Choi, Jieun and McCarthy, Chris and Marcy, Geoffrey W. and Howard, Andrew W. and Fischer, Debra A. and Johnson, John A. and Isaacson, Howard and Wright, Jason T. (2013) Precise Doppler Monitoring of Barnard's Star. Astrophysical Journal, 764 (2). Art. No. 131. ISSN 0004-637X. http://resolver.caltech.edu/CaltechAUTHORS:20130327-131557551
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We present 248 precise Doppler measurements of Barnard's Star (Gl 699), the second nearest star system to Earth, obtained from Lick and Keck Observatories during the 25 years between 1987 and 2012. The early precision was 20 m s^(–1) but was 2 m s^(–1) during the last 8 years, constituting the most extensive and sensitive search for Doppler signatures of planets around this stellar neighbor. We carefully analyze the 136 Keck radial velocities spanning 8 years by first applying a periodogram analysis to search for nearly circular orbits. We find no significant periodic Doppler signals with amplitudes above ~2 m s^(–1), setting firm upper limits on the minimum mass (M sin i) of any planets with orbital periods from 0.1 to 1000 days. Using a Monte Carlo analysis for circular orbits, we determine that planetary companions to Barnard's Star with masses above 2 M_⊕ and periods below 10 days would have been detected. Planets with periods up to 2 years and masses above 10 M_⊕ (0.03 M_(Jup)) are also ruled out. A similar analysis allowing for eccentric orbits yields comparable mass limits. The habitable zone of Barnard's Star appears to be devoid of roughly Earth-mass planets or larger, save for face-on orbits. Previous claims of planets around the star by van de Kamp are strongly refuted. The radial velocity of Barnard's Star increases with time at 4.515 ± 0.002 m s^(–1) yr^(–1), consistent with the predicted geometrical effect, secular acceleration, that exchanges transverse for radial components of velocity.
|Additional Information:||© 2013 American Astronomical Society. Received 2012 May 8; accepted 2012 December 17; published 2013 January 31. Based on observations made at Keck Observatory and Lick Observatory. This work made use of the Exoplanet Orbit Database and the Exoplanet Data Explorer at www.exoplanets.org. We thank our referee, Martin Kürster, for his valuable suggestions, and Jennifer Bartlett and Joshua Burkart for much helpful input. We acknowledge support by NASA grants NAG5-8299, NNX11AK04A, and NSF grant AST95-20443 (to GWM), and by Sun Microsystems. We also thank the Watson and Marilyn Albert SETI Chair fund, and Howard and Astrid Preston for generous donations making this research possible. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program; NASA’s Astrophysics Data System, and the SIMBAD database, operated at CDS, Strasbourg, France; and the Exoplanet Orbit Database and the Exoplanet Data Explorer at www.exoplanets.org. 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. We thank R. Paul Butler and Steven Vogt for help making observations. We thank the W. M. Keck Observatory and Lick Observatory for their generous allocations of telescope time, and we thank the State of California for its support of operations at both observatories. We thank the W. M. Keck Foundation and NASA for support that made the Keck Observatory possible. We thank the indigenous Hawaiian people for the use of their sacred mountain, Mauna Kea.|
|Subject Keywords:||stars: individual (Gl 699); techniques: radial velocities|
|Official Citation:||Precise Doppler Monitoring of Barnard's Star Jieun Choi et al. 2013 ApJ 764 131|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||27 Mar 2013 22:28|
|Last Modified:||27 Mar 2013 22:28|
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