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J.A. Tomsick, A. Quirrenbach, S. Frink (University of California, San Diego)
We will perform narrow-angle observations of several X-ray binaries to determine their orbits, and we will observe ~50 X-ray binary systems in wide-angle mode to measure their distances and proper motions. Sources with mass estimates for the compact component of > 3\,M\odot are generally called ``black hole candidates'', since this mass is above the theoretical neutron star limit. Narrow-angle observations of these sources provide a direct test of the dynamical mass estimates on which the black-hole evidence is based. Better measurements of the black-hole masses will provide constraints on possible evolutionary paths that lead to the black-hole formation. When combined with X-ray data, mass measurements may provide additional constraints on the black-hole spin. Precise mass determinations of neutron star systems can address the question of whether neutron stars can be significantly more massive than 1.4\,M\odot, which would eliminate soft models of the neutron star equations of state. The wide-angle observations will probe the Galactic distribution of X-ray binaries through parallaxes and proper motions. They will also eliminate the uncertainties in the luminosities of individual sources, which is currently up to a full order of magnitude. This will enable more detailed comparisons of X-ray observations to physical models such as advection-dominated accretion flows (ADAFs). We intend to carry out the following measurements: \begin{itemize} \item{Determine the orbits of two black-hole candidates to measure the black hole masses.} \item{Obtain precise mass measurements for two neutron star systems to constrain neutron star equations of state.} \item{Determine the distances and thus luminosities of selected representatives of various classes of X-ray binaries (black-hole candidates, neutron stars, jet sources, ADAF sources).} \item{The same observations will also yield proper motions, from which the age of the population can be estimated.} \end{itemize}
The author(s) of this abstract have provided an email address for comments about the abstract: jtomsick@ucsd.edu