Retired A Stars and Their Companions. IV. Seven Jovian Exoplanets from Keck Observatory
Abstract
We report precise Doppler measurements of seven subgiants from Keck Observatory. All seven stars show variability in their radial velocities consistent with planet-mass companions in Keplerian orbits. The host stars have masses ranging from 1.1 ≤ M_*/M_⊙ ≤ 1.9, radii 3.4 ≤ R_*/R_⊙ ≤ 6.1, and metallicities -0.21 ≤ [Fe/H] ≤ +0.26. The planets are all more massive than Jupiter (MP sin i > 1 M_(Jup)) and have semimajor axes a > 1 AU. We present millimagnitude photometry from the T3 0.4 m APT at Fairborn Observatory for five of the targets. Our monitoring shows these stars to be photometrically stable, further strengthening the interpretation of the observed radial velocity variability. The orbital characteristics of the planets thus far discovered around former A-type stars are very different from the properties of planets around dwarf stars of spectral type F, G, and K, and suggests that the formation and migration of planets is a sensitive function of stellar mass. Three of the planetary systems show evidence of long-term, linear trends indicative of additional distant companions. These trends, together with the high planet masses and increased occurrence rate, indicate that A-type stars are very promising targets for direct-imaging surveys.
Additional Information
© 2010 The Astronomical Society of the Pacific. Received 2009 December 28; accepted 2010 April 29; published 2010 May 19. 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 observations reported here. We gratefully acknowledge the efforts and dedication of the Keck Observatory staff, especially Grant Hill, Scott Dahm, and Hien Tran for their support of HIRES and Greg Wirth for support of remote observing. We are also grateful to the time assignment committees of NASA, NOAO, Caltech, and the University of California for their generous allocations of observing time. A. W. H. gratefully acknowledges support from a Townes Postdoctoral Fellowship at the U.C. Berkeley Space Sciences Laboratory. J. A. J. thanks the NSF Astronomy and Astrophysics Postdoctoral Fellowship program for support in the years leading to the completion of this work, and acknowledges support from NSF grant AST-0702821 and the NASA Exoplanets Science Institute (NExScI). G. W. M. acknowledges NASA grant NNX06AH52G. J. T.W. received support from NSF grant AST-0504874. G. W. H acknowledges support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. Finally, we 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.Attached Files
Published - Johnson2010p10321Publ_Astron_Soc_Pac.pdf
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Additional details
- Eprint ID
- 18698
- Resolver ID
- CaltechAUTHORS:20100616-084435213
- University of California
- AST-0702821
- NSF
- AST-0504874
- NSF
- NNX06AH52G
- NASA
- Tennessee State University
- State of Tennessee Centers of Excellence program
- Created
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2010-07-15Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field