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F. M. Walter (SUNY Stony Brook)
HST WFPC2 obervations over a 3 year baseline have yielded the proper motion and parallax of the isolated neutron star RX~J185635-3754. It is the closest known neutron star, at a distance of 62~pc. The projected proper motion of 85~km~s-1 places the neutron star in the vicinity of the Upper Scorpius OB association, and in close proximity to the runaway O star \zeta~Oph, about 1.1 million years ago.
I will discuss implications for the radius of the neutron star. The likely age of this neutron star yields a clean point on the cooling curve. On the assumption that RX~J185635-3754 was the binary companion to \zeta~Oph, the kick velocity imparted at birth must have been about 200~km~s-1.
This research is supported by STScI.
The author(s) of this abstract have provided an email address for comments about the abstract: fwalter@astro.sunysb.edu