THE PHASES DIFFERENTIAL ASTROMETRY DATA ARCHIVE. IV. THE TRIPLE STAR SYSTEMS 63 Gem A AND HR 2896
- Department of Mathematics and Physics, College of Arts and Sciences, Tennessee State University, Boswell Science Hall, Nashville, TN 37209 (United States)
- Tennessee State University, Center of Excellence in Information Systems, 3500 John A. Merritt Blvd., Box No. 9501, Nashville, TN 37209-1561 (United States)
- Draper Laboratory, 555 Technology Square, Cambridge, MA 02139-3563 (United States)
- U.S. Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 (United States)
- Division of Physics, Mathematics and Astronomy, 105-24, California Institute of Technology, Pasadena, CA 91125 (United States)
- Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Rabianska 8, 87-100 Torun (Poland)
- MIT Kavli Institute for Astrophysics and Space Research, MIT Department of Physics, 70 Vassar Street, Cambridge, MA 02139 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)
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 {approx}<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{sup 0} {+-} 12{sup 0} or a less likely value of 31{sup 0} {+-} 11{sup 0} for 63 Gem A and 10.{sup 0}2 {+-} 2.{sup 0}4 or 171.{sup 0}2 {+-} 2.{sup 0}8 for HR 2896. The first is not coplanar, whereas the second is either nearly coplanar or anti-coplanar.
- OSTI ID:
- 21443177
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 140, Issue 6; Other Information: DOI: 10.1088/0004-6256/140/6/1646; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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