* Astronomy

Title: Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?
Authors: David T. F. Weldrake (1), Daniel D. R. Bayliss (2), Penny D. Sackett (2), Brandon W. Tingley (3), Michael Gillon (4,5), Johny Setiawan (1) ((1) MPIA, Heidelberg, (2) RSAA, Mount Stromlo Observatory, (3) Institute d'Astronomy et Astrophysique, ULB, (4) Geneva Observatory, (5) Institut d'Astrophysique et de Geophysique, Universite De Liege.)

We present a prime case for a transiting Hot Jupiter planet identified during a single-field transit survey towards the Lupus region of the Galactic plane. The object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d. Spectroscopy and stellar colours indicate a host star with effective temperature 5000 ±150 K, with a stellar mass and radius of 0.87 ±0.04 Msun and 0.82 ±0.05 Rsun, respectively. Limb-darkened transit fitting yields a companion radius of 0.89 ±0.07 Rjup and an orbital inclination of 88.3{+1.3}{-0.8} deg. Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 ±25 m/s sinusoidal variation in phase with the transit ephemeris. The resulting mass is 0.81 ±0.18 Mjup and density 1.4 ±0.4 g/cm³. Y-band PANIC image deconvolution reveal a V>=21 red neighbour 0.4'' away which, although highly unlikely, we cannot conclusively rule out as a blended binary with current data. However, no in-phase bisector variations are observed and 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. If confirmed, Lupus-TR-3b will become the faintest ground-based detection to date, and one of the lowest mass Hot Jupiters known.

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