR-3b constitutes the faintest ground-based detection to date, and one of the lowest mass hot Jupiters known.