Measuring the Spin-down of Two Nearby Isolated Neutron Stars

The nearest thermally emitting neutron stars arguably offer the best prospectsfor measuring neutron star radii, but this task is complicated by our lack ofknowledge about their magnetic field strengths, which hinders modeling of theirspectra. Recently, we have determined field strengths for two objects usingdedicated Xray timing observations: by measuring spindown and assuming adipole field, we find magnetic fields between normal pulsars and magnetars. Wepropose to complete this sample with timing observations of the two remainingobjects in this class with clear periodicities: RX J0420.05022 and RXJ0806.44123. This will provide vital, modelindependent constraints to aid ininterpreting the mysterious absorption features found in their Xray spectra. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]