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The NASA-UC Eta-Earth Program. II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses

Howard, Andrew W. and Johnson, John Asher and Marcy, Geoffrey W. and Fischer, Debra A. and Wright, Jason T. and Henry, Gregory W. and Isaacson, Howard and Valenti, Jeff A. and Anderson, Jay and Piskunov, Nikolai E. (2011) The NASA-UC Eta-Earth Program. II. A Planet Orbiting HD 156668 with a Minimum Mass of Four Earth Masses. Astrophysical Journal, 726 (2). Art. No. 73. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20110201-145242900

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Abstract

We report the discovery of HD 156668 b, an extrasolar planet with a minimum mass of M_P sin i = 4.15 M_⊕. This planet was discovered through Keplerian modeling of precise radial velocities from Keck-HIRES and is the second super-Earth to emerge from the NASA-UC Eta-Earth Survey. The best-fit orbit is consistent with circular and has a period of P = 4.6455 days. The Doppler semi-amplitude of this planet, K = 1.89 m s^(−1), is among the lowest ever detected, on par with the detection of GJ 581 e using HARPS. A longer period (P ≈ 2.3 years), low-amplitude signal of unknown origin was also detected in the radial velocities and was filtered out of the data while fitting the short-period planet. Additional data are required to determine if the long-period signal is due to a second planet, stellar activity, or another source. Photometric observations using the Automated Photometric Telescopes at Fairborn Observatory show that HD 156668 (an old, quiet K3 dwarf) is photometrically constant over the radial velocity period to 0.1 mmag, supporting the existence of the planet. No transits were detected down to a photometric limit of ~3 mmag, ruling out transiting planets dominated by extremely bloated atmospheres, but not precluding a transiting solid/liquid planet with a modest atmosphere.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/726/2/73DOIArticle
http://iopscience.iop.org/0004-637X/726/2/73/PublisherArticle
https://arxiv.org/abs/1003.3444arXivDiscussion Paper
ORCID:
AuthorORCID
Howard, Andrew W.0000-0001-8638-0320
Johnson, John Asher0000-0001-9808-7172
Marcy, Geoffrey W.0000-0002-2909-0113
Fischer, Debra A.0000-0003-2221-0861
Wright, Jason T.0000-0001-6160-5888
Henry, Gregory W.0000-0003-4155-8513
Isaacson, Howard0000-0002-0531-1073
Valenti, Jeff A.0000-0003-3305-6281
Additional Information:© 2011 The American Astronomical Society. Received 2010 March 16; accepted 2010 October 29; published 2010 December 16. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by both NASA and the University of California. We thank the many observers who contributed to the velocities reported here. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff, especially Scott Dahm, Hien Tran, and Grant Hill for support of HIRES and Greg Wirth for support of remote observing. We thank Heather Knutson, Doug Lin, Shigeru Ida, Jeff Scargle, and Ian Howard for helpful discussions. We are grateful to the time assignment committees of the University of California, NASA, and NOAO for their generous allocations of observing time. Without their long-term commitment to RV monitoring, these long-period planets would likely remain unknown. We acknowledge R. Paul Butler and S. S. Vogt for many years of contributing to the data presented here. A.W.H. gratefully acknowledges support from a Townes Post-doctoral Fellowship at the U. C. Berkeley Space Sciences Laboratory. G.W.M. acknowledges the NASA Grant NNX06AH52G. G.W.H. acknowledges support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. J.T.W. was partially supported by funding from the Center for Exoplanets and Habitable Worlds. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. This work made use of the SIMBAD database (operated at CDS, Strasbourg, France), NASA’s Astrophysics Data System Bibliographic Services, and the NASA Star and Exoplanet Database (NStED). Finally, the authors wish to extend special thanks to those of Hawai‘ian ancestry on whose sacred mountain of Mauna Kea we are privileged to be guests. Without their generous hospitality, the Keck observations presented herein would not have been possible.
Funders:
Funding AgencyGrant Number
UC Berkeley Space Sciences LaboratoryUNSPECIFIED
NSFUNSPECIFIED
Tennessee State UniversityUNSPECIFIED
State of TennesseeUNSPECIFIED
Center for Exoplanets and Habitable WorldsUNSPECIFIED
Pennsylvania State UniversityUNSPECIFIED
Eberly College of ScienceUNSPECIFIED
Pennsylvania Space Grant ConsortiumUNSPECIFIED
NASANNX06AH52G
Subject Keywords:planetary systems – stars: individual (HD 156668) – techniques: radial velocities
Issue or Number:2
Classification Code:PACS: 97.82.-j; 97.10.Kc; 97.20.Jg; 95.75.De
Record Number:CaltechAUTHORS:20110201-145242900
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20110201-145242900
Official Citation:Andrew W. Howard et al. 2011 ApJ 726 73 doi: 10.1088/0004-637X/726/2/73
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21955
Collection:CaltechAUTHORS
Deposited By: Benjamin Perez
Deposited On:02 Feb 2011 00:07
Last Modified:09 Mar 2020 13:19

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