Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor
Abstract
The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of ~6 J- and H-band magnitudes and separation of 1" from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star to <=3 milliarcsecond precision at two observation epochs. Our measurements demonstrate common parallactic and proper motion over the course of 103 days, significantly shorter than the period of time needed for most companion confirmations through proper motion measurements alone. This common parallax method is potentially more rigorous than common proper motion, ensuring that the neighboring bodies lie at the same distance, rather than relying on the statistical improbability that two objects in close proximity to each other on the sky move in the same direction. The discovery of a low-mass (~0.25M_sun) companion around a bright (V = 4.0), nearby (d = 25 pc) star highlights a region of binary star parameter space that to date has not been fully probed.
Cite
@article{arxiv.0912.1597,
title = {Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor},
author = {Neil Zimmerman and Ben R. Oppenheimer and Sasha Hinkley and Douglas Brenner and Ian R. Parry and Anand Sivaramakrishnan and Lynne Hillenbrand and Charles Beichman and Justin R. Crepp and Gautam Vasisht and Lewis C. Roberts and Rick Burruss and David L. King and Rémi Soummer and Richard Dekany and Michael Shao and Antonin Bouchez and Jennifer E. Roberts and Stephanie Hunt},
journal= {arXiv preprint arXiv:0912.1597},
year = {2014}
}
Comments
submitted to ApJ on Nov 11, 2009; accepted for publication in ApJ on Dec 7, 2009; 10 pages, 3 figures