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

Knudstrup, E.; Gandolfi, D.; Nowak, G.; Persson, C. M.; Furlan, E.; Livingston, J.; Matthews, E.; Lundkvist, M. S.; Winther, M. L.; Rorsted, 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.; Kabath, 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.

doi:10.1093/mnras/stac3684

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.