X-ray and optical emission from neutron stars and pulsar wind nebulae

This dissertation is devoted to X-ray and optical-UV observations of Neutron Stars (NSs) and Pulsar-Wind nebulae (PWNe). I begin with Introduction (Chapter 1) where I briefly review the astrophysics of pulsars, their winds and synchrotron radiation. I also present an overview of the results of previous X-ray and optical observations of pulsars and PWNe which are relevant to the content of the dissertation. To provide a broader (and more complete) view of the NS population, I then describe observational properties of its more exotic representatives (e.g., Anomalous X-ray Pulsars and Central Compact Objects in Supernova Remnants), many of which have emerged only recently.;Part I of the dissertation describes the UV and X-ray observations of the famous Vela pulsar and its spectacular PWN (Chapter 2). The observations which I analyzed were carried out with the Chandra X-ray Observatory and Hubble Space Telescope. I begin by presenting the spectrum and lightcurves of the pulsar as they are seen in different bands of electromagnetic radiation. I then turn to imaging observations of the Vela PWN. Thirteen observations of the Vela PWN with Chandra, spanning a period of 3 years, reveal its complex and variable structure which consists of arcs, jets, knots and diffuse emission. Especially interesting is the long external jet which changes its shape on a timescale of weeks and contains blobs moving at speeds of (0.5-0.6)c. In addition to the fine structure of the inner PWN, a much larger and fainter asymmetric X-ray nebula emerges in the deep summed images. The shape of this outer PWN is similar to that of the radio PWN. I also present the high-resolution spectral map of the Vela PWN and compare its X-ray properties with those of other PWNe.;To see if other PWNe are alike and to study the connection between the pulsar and the PWN properties, I retrieved data on rotation-powered pulsars and PWNe from the Chandra archive. Using these data, I performed a uniform statistical analysis of the PSR/PWN X-ray properties. The results, which potentially provide powerful diagnostic of the energetics and emission mechanisms of neutron stars, are presented in Chapter 3.;Part II focuses on the individual observations of two middle-aged pulsars (Gemiga and B0656+14; Chapters 4 and 5), very old millisecond pulsar J0437--4715 (Chapter 6), and the enigmatic central source in the Supernova Remnant G266.2--1.2 (Chapter 7). The observations were carried out with HST and Chandra. For each of these objects, I describe the observation setups, data reduction, quantitative results (e.g., fluxes, spectra, light curves) and their astrophysical implications (e.g., origin of the observed radiation, NS surface temperature, connection between the X-ray and optical radiation).