TOI-1268b: the youngest, hot, Saturn-mass transiting exoplanet

• Main Authors: Šubjak, J, Endl, M, Chaturvedi, P, Karjalainen, R, Cochran, W. D, Esposito, M, Gandolfi, D, Lam, K. W. F, Stassun, K, Žák, J, Lodieu, N, Boffin, H. M. J, MacQueen, P. J, Hatzes, A, Guenther, E. W, Georgieva, I, Grziwa, S, Schmerling, H, Skarka, M, Blažek, M, Karjalainen, M, Špoková, M, Isaacson, H, Howard, A. W, Burke, C. J, Van Eylen, V, Falk, B, Fridlund, M, Goffo, E, Jenkins, J. M, Korth, J, Lissauer, J. J, Livingston, J. H, Luque, R, Muresan, A, Osborn, H. P, Pallé, E, Persson, C. M, Redfield, S, Ricker, G. R, Seager, S, Serrano, L. M, Smith, A. M. S, Kabáth, P
• Format: Journal Article
• Language: English
• Published: 23-02-2022
• Subjects: Physics - Earth and Planetary Astrophysics
• DOI: 10.48550/arxiv.2201.13341

A&A 662, A107 (2022) We report the discovery of TOI-1268b, a transiting Saturn-mass planet from
the TESS space mission. With an age of less than one Gyr, derived from various
age indicators, TOI-1268b is the youngest Saturn-mass planet known to date and
contributes to the small sample of well characterised young planets. It has an
orbital period of $P\,=\,8.1577080\pm0.0000044$ days, and transits an early K
dwarf star with a mass of $M_\star$ = $ 0.96 \pm 0.04$ $M_{\odot}$, a radius of
$R_\star$ = $ 0.92 \pm 0.06$ $R_{\odot}$, an effective temperature of
$T_\mathrm{eff}\,=\,5300\pm100$ K, and a metallicity of $0.36\pm0.06$ dex. By
combining TESS photometry with high-resolution spectra acquired with the Tull
spectrograph at McDonald observatory, and the high-resolution spectrographs at
Tautenburg and Ondrejov observatories, we measured a planetary mass of
$M_\mathrm{p}\,=\,96.4 \pm 8.3\,M_{\oplus}$ and a radius of
$R_\mathrm{p}\,=\,9.1 \pm 0.6\,R_{\oplus}$. TOI-1268 is an ideal system to
study the role of star-planet tidal interactions for non-inflated Saturn-mass
planets. We used system parameters derived in this paper to constrain the
planet tidal quality factor to the range of $10^{4.5-5.3}$. When compared with
the sample of other non-inflated Saturn-mass planets, TOI-1268b is one of the
best candidates for transmission spectroscopy studies.