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

August 2021 • 2021MNRAS.505.4684G

Authors • Georgieva, I. Y. • Persson, C. M. • Barragán, O. • Nowak, G. • Fridlund, M. • Locci, D. • Palle, E. • Luque, R. • Carleo, I. • Gandolfi, D. • Kane, S. R. • Korth, J. • Stassun, K. G. • Livingston, J. • Matthews, E. C. • Collins, K. A. • Howell, S. B. • Serrano, L. M. • Albrecht, S. • Bieryla, A. • Brasseur, C. E. • Ciardi, D. • Cochran, W. D. • Colon, K. D. • Crossfield, I. J. M. • Csizmadia, Sz • Deeg, H. J. • Esposito, M. • Furlan, E. • Gan, T. • Goffo, E. • Gonzales, E. • Grziwa, S. • Guenther, E. W. • Guerra, P. • Hirano, T. • Jenkins, J. M. • Jensen, E. L. N. • Kabáth, P. • Knudstrup, E. • Lam, K. W. F. • Latham, D. W. • Levine, A. M. • Matson, R. A. • McDermott, S. • Osborne, H. L. M. • Paegert, M. • Quinn, S. N. • Redfield, S. • Ricker, G. R. • Schlieder, J. E. • Scott, N. J. • Seager, S. • Smith, A. M. S. • Tenenbaum, P. • Twicken, J. D. • Vanderspek, R. • Van Eylen, V. • Winn, J. N.

Abstract • 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 R_b = 2.33 ± 0.10 and R_c = 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 M_b = $8.6 _{ - 1.5 } ^ { + 1.4 }$ and M_c = $11.8 _{ - 3.2 } ^ { + 3.4 }$ 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.

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• ELECTR https://doi.org/10.1093%2Fmnras%2Fstab1464