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Register a new userThe PHASES Differential Astrometry Data Archive IV: The Triple Star Systems 63 Gem A and HR 2896
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Added by
Matthew Muterspaugh
Publication date
2010
fields
Physics
and research's language is
English
Authors
Matthew W. Muterspaugh
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(Abridged) 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 lesssim 2 day subsystem in the triple system 63 Gem A and have detected a previously unknown 2 year Keplerian wobble superimposed on the visual orbit of the much longer period (213 years) binary system HR 2896. 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 objects mass estimate places it in the regime of being a 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 timeframe 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 pm 12 degrees or a less likely value of 31 pm 11 degrees for 63 Gem A and 10.2 pm 2.4 degrees or 171.2 pm 2.8 degrees for HR 2896. The first is not coplanar, whereas the second is either nearly coplanar or anti-coplanar.
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The Palomar High-precision Astrometric Search for Exoplanet Systems monitored 51 subarcsecond binary systems to evaluate whether tertiary companions as small as Jovian planets orbited either the primary or secondary stars, perturbing their otherwise smooth Keplerian motions. Six binaries are presented that show evidence of substellar companions orbiting either the primary or secondary star. Of these six systems, the likelihoods of two of the detected perturbations to represent real objects are considered to be high confidence, while the remaining four systems are less certain and will require continued observations for confirmation.
Differential astrometry measurements from the Palomar High-precision Astrometric Search for Exoplanet Systems have been combined with lower precision single-aperture measurements covering a much longer timespan (from eyepiece measurements, speckle interferometry, and adaptive optics) to determine improved visual orbits for 20 binary stars. In some cases, radial velocity observations exist to constrain the full three-dimensional orbit and determine component masses. The visual orbit of one of these binaries---alpha Com (HD 114378)---shows that the system is likely to have eclipses, despite its very long period of 26 years. The next eclipse is predicted to be within a week of 2015 January 24.
The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) monitored 51 sub-arcsecond binary systems to determine precision binary orbits, study the geometries of triple and quadruple star systems, and discover previously unknown faint astrometric companions as small as giant planets. PHASES measurements made with the Palomar Testbed Interferometer (PTI) from 2002 until PTI ceased normal operations in late 2008 are presented. Infrared differential photometry of several PHASES targets were measured with Keck Adaptive Optics and are presented.
The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) monitored 51 subarcsecond binary systems to evaluate whether tertiary companions as small as Jovian planets orbited either the primary or secondary stars, perturbing their otherwise smooth Keplerian motions. Twenty-one of those systems were observed 10 or more times and show no evidence of additional companions. A new algorithm is presented for identifying astrometric companions and establishing the (companion mass)-(orbital period) combinations that can be excluded from existence with high confidence based on the PHASES observations, and the regions of mass-period phase space being excluded are presented for 21 PHASES binaries.
We have used multi-epoch long-baseline radio interferometry to determine the proper motion and orbital elements of Algol and UX Arietis, two radio-bright, close binary stellar systems with distant tertiary components. For Algol, we refine the proper motion and outer orbit solutions, confirming the recent result of Zavala et al. (2010) that the inner orbit is retrograde. The radio centroid closely tracks the motion of the KIV secondary. In addition, the radio morphology varies from double-lobed at low flux level to crescent-shaped during active periods. These results are most easily interpreted as synchrotron emission from a large, co-rotating meridional loop centered on the K-star. If this is correct, it provides a radio-optical frame tie candidate with an uncertainty {pm}0.5 mas. For UX Arietis, we find a outer orbit solution that accounts for previous VLBI observations of an acceleration term in the proper motion fit. The outer orbit solution is also consistent with previously published radial velocity curves and speckle observations of a third body. The derived tertiary mass, 0.75 solar masses, is consistent with the K1 main-sequence star detected spectroscopically. The inner orbit solution favors radio emission from the active K0IV primary only. The radio morphology, consisting of a single, partially resolved emission region, may be associated with the persistent polar spot observed using Doppler imaging.
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