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: name: Ma, Bo
name: Ge, Jian
name: Barnes, Rory
name: Crepp, Justin R.
name: De Lee, Nathan
name: Dutra-Ferreira, Leticia
name: Esposito, Massimiliano
name: Femenia, Bruno
name: Fleming, Scott W.
name: Gaudi, B. Scott
name: Ghezzi, Luan
name: Hebb, Leslie
name: Hernandez, Jonay I. Gonzalez
name: Lee, Brian L.
name: de Mello, G. F. Porto
name: Stassun, Keivan G.
name: Wang, Ji
name: Wisniewski, John P.
name: Agol, Eric
name: Bizyaev, Dmitry
name: Cargile, Phillip
name: Chang, Liang
name: da Costa, Luiz Nicolaci
name: Eastman, Jason D.
name: Gary, Bruce
name: Jiang, Peng
name: Kane, Stephen R.
name: Li, Rui
name: Liu, Jian
name: Mahadevan, Suvrath
name: Maia, Marcio A. G.
name: Muna, Demitri
name: Nguyen, Duy Cuong
name: Ogando, Ricardo L. C.
name: Oravetz, Daniel
name: Pepper, Joshua
name: Paegert, Martin
name: Prieto, Carlos Allende
name: Rebolo, Rafael
name: Santiago, Basilio X.
name: Schneider, Donald P.
name: Shelden, Alaina
name: Simmons, Audrey
name: Sivarani, Thirupathi
name: van Eyken, J. C.
name: Wan, Xiaoke
name: Weaver, Benjamin A.
name: Zhao, Bo
Publisher: name: arXiv
Year: 2012
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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.
description: 14 pages, 13 figures, accepted by AJ