NGTS-6b: an ultrashort period hot-Jupiter orbiting an old K dwarf

We report the discovery of a new ultrashort period hot Jupiter from the Next Generation Transit Survey. NGTS-6b orbits its star with a period of 21.17 h, and has a mass and radius of 1.330^{+0.024}_{-0.028}M_J and 1.271^{+0.197}_{-0.188}R_J, respectively, returning a planetary bulk density of 0.711^{+0.214}_{-0.136} g cm^-3. Conforming to the currently known small population of ultrashort period hot Jupiters, the planet appears to orbit a metal-rich star ([Fe/H] = +0.11 ± 0.09 dex). Photoevaporation models suggest the planet should have lost 5 per cent of its gaseous atmosphere over the course of the 9.6 Gyr of evolution of the system. NGTS-6b adds to the small, but growing list of ultrashort period gas giant planets, and will help us to understand the dominant formation and evolutionary mechanisms that govern this population.