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 (The Astronomical Journal, 2012)

• Rory Barnes

Full Citation:
Ma, B., 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., de Mello, G. F. P., Stassun, K. G., Wang, J., Wisniewski, J. P., Agol, E., … Zhao, B. (2012). 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. The Astronomical Journal, 145(1), 20. https://doi.org/10.1088/0004-6256/145/1/20

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.

URL:
https://iopscience.iop.org/article/10.1088/0004-6256/145/1/20

VPL Research Tasks:
Task E: The Observer