TY - JOUR
T1 - KEPLER-21b: A ROCKY PLANET AROUND A v = 8.25 mag STAR
AU - López-Morales, Mercedes
AU - Haywood, Raphaëlle D.
AU - Coughlin, Jeffrey L.
AU - Zeng, Li
AU - Buchhave, Lars A.
AU - Giles, Helen A.C.
AU - Affer, Laura
AU - Bonomo, Aldo S.
AU - Charbonneau, David
AU - Cameron, Andrew Collier
AU - Consentino, Rosario
AU - Dressing, Courtney D.
AU - Dumusque, Xavier
AU - Figueira, Pedro
AU - Fiorenzano, Aldo F. M.
AU - Harutyunyan, Avet
AU - Johnson, John Asher
AU - Latham, David W.
AU - Lopez, Eric D.
AU - Lovis, Christophe
AU - Malavolta, Luca
AU - Mayor, Michel
AU - Micela, Giusi
AU - Molinari, Emilio
AU - Mortier, Annelies
AU - Motalebi, Fatemeh
AU - Nascimbeni, Valerio
AU - Pepe, Francesco
AU - Phillips, David F.
AU - Piotto, Giampaolo
AU - Pollacco, Don
AU - Queloz, Didier
AU - Rice, Ken
AU - Sasselov, Dimitar
AU - Segransan, Damien
AU - Sozzetti, Alessandro
AU - Udry, Stephane
AU - Vanderburg, Andrew
AU - Watson, Chris
PY - 2016/12/1
Y1 - 2016/12/1
N2 - 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 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 . 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 ± 0.65ms-1, which corresponds to a planetary mass of 5.1 ± 1.7 M⊕ We also measure an improved radius for the planet of 1.639 +0.019/-0.015 R⊕, 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-1, belongs to the population of small, ≲6 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.
AB - 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 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 . 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 ± 0.65ms-1, which corresponds to a planetary mass of 5.1 ± 1.7 M⊕ We also measure an improved radius for the planet of 1.639 +0.019/-0.015 R⊕, 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-1, belongs to the population of small, ≲6 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.
KW - planets and satellites: formation
KW - planets and satellites: individual (Kepler-21b)
KW - stars: individual (HD 179070)
KW - techniques: photometric
KW - techniques: radial velocities
KW - techniques: spectroscopic
UR - http://www.scopus.com/inward/record.url?scp=85009101111&partnerID=8YFLogxK
U2 - 10.3847/0004-6256/152/6/204
DO - 10.3847/0004-6256/152/6/204
M3 - Article
AN - SCOPUS:85009101111
SN - 0004-6256
VL - 152
JO - Astronomical Journal
JF - Astronomical Journal
IS - 6
M1 - 204
ER -