Very-low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels. III. A Short-period Brown Dwarf Candidate around an Active G0IV Subgiant

Creators: Ma, Bo; Crepp, Justin R.; Kane, Stephen R.; van Eyken, J. C.

Abstract

We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T_(eff) = 5903 ± 42 K, surface gravity log (g) = 4.07 ± 0.16 (cgs), and metallicity [Fe/H] = -0.23 ± 0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey, which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 3.571 ± 0.041 km s^(–1), period P = 9.0090 ± 0.0004 days, and eccentricity e = 0.226 ± 0.011. Adopting a mass of 1.16 ± 0.11 M_☉ for the subgiant host star, we infer that the companion has a minimum mass of 40.0 ± 2.5 M_(Jup). Assuming an edge-on orbit, the semimajor axis is 0.090 ± 0.003 AU. The host star is photometrically variable at the ~1% level with a period of ~13.16 ± 0.01 days, indicating that the host star spin and companion orbit are not synchronized. Through adaptive optics imaging we also found a point source 643 ± 10 mas away from TYC 2087-00255-1, which would have a mass of 0.13 M_☉ if it is physically associated with TYC 2087-00255-1 and has the same age. Future proper motion observation should be able to resolve if this tertiary object is physically associated with TYC 2087-00255-1 and make TYC 2087-00255-1 a triple body system. Core Ca II H and K line emission indicate that the host is chromospherically active, at a level that is consistent with the inferred spin period and measured v_(rot) sin i, but unusual for a subgiant of this T_(eff). This activity could be explained by ongoing tidal spin-up of the host star by the companion.

Additional Information

© 2013 American Astronomical Society. Received 2012 June 26; accepted 2012 November 2; published 2012 December 12. Funding for the MARVELS multi-object Doppler instrument was provided by the W.M. Keck Foundation and NSF with grant AST-0705139. The MARVELS survey was partially funded by the SDSS-III consortium, NSF grant AST-0705139, NASA with grant NNX07AP14G, and the University of Florida. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III Web site is http://www.sdss3.org/. SDSSIII is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. This work is based on observations collected at Observatόrio do Pico dos Dias (OPD), operated by the Laboratόrio Nacional de Astrofísica, CNPq, Brazil. FEROS spectra were observed at the ESO 2.2 m telescope under the ESO-ON agreement. This work has made use of observations taken with the Telescopio Nationale Galileo (TNG) operated on the island of La Palma by the Foundation Galileo Galilei, funded by the Instituto Nazionale di Astrofisica (INAF), in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). This research is 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. Keivan Stassun, Leslie Hebb, and Joshua Pepper acknowledge funding support from the Vanderbilt Initiative in Data-Intensive Astrophysics (VIDA) from Vanderbilt University, and from NSF Career award AST-0349075. E.A. thanks NSF for CAREER grant 0645416. G.F.P.M. acknowledges financial support from CNPq grant No.476909/2006-6 and FAPERJ grant No. APQ1/26/170.687/2004. L.G. acknowledges financial support provided by the PAPDRJ CAPES/FAPERJ Fellowship. J.P.W. acknowledges support from NSF Astronomy & Astrophysics Postdoctoral Fellowship AST 08-02230. L.D.F. acknowledges financial support from CAPES. R.B. acknowledges support from NSF AST grant 1108882. B.S.G. acknowledges funding support from NSF CAREER grant AST-105652. This research has benefitted from the M, L, and T dwarf compendium housed at DwarfArchives.org http://spider.ipac. caltech.edu/staff/davy/ARCHIVE/index.shtml) and maintained by Chris Gelino, Davy Kirkpatrick, and Adam Burgasser. We have used data from the WASP public archive in this research. The WASP consortium comprises of the University of Cambridge, Keele University, University of Leicester, The Open University, The Queen's University Belfast, St. Andrews University and the Isaac Newton Group. Funding for WASP comes from the consortium universities and from the UK's Science and Technology Facilities Council. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This publication makes use of data products from the Wide field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.

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