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 Physics , 2010, DOI: 10.1088/0004-637X/724/1/669 Abstract: We have redetermined the parallax and proper motion of the nearby isolated neutron star RX~J185635-3754. We used eight observations with the high resolution camera of the HST/ACS taken from 2002 through 2004. We performed the astrometric fitting using five independent methods, all of which yielded consistent results. The mean estimate of the distance is 123 (+11, -15) pc (1 sigma), in good agreement with our earlier published determination.
 Physics , 2002, DOI: 10.1086/343850 Abstract: New astrometric analysis of four WFPC2 images of the isolated neutron star RX J185635-3754 show that its distance is 117 +/- 12 pc, nearly double the originally published distance. At the revised distance, the star's age is 5 x 10^5 years, its space velocity is about 185 km/s, and its radiation radius inferred from thermal emission is approximately 15 km, in the range of many equations of state both with and without exotic matter. These measurements remove observational support for an extremely soft equation of state. The star's birthplace is still likely to be in the Upper Sco association, but a connection with zeta Oph is now unlikely.
 Physics , 2003, DOI: 10.1086/378089 Abstract: The Vela pulsar is the brightest pulsar at radio wavelengths. It was the object that told us (via its glitching) that pulsars were solid rotating bodies not oscillating ones. Along with the Crab pulsar is it the source of many of the models of pulsar behavior. Therefore it is of vital importance to know how far away it is, and its origin. The proper motion and parallax for the Vela pulsar have been derived from 2.3 and 8.4 GHz Very Long Baseline Interferometry (VLBI) observations. The data spans 6.8 years and consists of eleven epochs. We find a proper motion of $\mu_{\alpha {\rm cos}\delta}= -49.61 \pm 0.06, \mu_\delta= 29.8 \pm 0.1$ \myr and a parallax of $3.4 \pm 0.2$ mas, which is equivalent to a distance of $293_{-17}^{+19}$ pc. When we subtract out the galactic rotation and solar peculiar velocity we find $\mu_* = 45 \pm 1.3$ \myr with a position angle (PA) of $301^\circ\pm1.8$ which implies that the proper motion has a small but significant offset from the X-ray nebula's symmetry axis.