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

Zhao, Bo; Weaver, Benjamin A.; Wan, Xiaoke; van Eyken, J. C.; Sivarani, Thirupathi; Simmons, Audrey; Shelden, Alaina; Schneider, Donald P.; Santiago, Basilio X.; Rebolo, R.; Allende-Prieto, C.; Paegert, Martin; Pepper, Joshua; Oravetz, Daniel; Ogando, Ricardo L. C.; Nguyen, Duy Cuong; Muna, Demitri; Maia, Marcio A. G.; Mahadevan, Suvrath; Liu, Jian; Li, Rui; Kane, Stephen R.; Jiang, Peng; Gary, Bruce; Eastman, Jason D.; Nicolaci da Costa, Luiz; Chang, Liang; Cargile, Phillip; Bizyaev, Dmitry; Agol, Eric; Wisniewski, John P.; Wang, Ji; Stassun, Keivan G.; Porto de Mello, G. F.; Lee, Brian L.; Gónzalez-Hernández, J. I.; Hebb, Leslie; Ghezzi, Luan; Gaudi, B. Scott; Fleming, Scott W.; Femenía, B.; Esposito, M.; Dutra-Ferreira, Leticia; De Lee, Nathan; Crepp, Justin R.; Barnes, Rory; Ge, Jian; Ma, Bo
Bibliographical reference

The Astronomical Journal, Volume 145, Issue 1, article id. 20, 15 pp. (2013).

Advertised on:
1
2013
Number of authors
48
IAC number of authors
5
Citations
12
Refereed citations
12
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, 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 &sun; 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 &sun; 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 rotsin 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.
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