Cool Companions to White Dwarf Stars from the Two Micron All Sky Survey All Sky Data Release

Creators: Hoard, D. W.; Wachter, S.; Sturch, Laura K.; Widhalm, Allison M.; Weiler, Kevin P.; Pretorius, Magaretha L.; Wellhouse, Joseph W.; Gibiansky, Maxsim

Abstract

We present the culmination of our near-infrared survey of the optically spectroscopically identified white dwarf stars from the McCook and Sion catalog, conducted using photometric data from the Two Micron All Sky Survey final All Sky Data Release. The color selection technique, which identifies candidate binaries containing a white dwarf and a low-mass stellar (or substellar) companion via their distinctive locus in the near-infrared color-color diagram, is demonstrated to be simple to apply and to yield candidates with a high rate of subsequent confirmation. We recover 105 confirmed binaries, and identify 27 firm candidates (19 of which are new to this work) and 21 tentative candidates (17 of which are new to this work) from the 2MASS data. Only a small number of candidates from our survey have likely companion spectral types later than M5, none of which is an obvious L-type (i.e., potential brown dwarf) companion. Only one previously known white dwarf + brown dwarf binary is detected. This result is discussed in the context of the 2MASS detection limits, as well as other recent observational surveys that suggest a very low rate of formation (or survival) for binary stars with extreme mass ratios.

Additional Information

© 2007 The American Astronomical Society. Received 2007 February 2; accepted 2007 February 28. J. W. W. acknowledges financial support from a Harvey Mudd College National Merit Scholarship. M. G. acknowledges financial support from the Harvey S. Mudd Merit Award. Thanks to Tom Marsh (University of Warwick) for making his collection of WD finding charts available, and to Jessica Hall (University of Southern California) and Ryan Yamada (Harvey Mudd College) for their assistance in identifying white dwarfs. We also thank the anonymous referee for pointing out several papers that were helpful in improving the presentation of our results. This work was performed, in part, at the Jet Propulsion Laboratory (JPL), California Institute of Technology (CIT). Support for this work was provided by the National Aeronautics and Space Administration (NASA) under an Astrophysics Data Program grant issued through the Office of Space Science. This research made use of the NASA/Infrared Processing and Analysis Center (IPAC) Infrared Science Archive, which is operated by JPL/CIT, under contract with NASA, and data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and IPAC/CIT, funded by NASA and the National Science Foundation (NSF). We used the SIMBAD database, operated at CDS, Strasbourg, France, and NASA's Astrophysics Data System. The National Geographic Society-Palomar Observatory Sky Atlas (POSS-I) was made by CIT with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by CIT with funds from the NSF, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation.

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