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

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 (MARVELS), 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, period P=9.0090+/-0.0004 days, and eccentricity e=0.226+/-0.011. Adopting a mass of 1.16+/-0.11 Msun 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 \sim1% level with a period of \sim13.16+/-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 Msun 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.

14 pages, 13 figures, accepted by AJ

References in corpus (24)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• Tertiary companions to close spectroscopic binaries
• Tidal Evolution of Close-in Extra-Solar Planets
• The first WASP public data release
• The Gemini Deep Planet Survey -- GDPS
• Tidal friction in close-in satellites and exoplanets. The Darwin theory re-visited
• The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
• A fast hybrid algorithm for exoplanetary transit searches
• Stellar Parameters and Metallicities of Stars Hosting Jovian and Neptunian Mass Planets: A Possible Dependence of Planetary Mass on Metallicity
• Hot Jupiters in binary star systems
• Extrasolar planets and brown dwarfs around A-F type stars VI. High precision RV survey of early type dwarfs with HARPS
• Metallicities & Activities of Southern Stars
• Constraining Orbital Parameters Through Planetary Transit Monitoring
• Interferometric Identification of a Pre-Brown Dwarf
• A Bayesian periodogram finds evidence for three planets in HD 11964
• Metallicities of Planet Hosting Stars: A Sample of Giants and Subgiants
• Theory of Dispersed Fixed-Delay Interferometry for Radial Velocity Exoplanet Searches
• Fourteen New Companions from the Keck & Lick Radial Velocity Survey Including Five Brown Dwarf Candidates
• HD 91669b: A New Brown Dwarf Candidate from the McDonald Observatory Planet Search
• Discovery of a Low-Mass Companion to a Metal-Rich F Star with the MARVELS Pilot Project
• The Empirical Mass-Luminosity Relation for Low Mass Stars
• Very Low-mass Stellar and Substellar Companions to Solar-like Stars from MARVELS II: A Short-period Companion Orbiting an F Star with Evidence of a Stellar Tertiary And Significant Mutual Inclination

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• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• Tidal Locking of Habitable Exoplanets
• Statistical Properties of Brown Dwarf Companions: Implications for Different Formation Mechanisms
• Companions to APOGEE Stars I: A Milky Way-Spanning Catalog of Stellar and Substellar Companion Candidates and their Diverse Hosts
• The SOPHIE search for northern extrasolar planets IX. Populating the brown dwarf desert
• Chemo-kinematics of the Milky Way from the SDSS-III MARVELS Survey
• Exploring the Brown Dwarf Desert: New Substellar Companions from the SDSS-III MARVELS Survey
• Very Low Mass Stellar and Substellar Companions to Solar-like Stars From MARVELS IV: A Candidate Brown Dwarf or Low-Mass Stellar Companion to HIP 67526
• Very Low Mass Stellar and Substellar Companions to Solar-Like Stars From MARVELS V: A Low Eccentricity Brown Dwarf from the Driest Part of the Desert, MARVELS-6b
• Very Low-Mass Stellar and Substellar Companions to Solar-like Stars From MARVELS VI: A Giant Planet and a Brown Dwarf Candidate in a Close Binary System HD 87646
• A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself To Be A Very Long Period, Highly Eccentric Spectroscopic Stellar Binary
• Accurate Atmospheric Parameters at Moderate Resolution Using Spectral Indices: Preliminary Application to the MARVELS Survey