KEPLER-21b: A ROCKY PLANET AROUND A V = 8.25 mag STAR
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 01238 (United States)
- SETI Institute, 189 Bernardo Avenue Suite 200, Mountain View, CA 94043 (United States)
- Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 01238 (United States)
- Centre for Star and Planet Formation, Natural History Museum of Denmark and Niels Bohr Institute, University of Copenhagen, DK-1350 Copenhagen (Denmark)
- Observatoire Astronomique de l’Université de Genéve, Chemin des Maillettes 51, Sauverny, CH-1290 (Switzerland)
- INAF—Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90124 Palermo (Italy)
- INAF—Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese (Italy)
- SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews Fife, KY16 9SS (United Kingdom)
- INAF—Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Alta (Spain)
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
- Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto (Portugal)
HD 179070, aka Kepler-21, is a V = 8.25 F6IV star and the brightest exoplanet host discovered by Kepler. An early detailed analysis by Howell et al. of the first 13 months (Q0–Q5) of Kepler light curves revealed transits of a planetary companion, Kepler-21b, with a radius of about 1.60 ± 0.04 R{sub ⊕} and an orbital period of about 2.7857 days. However, they could not determine the mass of the planet from the initial radial velocity (RV) observations with Keck-HIRES, and were only able to impose a 2σ upper limit of 10 M{sub ⊕}. Here, we present results from the analysis of 82 new RV observations of this system obtained with HARPS-N, together with the existing 14 HIRES data points. We detect the Doppler signal of Kepler-21b with a RV semiamplitude K = 2.00 ± 0.65 m s{sup −1}, which corresponds to a planetary mass of 5.1 ± 1.7 M{sub ⊕}. We also measure an improved radius for the planet of 1.639 +0.019/−0.015 R{sub ⊕}, in agreement with the radius reported by Howell et al. We conclude that Kepler-21b, with a density of 6.4 ± 2.1 g cm{sup −3}, belongs to the population of small, ≲6 M{sub ⊕} planets with iron and magnesium silicate interiors, which have lost the majority of their envelope volatiles via stellar winds or gravitational escape. The RV analysis presented in this paper serves as an example of the type of analysis that will be necessary to confirm the masses of TESS small planet candidates.
- OSTI ID:
- 22862832
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 152, Issue 6; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
Similar Records
TOI-1235 b: A Keystone Super-Earth for Testing Radius Valley Emergence Models around Early M Dwarfs
determining the mass of kepler-78b with nonparametric Gaussian process estimation