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Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants

Johnson, John Asher and Fischer, Debra A. and Marcy, Geoffrey W. and Wright, Jason T. and Driscoll, Peter and Butler, R. Paul and Hekker, Saskia and Reffert, Sabine and Vogt, Steven S. (2007) Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants. Astrophysical Journal, 665 (1). pp. 785-793. ISSN 0004-637X.

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We report precision Doppler measurements of three intermediate-mass subgiants obtained at Lick and Keck Observatories. All three stars show variability in their radial velocities consistent with planet-mass companions in Keplerian orbits. We find a planet with a minimum mass M_P sin i = 2.5 M_J in a 351.5 day orbit around HD 192699, a planet with a minimum mass of 2.0 M_J in a 341.1 day orbit around HD 210702, and a planet with a minimum mass of 0.61 M_J in a 297.3 day orbit around HD 175541. Mass estimates from stellar interior models indicate that all three stars were formerly A-type, main-sequence dwarfs with masses ranging from 1.65 to 1.85 M_☉. These three long-period planets would not have been detectable during their stars' main-sequence phases due to the large rotational velocities and stellar jitter exhibited by early-type dwarfs. There are now nine "retired" (evolved) A-type stars (M_* > 1.6 M_☉) with known planets. All nine planets orbit at distances ɑ ≥ 0.78 AU, which is significantly different from the semimajor axis distribution of planets around lower mass stars.

Item Type:Article
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URLURL TypeDescription
Johnson, John Asher0000-0001-9808-7172
Fischer, Debra A.0000-0003-2221-0861
Marcy, Geoffrey W.0000-0002-2909-0113
Wright, Jason T.0000-0001-6160-5888
Hekker, Saskia0000-0002-1463-726X
Additional Information:© 2007 American Astronomical Society. Received 2007 February 13; accepted 2007 May 8. Based on observations obtained at the Lick Observatory, which is operated by the University of California, and W.M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. We extend our gratitude to the many CAT observers who have helped with this project, including Howard Isaacson, Julia Kregenow, Karin Sandstrom, Bernie Walp, Peter Williams, Katie Peek, and Shannon Patel. Special thanks to Hervé Bouy and Francisco Ramos-Stierle for lending a portion of their 3 m observing time to observe HD 192699 before it set in 2006. We thank Michael Fitzgerald and Marshall Perrin for their useful discussions, and Tim Robishaw for sharing his data display expertise and IDL plotting routines. We also gratefully acknowledge the efforts and dedication of the Lick Observatory and Keck Observatory staff, and the time assignment committees of NASA, NOAO, and University of California for their generous allocations of observing time. We appreciate funding from NASA grant NNG05GK92G (to G. W. M.), and the NSF for its grant AST 03-07493 (to S. S. V.) for supporting this research. D. A. F. is a Cottrell Science Scholar of Research Corporation and acknowledges support from NASA Grant NNG05G164G that made this work possible. This research has made use of the Simbad database operated at CDS, Strasbourg France, and the NASA ADS database. The authors wish to extend special thanks to those of Hawaiian 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.
Funding AgencyGrant Number
NSFAST 03-07493
Issue or Number:1
Record Number:CaltechAUTHORS:20130104-143619750
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Official Citation: Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants John Asher Johnson et al. 2007 ApJ 665 785
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36183
Deposited By: Ruth Sustaita
Deposited On:04 Jan 2013 22:54
Last Modified:09 Mar 2020 13:18

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