Characterization of the Companion to μ Her

Creators: Roberts, Lewis C., Jr.; Beichman, Charles; Dekany, Richard; Hillenbrand, Lynne

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Abstract

μ Her is a nearby quadruple system with a G-subgiant primary and several low-mass companions arranged in a 2+2 architecture. While the BC components have been well characterized, the Ab component has been detected astrometrically and with direct imaging but there has been some confusion over its nature, in particular, whether the companion is stellar or substellar. Using near-infrared spectroscopy, we are able to estimate the spectral type of the companion as an M4±1V star. In addition, we have measured the astrometry of the system for over a decade. We combined the astrometry with archival radial velocity measurements to compute an orbit of the system. From the combined orbit, we are able to compute the mass sum of the system. Using the estimated mass of the primary, we estimate the mass of the secondary as 0.32 M_☉, which agrees with the estimated spectral type. Our computed orbit is preliminary due to the incomplete orbital phase coverage, but it should be sufficient to predict ephemerides over the next decade.

Additional Information

© 2016 The American Astronomical Society. Received 2015 November 4; accepted 2016 April 20; published 2016 June 1. Our thanks to Nils Turner for assistance with the Mt. Wilson log books. We also thank Andrei Tokovinin for assistance with the latest version of his ORBITX code. A portion of the research in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). This work was partially funded through the NASA ROSES Origins of Solar Systems grant NMO710830/102190. Project 1640 is funded by National Science Foundation grants AST-0520822, AST-0804417, and AST-0908484. In addition, part of this work was performed under a contract with the California Institute of Technology funded by NASA through the Sagan Fellowship Program. J.A. is supported by the Laboratory for Physical Sciences, College Park, MD, through the National Physical Science Consortium graduate fellowship program. J.C. was supported by the U.S. National Science Foundation under Award No. 1009203. R.N. was funded by the Swedish Research Council's International Postdoctoral Grant No. 637-2013-474. The members of the Project 1640 team are also grateful for support from the Cordelia Corporation, Hilary and Ethel Lipsitz, the Vincent Astor Fund, Judy Vale, Andrew Goodwin, and an anonymous donor. This paper is based on observations obtained at the Maui Space Surveillance System operated by the US Air Force Research Laboratory's Directed Energy Directorate and at the Hale Telescope, Palomar Observatory. This research made use of the Keck Observatory Archive (KOA), which is operated by the W.M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. NExScI is sponsored by NASA's Origins Theme and Exoplanet Exploration Program, and operated by the California Institute of Technology in coordination with the Jet Propulsion Laboratory. This research made use of the Washington Double Star Catalogue maintained at the U.S. Naval Observatory, the SIMBAD database, operated by the CDS in Strasbourg, France and NASA's Astrophysics Data System. Facility: AEOS (Visible Imager), Hale (Project 1640, PHARO), Keck:II (NIRSPEC).

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