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Post Info TOPIC: Kepler-21b
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RE: Kepler-21b
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Title: Kepler-21b: A rocky planet around a V = 8.25 magnitude star.
Author: Mercedes Lopez-Morales, Raphaelle D. Haywood, Jeffrey L. Coughlin, Li Zeng, Lars A. Buchhave, Helen A. C. Giles, Laura Affer, Aldo S. Bonomo, David Charbonneau, Andrew Collier Cameron, Rosario Cosentino, Courtney D. Dressing, Xavier Dumusque, Pedro Figueira, Aldo F. M. Fiorenzano, Avet Harutyunyan, John Asher Johnson, David W. Latham, Eric D. Lopez, Christophe Lovis, Luca Malavolta, Michel Mayor, Giusi Micela, Emilio Molinari, Annelies Mortier, Fatemeh Motalebi, Valerio Nascimbeni, Francesco Pepe, David F. Phillips, Giampaolo Piotto, Don Pollacco, Didier Queloz, Ken Rice, Dimitar Sasselov, Damien Segransan, Alessandro Sozzetti, Stephane Udry, Andrew Vanderburg, Chris Watson

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. (2012) of the first thirteen 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_earth and an orbital period of about 2.7857 days. However, they could not determine the mass of the planet from the initial radial velocity observations with Keck-HIRES, and were only able to impose a 2-sigma upper limit of 10 M_earth. Here we present results from the analysis of 82 new radial velocity 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 radial velocity semi-amplitude K = 2.00 ± 0.65 m/s, which corresponds to a planetary mass of 5.1 ± 1.7 M_earth. We also measure an improved radius for the planet of 1.639 (+0.019, -0.015) R_earth, in agreement with the radius reported by Howell et al. (2012). We conclude that Kepler-21b, with a density of 6.4 ± 2.1 g/cm³, belongs to the population of terrestrial planets with iron, magnesium silicate interiors, which have lost the majority of their envelope volatiles via stellar winds or gravitational escape. The radial velocity analysis presented in this paper serves as example of the type of analysis that will be necessary to confirm the masses of TESS small planet candidates.

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Blobrana


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HD 179070
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Title: Validation of the Exoplanet Kepler-21b using PAVO/CHARA Long-Baseline Interferometry
Authors: Daniel Huber, Michael J. Ireland, Timothy R. Bedding, Steve B. Howell, Vicente Maestro, Antoine Mérand, Peter G. Tuthill, Timothy R. White, Christopher D. Farrington, P. J. Goldfinger, Harold A. McAlister, Gail H. Schaefer, Judit Sturmann, Laszlo Sturmann, Theo A. ten Brummelaar, Nils H. Turner

We present long-baseline interferometry of the Kepler exoplanet host star HD179070 (Kepler-21) using the PAVO beam combiner at the CHARA Array. The visibility data are consistent with a single star and exclude stellar companions at separations ~1-1000 mas (~ 0.1-113 AU) and contrasts < 3.5 magnitudes. This result supports the validation of the 1.6 R_{earth} exoplanet Kepler-21b by Howell et al. (2012) and complements the constraints set by adaptive optics imaging, speckle interferometry, and radial velocity observations to rule out false-positives due to stellar companions. We conclude that long-baseline interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial velocity follow-up is not available.

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Blobrana


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Title: Kepler-21b: A 1.6REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070
Authors: Steve B. Howell, Jason F. Rowe, Stephen T. Bryson, Samuel N. Quinn, Geoffrey W. Marcy, Howard Isaacson, David R. Ciardi, William J. Chaplin, Travis S. Metcalfe, Mario J. P. F. G. Monteiro, Thierry Appourchaux, Sarbani Basu, Orlagh L. Creevey, Ronald L. Gilliland, Pierre-Olivier Quirion, Denis Stello, Hans Kjeldsen, Jorgen Christensen-Dalsgaard, Yvonne Elsworth, Rafael A. García, Gunter Houdek, Christoffer Karoff, Joanna Molenda-akowicz, Michael J. Thompson, Graham A. Verner, Guillermo Torres, Francois Fressin, Justin R. Crepp, Elisabeth Adams, Andrea Dupree, Dimitar D. Sasselov, Courtney D. Dressing, William J. Borucki, David G. Koch, Jack J. Lissauer, David W. Latham, Thomas N. Gautier III, Mark Everett, Elliott Horch, Natalie M. Batalha, Edward W. Dunham, Paula Szkody, David R. Silva, et al. (23 additional authors not shown)

We present Kepler observations of the bright (V=8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R_Earth object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequencypower spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34 ±0.06 solar masses and 1.86 ±0.04 solar radii respectively, as well as yielding an age of 2.84 ±0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3{\sigma}) that the transit event is caused by a 1.64 ±0.04 Earth radii exoplanet in a 2.785755 ±0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of ~10 M_Earth (2-{\sigma}). HD 179070 is the brightest exoplanet host star yet discovered by Kepler.

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New Planet Kepler-21b discovery a partnership of both space and ground-based observations

The NASA Kepler Mission is designed to survey a portion of our region of the Milky Way Galaxy to discover Earth-size planets in or near the "habitable zone," the region in a planetary system where liquid water can exist, and determine how many of the billions of stars in our galaxy have such planets. It now has another planet to add to its growing list. A research team led by Steve Howell, NASA Ames Research Centre, has shown that one of the brightest stars in the Kepler star field has a planet with a radius only 1.6 that of the earth's radius and a mass no greater that 10 earth masses, circling its parent star with a 2.8 day period. With such a short period, and such a bright star, the team of over 65 astronomers (that included David Silva, Ken Mighell and Mark Everett of NOAO) needed multiple telescopes on the ground to support and confirm their Kepler observations. These included the 4 meter Mayall telescope and the WIYN telescope at Kitt Peak National Observatory. The accompanying figure shows the size of the Kepler field, seen over Kitt Peak.
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