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; Teff = $6478^{+94}{-89}$ K), discovered as part of the Next Generation Transit Survey (NGTS). The planet is in a P = 4.51 d orbit with mass $0.74^{+0.13}{-0.12}$MJ, radius $1.595^{+0.047}{-0.045}$RJ, and density $0.226^{+0.040}{-0.038}$ g cm−3; therefore one of the lowest density exoplanets currently known. With a relatively deep $1.0{{\ \rm per\ cent}}$ 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 ($v$ sin i = 15.2 ± 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.