A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113
Bouchy, F.; Deleuil, M.; Helled, R.; Winn, J. N.; Adibekyan, V.; Hoyer, S.; Sousa, S. G.; Barrado, D.; Barros, S. C. C.; Collins, K. A.; Conti, D. M.; Demangeon, O. D. S.; Jenkins, J. M.; Osborn, H. P.; Santos, N. C.; Seager, S.; Udry, S.; Lillo-Box, J.; Figueira, P.; Wheatley, P. J.; Díaz, R. F.; Latham, D. W.; Ricker, G.; Vanderspek, R.; Anderson, D. R.; Hellier, C.; Stassun, K. G.; Jensen, E. L. N.; West, R.; Delgado-Mena, E.; Briceño, C.; Daylan, T.; Howell, S. B.; Mann, A. W.; Caldwell, D. A.; Smith, J. C.; Nielsen, L. D.; Armstrong, D. J.; Otegi, J. F.; Bayliss, D.; Brown, D. J. A.; Bryant, E. M.; Burke, C.; Dorn, C.; Rackham, B. V.; King, G. W.; Ziegler, C.; Dragomir, D.; Law, N.; Louie, D. R.; Osborn, A.; Pollacco, D. L.; Rodriguez, D. R.; Scott, N. J.; Strøm, P.; Villaseñor, J.
Switzerland, United States, United Kingdom, Portugal, Spain, Canada, Chile, Argentina, France
Abstract
We report the discovery of HD 110113 b (TESS object of interest-755.01), a transiting mini-Neptune exoplanet on a 2.5-d orbit around the solar-analogue HD 110113 (Teff = 5730 K). Using TESS photometry and High Accuracy Radial velocity Planet Searcher (HARPS) radial velocities gathered by the NCORES program, we find that HD 110113 b has a radius of 2.05 ± 0.12 R⊕ and a mass of 4.55 ± 0.62 M⊕. The resulting density of $2.90^{+0.75}_{-0.59}$ g cm-3 is significantly lower than would be expected from a pure-rock world; therefore HD 110113 b must be a mini-Neptune with a significant volatile atmosphere. The high incident flux places it within the so-called radius valley; however, HD 110113 b was able to hold on to a substantial (0.1-1 per cent) H-He atmosphere over its ~4 Gyr lifetime. Through a novel simultaneous Gaussian process fit to multiple activity indicators, we were also able to fit for the strong stellar rotation signal with period 20.8 ± 1.2 d from the RVs and confirm an additional non-transiting planet, HD 110113 c, which has a mass of 10.5 ± 1.2 M⊕ and a period of $6.744^{+0.008}_{-0.009}$ d.