Muterspaugh, Matthew W. and Fekel, Francis C. and Lane, Benjamin F. and Hartkopf, William I. and Kulkarni, S. R. and Konacki, Maciej and Burke, Bernard F. and Colavita, M. M. and Shao, M. and Williamson, M. (2010) The Phases Differential Astrometry Data Archive. IV. The Triple Star Systems 63 Gem A and HR 2896. Astronomical Journal, 140 (6). pp. 1646-1656. ISSN 0004-6256 http://resolver.caltech.edu/CaltechAUTHORS:20101216-141817259
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Differential astrometry measurements from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) are used to constrain the astrometric orbit of the previously known ≾2 day subsystem in the triple system 63 Gem A and have detected a previously unknown two-year Keplerian wobble superimposed on the visual orbit of the much longer period (213 years) binary system HR 2896. 63 Gem A was already known to be triple from spectroscopic work, and absorption lines from all three stars can be identified and their individual Doppler shifts measured; new velocities for all three components are presented to aid in constraining the orbit and measuring the stellar masses. In fact, 63 Gem itself is a sextuple system: the hierarchical triple (Aa1-Aa2)-Ab (in which Aa1 and Aa2 orbit each other with a rapid period just under 2 days, and Ab orbits these every two years), plus three distant common proper motion companions. The very small astrometric perturbation caused by the inner pair in 63 Gem A stretches the limits of current astrometric capabilities, but PHASES observations are able to constrain the orientation of the orbit. The two bright stars comprising the HR 2896 long-period (213 year) system have a combined spectral type of K0III and the newly detected object's mass estimate places it in the regime of being an M dwarf. The motion of the stars are slow enough that their spectral features are always blended, preventing Doppler studies. The PHASES measurements and radial velocities (when available) have been combined with lower precision single-aperture measurements covering a much longer time frame (from eyepiece measurements, speckle interferometry, and adaptive optics) to improve the characterization of the long-period orbits in both binaries. The visual orbits of the short- and long-period systems are presented for both systems and used to calculate two possible values of the mutual inclinations between inner and outer orbits of 152° ± 12° or a less likely value of 31° ± 11° for 63 Gem A and 10.°2 ± 2.°4 or 171.°2 ± 2.°8 for HR 2896. The first is not coplanar, whereas the second is either nearly coplanar or anti-coplanar.
|Additional Information:||© 2010 The American Astronomical Society. Received 2010 July 8; accepted 2010 September 19; published 2010 October 20. PHASES benefits from the efforts of the PTI collaboration members who have each contributed to the development of an extremely reliable observational instrument. Without this outstanding engineering effort to produce a solid foundation, advanced phase-referencing techniques would not have been possible. We thank PTI’s night assistant Kevin Rykoski for his efforts to maintain PTI in excellent condition and operating PTI in phase-referencing mode every week. Thanks are also extended to Ken Johnston and the U. S. Naval Observatory for their continued support of the USNO Double Star Program. Part of the work described in this paper was performed at the Jet Propulsion Laboratory under contract with the National Aeronautics and Space Administration. Interferometer data were obtained at the Palomar Observatory with the NASA Palomar Testbed Interferometer, supported by NASA contracts to the Jet Propulsion Laboratory. This publication makes use of data products from the TwoMicronAll Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the Simbad database, operated at CDS, Strasbourg, France. This research has made use of SAOImage DS9, developed by the Smithsonian Astrophysical Observatory. M.W.M. acknowledges support from the Townes Fellowship Program, Tennessee State University, and the state of Tennessee through its Centers of Excellence program. Some of the software used for analysis was developed as part of the SIM Double Blind Test with support from NASA contract NAS7-03001 (JPL 1336910). PHASES is funded in part by the California Institute of Technology, Astronomy Department, and by the National Aeronautics and Space Administration under Grant No. NNG05GJ58G issued through the Terrestrial Planet Finder Foundation Science Program. This work was supported in part by the National Science Foundation through grants AST 0300096, AST 0507590, and AST 0505366. M.K. is supported by the Foundation for Polish Science through a FOCUS grant and fellowship, by the Polish Ministry of Science and Higher Education through grant N203 3020 35. Facilities: PO:PTI, TSU:AST, KPNO:CFT|
|Subject Keywords:||astrometry; binaries: close; binaries: visual|
|Classification Code:||PACS: 97.80.Fk; 95.85.Kr; 97.10.Nf; 97.80.Di; 95.10.Jk|
|Official Citation:||Matthew W. Muterspaugh et al 2010 The Astronomical Journal 140 1646 doi: 10.1088/0004-6256/140/6/1646|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||17 Dec 2010 18:07|
|Last Modified:||26 Dec 2012 12:46|
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