NGTS-2b: An inflated hot-Jupiter transiting a bright F-dwarf

Abstract

We report the discovery of NGTS-2b, an inflated hot-Jupiter transiting a bright F5V star (2MASS J14202949-3112074; $T_{\mathrm{eff}}$=$6478_{-89}^{+94}$ K), discovered as part of the Next Generation Transit Survey (NGTS). The planet is in a P=4.51 day orbit with mass $0.74_{-0.12}^{+0.13}$ M${}_J$, radius $1.595_{-0.045}^{+0.047}$ R${}_J$ and density $0.226_{-0.038}^{+0.040}$ g cm${}^{-3}$; therefore one of the lowest density exoplanets currently known. With a relatively deep 1.0% transit around a bright V=10.96 host star, NGTS-2b is a prime target for probing giant planet composition via atmospheric transmission spectroscopy. The rapid rotation ($vsin$i=$15.2\pm 0.8$ km s${}^{-1}$) also makes this system an excellent candidate for Rossiter-McLaughlin follow-up observations, to measure the sky-projected stellar obliquity. NGTS-2b was confirmed without the need for follow-up photometry, due to the high precision of the NGTS photometry.

12 pages, 8 figures, accepted for publication in MNRAS