HD 213885b: a transiting 1-d-period super-Earth with an Earth-like composition around a bright (V = 7.9) star unveiled by TESS
Henning, Thomas; Law, Nicholas M.; Jordán, Andrés; Espinoza, Néstor; Kossakowski, Diana; Brahm, Rafael; Wheatley, Peter J.; Bayliss, Daniel; Schlecker, Martin; Ziegler, Carl; Collins, Karen A.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Armstrong, David J.; Jenkins, James S.; Udry, Stéphane; Mann, Andrew W.; Jensen, Eric L. N.; Kielkopf, John F.; Twicken, Joseph D.; Bryant, Edward M.; Daylan, Tansu; Crossfield, Ian; Guerrero, Natalia; Bouchy, François; Nielsen, Louise D.; Barrado, David; Pepe, Francesco; Sarkis, Paula; Ricker, George; Díaz, Matías R.; Tokovinin, A.; Doty, John P.; Wingham, Geof; Lillo-Box, Jorge; Lovis, Christophe; Henze, Christopher E.; Figueira, Pedro; Adibekyan, Vardan; Dumusque, Xavier; Santos, Nuno C.; Briceño, C.; Demangeon, Olivier D. S.; Pollacco, Don; Hełminiak, Krzysztof G.; Ségransan, Damien; Barros, Susana C. C.; Morris, Robert L.; Boyd, Patricia; Turner, Oliver; Dorn, Caroline; Rojas, Felipe; Latham, David; Cooke, Benjamin F.; Marmier, Maxime; Sousa, Sergio G.; Hart, Rhodes; Lissauer, Jack; Battley, Matthew; Giles, Helen; Aguilera-Gomez, Claudia; Chacon, Aaron Dean
United States, Germany, Chile, Switzerland, United Kingdom, Portugal, Spain, Australia, New Zealand, Poland, Canada
Abstract
We report the discovery of the 1.008-d, ultrashort period (USP) super-Earth HD 213885b (TOI-141b) orbiting the bright (V = 7.9) star HD 213885 (TOI-141, TIC 403224672), detected using photometry from the recently launched TESS mission. Using FEROS, HARPS, and CORALIE radial velocities, we measure a precise mass of 8.8 ± 0.6 M⊕ for this 1.74 ± 0.05 R⊕ exoplanet, which provides enough information to constrain its bulk composition - similar to Earth's but enriched in iron. The radius, mass, and stellar irradiation of HD 213885b are, given our data, very similar to 55 Cancri e, making this exoplanet a good target to perform comparative exoplanetology of short period, highly irradiated super-Earths. Our precise radial velocities reveal an additional 4.78-d signal which we interpret as arising from a second, non-transiting planet in the system, HD 213885c, whose minimum mass of 19.9 ± 1.4 M⊕ makes it consistent with being a Neptune-mass exoplanet. The HD 213885 system is very interesting from the perspective of future atmospheric characterization, being the second brightest star to host an USP transiting super-Earth (with the brightest star being, in fact, 55 Cancri). Prospects for characterization with present and future observatories are discussed.