Radial velocity confirmation of a hot super-Neptune discovered by TESS with a warm Saturn-mass companion

March 2023 • 2023MNRAS.519.5637K

Authors • Knudstrup, E. • Gandolfi, D. • Nowak, G. • Persson, C. M. • Furlan, E. • Livingston, J. • Matthews, E. • Lundkvist, M. S. • Winther, M. L. • Rørsted, J. L. • Albrecht, S. H. • Goffo, E. • Carleo, I. • Deeg, H. J. • Collins, K. A. • Narita, N. • Isaacson, H. • Redfield, S. • Dai, F. • Hirano, T. • Akana Murphy, J. M. • Beard, C. • Buchhave, L. A. • Cary, S. • Chontos, A. • Crossfield, I. • Cochran, W. D. • Conti, D. • Dalba, P. A. • Esposito, M. • Fajardo-Acosta, S. • Giacalone, S. • Grunblatt, S. K. • Guerra, P. • Hatzes, A. P. • Holcomb, R. • Horta, F. G. • Howard, A. W. • Huber, D. • Jenkins, J. M. • Kabáth, P. • Kane, S. • Korth, J. • Lam, K. W. F. • Lester, K. V. • Matson, R. • McLeod, K. K. • Orell-Miquel, J. • Murgas, F. • Palle, E. • Polanski, A. S. • Ricker, G. • Robertson, P. • Rubenzahl, R. • Schlieder, J. E. • Seager, S. • Smith, A. M. S. • Tenenbaum, P. • Turtelboom, E. • Vanderspek, R. • Weiss, L. • Winn, J.

Abstract • We report the discovery and confirmation of the planetary system TOI-1288. This late G dwarf harbours two planets: TOI-1288 b and TOI-1288 c. We combine TESS space-borne and ground-based transit photometry with HARPS-N and HIRES high-precision Doppler measurements, which we use to constrain the masses of both planets in the system and the radius of planet b. TOI-1288 b has a period of $2.699835^{+0.000004}_{-0.000003}$ d, a radius of 5.24 ± 0.09 R, and a mass of 42 ± 3 M, making this planet a hot transiting super-Neptune situated right in the Neptunian desert. This desert refers to a paucity of Neptune-sized planets on short period orbits. Our 2.4-yr-long Doppler monitoring of TOI-1288 revealed the presence of a Saturn-mass planet on a moderately eccentric orbit ($0.13^{+0.07}_{-0.09}$) with a minimum mass of 84 ± 7 M and a period of $443^{+11}_{-13}$ d. The five sectors worth of TESS data do not cover our expected mid-transit time for TOI-1288 c, and we do not detect a transit for this planet in these sectors.