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Title: Very-Low-Mass Stellar and Substellar Companions to Solar-Like Stars From Marvels. III. A Short-period Brown Dwarf Candidate Around An Active GOIV Subgiant
Authors: Ma, Bo
Ge, J
Barnes, R
Crepp, J. R
De Lee, N
Dutra-Ferreira, L
Esposito, M
Femenia, B
Fleming, S. W
Gaudi, B. S
Ghezzi, L
Hebb, L
Gonzalez Hernandez, J. I
Lee, B. L
Porto de Mello, G. F
Stassun, K. G
Wang, J
Wisniewski, J. P
Agol, E
Bizyaev, D
Cargile, P
Chang, L
Nicolaci da Costa, L
Eastman, J. D
Gary, B
Jiang, P
Kane, S. R
Li, R
Liu, J
Mahadevan, S
Maia, M. A. G
Muna, D
Nguyen, D. C
Ogando, R. L. C
Oravetz, D
Pepper, J
Paegert, M
Prieto, C. A
Rebolo, R
Santiago, B. X
Schneider, D. P
Shelden, A
Simmons, A
Sivarani, T
van Eyken, J. C
Wan, X
Weaver, B. A
Zhao, Bo
Keywords: Brown dwarfs;Stars: low-mass;Techniques: radial velocities
Issue Date: Jan-2013
Publisher: IOP Publishing
Citation: The Astrophysical Journal, Vol. 145, No. 1, 20
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 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.
Description: Open Access
ISSN: 1742-6588
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Appears in Collections:IIAP Publications

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