A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

OSBORN, H. P; ARMSTRONG, D.J.; ADIBEKYAN, V.; COLLINS, K.A.; DELGADO-MENA, E.; HOWELL, S.B.; HELLIER, C.; KING, G.W.; LILLO-BOX, J.; NIELSEN, L.D.; OTEGI, J.F.; SANTOS, N.C.; ZIEGLER, C.; ANDERSON, D.R.; BRICENO, C.; BURKE, C; BAYLISS, D; BARRADO, D; BRYANT, E. M; BROWN, D. J. A; BARROS, S. C. C; BOUCHY, F; CALDWELL, D. A; CONTI, D. M; DIAZ, R. F; DRAGOMIR, D; DELEUIL, M; DEMANGEON, O. D. S; DORN, C; DAYLAN, T; FIGUEIRA, P; HELLED, R; HOYER, S; JENKINS, J. M; JENSEN, E. L. N; LATHAM, D. W; LAW, N; LOUIE, D. R; MANN, A. W; OSBORN, A; POLLACCO, D. L; RODRIGUEZ, D. R; RACKHAM, B. V; RICKER, G; SCOTT, N. J; SOUSA, S. G; SEAGER, S; STASSUN, K. G; SMITH, J. C; STRM, P; UDRY, S; VILLASENOR, J; VANDERSPEK, R; WEST, R; WHEATLEY, P. J; WINN, J. N

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2021 vol. 502 p. 4842 - 4857

0035-8711

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.