We have recently measured the angle between the spin and orbital angular momenta of PSR B1534+12 to be either 25 ± 4 or 155 ± 4. This misalignment was almost certainly caused by an asymmetry in the supernova explosion that formed its companion neutron star. Here we combine the misalignment measurement with measurements of the pulsar and companion masses, the orbital elements, proper motion, and...

The evolution leading to the formation of a neutron star in the very young Westerlund 1 star cluster is investigated. The turnoff mass has been estimated to be ∼ 35 M⊙, indicating a cluster age ∼ 3 − 5 Myr. The brightest X-ray source in the cluster, CXO J164710.2-455216, is a slowly spinning (10 s) single neutron star and potentially a magnetar. Since this source was argued to be a member of th...

We have observed the persistent but optically unidentified X-ray source X1908+075 with the PCA and HEXTE instruments on RXTE. The binary nature of this source was established by Wen, Remillard, & Bradt (2000) who found a 4.4-day orbital period in results from the RXTE ASM. We report the discovery of 605 s pulsations in the X-ray flux. The Doppler delay curve is measured and provides a mass func...

The typical product of the star formation process is a multiple star system, most commonly a binary star. Binaries have provided the first dynamical measures of the masses of pre-main-sequence (PMS) stars. These measurements have established that T Tauri-like stars are indeed of solar mass or less, and have provided preliminary support for the mass calibrations of theoretical PMS evolutionary t...

Recent observations of pre-main sequence stars suggest that all stars may form in multiple systems. However, in the Galactic field only about 50 per cent of all systems are binary stars. We investigate the hypothesis that stars form in aggregates of binary systems and that the dynamical evolution of these aggregates leads to the observed properties of binary stars in the Galactic field. A thoro...

We present a high spatial resolution multi-wavelength survey of 44 young binary star systems in Taurus-Auriga with separations of 10 1000 AU. These observations, which were obtained using the Hubble Space Telescope and the NASA Infrared Telescope Facility, quadruple the number of close (< 100 AU) binary stars with spatially resolved measurements from 0.3 to 2.2 μm and are the first 3.6 μmmeasur...