TOI-908: a planet at the edge of the Neptune desert transiting a G-type star

We present the discovery of an exoplanet transiting TOI-908 (TIC-350153977) using data from TESS sectors 1, 12, 13, 27, 28, and 39. TOI-908 is a T = 10.7 mag G-dwarf (T-eff = 5626 +/- 61 K) solar-like star with a mass of 0.950 +/- 0.010 M (circle dot) and a radius of 1.028 +/- 0.030 R-circle dot. The planet, TOI-908 b, is a 3.18 +/- 0.16 R-circle plus planet in a 3.18 d orbit. Radial velocity measurements from HARPS reveal TOI-908 b has a mass of approximately 16.1 +/- 4.1 M-circle plus, resulting in a bulk planetary density of 2.7(-0.4)(+0.2) g cm(-3). TOI-908 b lies in a sparsely populated region of parameter space known as the Neptune desert. The planet likely began its life as a sub-Saturn planet before it experienced significant photoevaporation due to X-rays and extreme ultraviolet radiation from its host star, and is likely to continue evaporating, losing a significant fraction of its residual envelope mass.

Automated summary

We present the discovery of exoplanet TOI-908 b orbiting the G-dwarf star TOI-908 using TESS data. TOI-908 b is a 3.18 R-circle plus planet with a period of 3.18 days. Radial velocity measurements reveal a mass of approximately 16.1 M-circle plus and a bulk density of 2.7(-0.4)(+0.2) g cm(-3). The planet lies in the Neptune desert and likely underwent significant photoevaporation from its host star.