The Runaway Binary LP 400-22 is Leaving the Galaxy
  We present optical spectroscopy, astrometry, radio, and X-ray observations of
the runaway binary LP 400-22. We refine the orbital parameters of the system
based on our new radial velocity observations. Our parallax data indicate that
LP 400-22 is significantly more distant (3 sigma lower limit of 840 pc) than
initially predicted. LP 400-22 has a tangential velocity in excess of 830 km/s;
it is unbound to the Galaxy. Our radio and X-ray observations fail to detect a
recycled millisecond pulsar companion, indicating that LP 400-22 is a double
white dwarf system. This essentially rules out a supernova runaway ejection
mechanism. Based on its orbit, a Galactic center origin is also unlikely.
However, its orbit intersects the locations of several globular clusters;
dynamical interactions between LP 400-22 and other binary stars or a central
black hole in a dense cluster could explain the origin of this unusual binary.
