Disk and halo wide binaries from the Revised Luyten Catalog: probes of star formation and MACHO dark matter

Preprint
Publisher Website
Google Scholar
  • 28 July 2003
Abstract
We present a catalog of 1147 candidate common proper motion binaries selected from the revised New Luyten Two-Tenths Catalog. Among these, we then identify 984 genuine physical pairs using the measured proper-motion difference and the relative positions of each binary's components on a reduced proper-motion (RPM) diagram. The RPM positions also serve to classify them as either disk main-sequence (799), halo subdwarf (110), or pairs containing at least one white dwarf (75). The disk and halo samples are complete to separations of \theta=500" and \theta=900", which correspond to ~0.1 pc and ~1 pc, respectively. At wide separations, both distributions are well described by single power laws, dN/d\theta ~ \theta^{-\alpha}: \alpha=1.72+-0.07 for the disk and \alpha=1.53+-0.10 for the halo. The fact that these distributions have similar slopes (and similar normalizations as well) argues for similarity of the star-formation conditions of these two populations. The fact that the halo binaries obey a single power law out to ~1 pc permits strong constraints on halo dark-matter candidates. At somewhat closer separations (10"<\theta<25"), the disk distribution shows a pronounced flattening, which is detected at very high statistical significance and is not due to any obvious systematic effect. We also present a list of 11 previously unknown halo stars with parallaxes that are recognized here as companions of Hipparcos stars.

This publication has 0 references indexed in Scilit: