Planet Hunters TESS III: two transiting planets around the bright G dwarf HD 152843
Aigrain, S.; Stassun, K.; Barragán, O.; Lee, S.; Jenkins, J. M.; Seager, S.; Llama, J.; Ricker, G.; Winn, J.; Zicher, N.; Mortier, A.; Buchhave, L. A.; Tkachenko, A.; Klein, B.; Latham, D.; Caldwell, D. A.; Rajpaul, V. M.; Taylor, J.; Horner, J.; Eisner, N. L.; Lintott, C.; Miller, G.; Bean, S. J.; Bundy, D. M.; Peltsch, K.; Alhassan, S.; Baeten, E. M. L.; Goodwin, B. L.; Hoffman, T.; Nicholson, B. A.; Efremov, V.; Kaye, L.; Sporer, A.; Ferstenou, R.; Hof, M.; Hubert, A.; Lau, L.; Maetschke, D.; Rubio-Alfaro, C.; Wilson, G. M.
United Kingdom, Australia, Denmark, United States, Belgium, Canada
Abstract
We report on the discovery and validation of a two-planet system around a bright (V = 8.85 mag) early G dwarf (1.43 R⊙, 1.15 M⊙, TOI 2319) using data from NASA's Transiting Exoplanet Survey Satellite (TESS). Three transit events from two planets were detected by citizen scientists in the month-long TESS light curve (sector 25), as part of the Planet Hunters TESS project. Modelling of the transits yields an orbital period of $11.6264 _{ - 0.0025 } ^ { + 0.0022 }$ d and radius of $3.41 _{ - 0.12 } ^ { + 0.14 }$ R⊕ for the inner planet, and a period in the range 19.26-35 d and a radius of $5.83 _{ - 0.14 } ^ { + 0.14 }$ R⊕ for the outer planet, which was only seen to transit once. Each signal was independently statistically validated, taking into consideration the TESS light curve as well as the ground-based spectroscopic follow-up observations. Radial velocities from HARPS-N and EXPRES yield a tentative detection of planet b, whose mass we estimate to be $11.56 _{ - 6.14 } ^ { + 6.58 }$ M⊕, and allow us to place an upper limit of 27.5 M⊕ (99 per cent confidence) on the mass of planet c. Due to the brightness of the host star and the strong likelihood of an extended H/He atmosphere on both planets, this system offers excellent prospects for atmospheric characterization and comparative planetology.