Hot planets around cool stars - Two short-period mini-Neptunes transiting the late K-dwarf TOI-1260

Summary, in English

We present the discovery and characterization of two sub-Neptunes in close orbits, as well as a tentative outer planet of a similar size, orbiting TOI-1260 - a low metallicity K6 V dwarf star. Photometry from Transiting Exoplanet Survey Satellite(TESS) yields radii of Rb = 2.33 ± 0.10 and Rc = 2.82 ± 0.15 R⊕, and periods of 3.13 and 7.49 d for TOI-1260 b and TOI-1260 c, respectively. We combined the TESS data with a series of ground-based follow-up observations to characterize the planetary system. From HARPS-N high-precision radial velocities we obtain Mb = 8.6- 1.5+ 1.4 and Mc = 11.8- 3.2+ 3.4 M⊕. The star is moderately active with a complex activity pattern, which necessitated the use of Gaussian process regression for both the light-curve detrending and the radial velocity modelling, in the latter case guided by suitable activity indicators. We successfully disentangle the stellar-induced signal from the planetary signals, underlining the importance and usefulness of the Gaussian process approach. We test the system's stability against atmospheric photoevaporation and find that the TOI-1260 planets are classic examples of the structure and composition ambiguity typical for the 2-3 R⊕ range.

• Author: I. Y. Georgieva; C. M. Persson; O. Barragán; G. Nowak; M. Fridlund; D. Locci; E. Palle; R. Luque; I. Carleo; D. Gandolfi; S. R. Kane; J. Korth; K. G. Stassun; J. Livingston; E. C. Matthews; K. A. Collins; S. B. Howell; L. M. Serrano; S. Albrecht; A. Bieryla; C. E. Brasseur; D. Ciardi; W. D. Cochran; K. D. Colon; I. J.M. Crossfield; Sz Csizmadia; H. J. Deeg; M. Esposito; E. Furlan; T. Gan; E. Goffo; E. Gonzales; S. Grziwa; E. W. Guenther; P. Guerra; T. Hirano; J. M. Jenkins; E. L.N. Jensen; P. Kabáth; E. Knudstrup; K. W.F. Lam; D. W. Latham; A. M. Levine; R. A. Matson; S. McDermott; H. L.M. Osborne; M. Paegert; S. N. Quinn; S. Redfield; G. R. Ricker; J. E. Schlieder; N. J. Scott; S. Seager; A. M.S. Smith; P. Tenenbaum; J. D. Twicken; R. Vanderspek; V. Van Eylen; J. N. Winn
• Publishing year: 2021-08-01
• Language: English
• Pages: 4684-4701
• Publication/Series: Monthly Notices of the Royal Astronomical Society
• Volume: 505
• Issue: 4
• Links: http://dx.doi.org/10.1093/mnras/stab1464
• Document type: Journal article
• Publisher: Oxford University Press
• Keywords: planetary systems; planets and satellites: atmospheres; planets and satellites: composition; planets and satellites: individual: TOI-1260b, c; stars: low-mass; techniques: photometric; techniques: radial velocities
• Status: Published
• ISBN/ISSN/Other: ISSN: 0035-8711