Supersoft and quasisoft X-ray sources are collectively known as Very Soft X-ray Sources (VSSs) characterized by their considerably lower effective temperatures than normal X-ray emitting objects and the lack of significant emission above 1 keV, with measured temperatures ranging from about tens to less than about 300 eV, respectively. They are defined observationally and believed to be associated with a wide variety of astrophysical systems such as white dwarfs, neutron stars, and black holes. VSSs have been identified in our own Galaxy, the Magellanic Clouds, and other external galaxies. Due to the vicinity of the Magellanic Clouds and the low associated absorption of soft X-ray photons, they are unique in the studies of VSSs. However, no attempt has been made to search for VSSs and investigate the source population in the Magellanic Clouds using all the available archival data. A systematic survey of VSSs in the Magellanic Clouds was therefore performed using data from both XMM-Newton and Chandra. VSSs were identified by selection algorithim based on X-ray hardness ratio after the background galaxies and foreground stars were filtered. A total of 47 new supersoft and 75 new quasisoft candidates were identified. Six of them were strong enough for spectral analysis with derived temperatures of 15 – 250 eV and luminosities of of 3.5 ×?10?^34– 5.4 ×?10?^36 erg s^(-1). The softest and brightest candidate represents a promising supersoft candidate with a possible UV counterpart identified with XMM-Newton Optical Monitor having an estimated UV luminosity of ~2.7 ×?10?^35 erg s^(-1). The large dataset also allows the long-term studies of some of the previously identified supersoft X-ray sources. Through the comprehensive survey with multi-epoch data, an X-ray/UV stellar flare was discovered and its analysis is also reported. / published_or_final_version / Physics / Master / Master of Philosophy

Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2008/05/09). Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1974. / Typescript. Vita. Includes bibliographical references.

In this thesis the use of thin foil conical profile X-ray mirrors for high energy, large aperture, and lightweight telescopes is investigated. The telescope performance is studied using analytical solutions and ray tracing simulations. Expressions for the number of mirrors in a module, the collecting area, the efficiency of aperture utilisation, and the resolution are calculated for on-axis sources. For off-axis sources ray tracing is used and expressions to describe the performance are derived empirically. The sensitivity and effect of singly reflected rays on the image are also investigated, and the comparison is made with Wolter (I) profile optics. A technique for the production of super-smooth surfaces using a layer of acrylic lacquer is described. Several materials have been coated using this method to assess their suitability as potential mirror substrates. To quantitatively assess the quality of both substrate and lacquer finishes a program of X-ray scattering measurements has been carried out. Several different types of surfaces have been examined both before and after lacquer coating. Particular attention has been payed to the ability of the lacquer to remove surface features of different spatial wavelengths. An epoxy replicated test flat is also examined which provides an interesting comparison with the lacquer coating technique for the production of thin X-ray mirrors. As a consequence of the wide range of materials examined it has been possible to compare most of the different techniques for producing thin X-ray mirrors. There is no one solution for all applications and thin foil mirrors are indeed a competitive technology.

No description available.

The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, > 8m(2) effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e. g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.

Thesis. 1975. B.S. cn--Massachusetts Institute of Technology. Dept. of Physics. / MICROFICHE COPY AVAILABLE IN ARCHIVES. / Includes bibliographical references. / B.S.cn

Thesis (Ph.D)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (p. 201-206).

This thesis focuses on the radiation mechanisms of non-thermal X-rays and soft gamma-rays of two types of thousands year old spin-down powered pulsars. The thousands year old pulsars have distinct radiation behaviors from the middle-aged gamma-ray pulsars. In the magnetosphere of the pulsar, the particles are accelerated by the electric field resulting from the rotation of the neutron star. These accelerated particles move along the magnetic field lines and emit GeV gamma-ray curvature photons. For the middle-aged pulsars, most of the curvature photons, whose observed spectra are described well by power law with exponential cut-off, can escape out of the light cylinder. In X-ray band, the middle-aged pulsars usually have black body radiation with a weak non-thermal component described by power law. On the other hand, for the thousands-year-old pulsars, the curvature spectra in GeV band, which obey power law with exponential cut-off, are smeared out by the pair creation or missed by the line of sight. The secondary pairs generated by pair creation processes spiral around the magnetic field lines and emit synchrotron photons, and the young pulsars have stronger non-thermal X-ray and soft gamma-ray radiation than the middle-aged ones. Seven young pulsars have been studied here, they are the Crab pulsar, PSRs B0540-69, B1509-58, J1846-0258, J1811-1925, J1617-5055 and J1930+1852. These seven fall into two categories: the Crab-like pulsars and soft gamma-ray pulsars. The Crab-like pulsars include the Crab pulsar and the Giant Crab PSR B0540-69, and the soft gamma-ray pulsars include the other five. The main difference between the two types of young pulsars is that the Crab-like pulsars’ spectra peak at E ≤ 1MeV while the soft gamma-ray pulsars’ spectra (in units of MeV/cm2/s) peak at E ∼ 10MeV. Their spectra also have different photon indices in X-ray band. The physics behind is two different pair creations, the photon-photon pair creation and the magnetic pair creation. The former happens when a high energy photon collides with a soft photon, and the latter happens when a high energy photon penetrates through strong perpendicular magnetic field. In the outer gap of the pulsar, a large mount of pairs are generated around the null charge surface via photon-photon pair creation, and the electric field separates the two charges to move in opposite directions. Therefore, there are outflow and inflow of particles in the magnetosphere, whose curvature photons are converted to pairs by photon-photon pair creation and magnetic pair creation respectively. For the Crab-like pulsar, the non-thermal X-rays and soft gamma-rays are emitted by the outgoing secondary pairs generated by photon-photon pair creation in the outer magnetosphere; for the soft gamma-ray pulsar, the radiating secondary pairs are generated below the null charge surface by the magnetic pair creation. / published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Supernova explosions are among the most energetic events known in the universe, leaving supernova remnants (SNRs) as their relics. The cores of massive stars collapse to form neutron stars, among the most compact and strongest magnets in the cosmos. The thesis studies a sample of such magnetic "beauties" in X-rays, the magnetars and high-magnetic field pulsars (HBPs), with the motivation to understand their evolutionary links. We also address the connection between these sources by investigating their environs through their securely associated SNRs. Magnetars have ultra-high magnetic fields B ~ 10^{14} - 10^{15} Gauss (G) and include the soft-gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The HBPs have magnetic fields B ~ 10^{13} - 10^{14} G, intermediate between the classical rotation-powered pulsars (B ~ 10^{12} G) and magnetars. We focussed on two HBPs: J1119-6127 and J1846-0258, with similar spin-properties and associated with the SNRs G292.2-0.5 and Kes 75, respectively. In our studies, magnetar-like behavior was discovered from the Crab-like pulsar J1846-0258, clearly establishing a connection between the HBPs and magnetars for the first time, while no such behavior has been observed from PSR J1119-6127 so far. J1119-6127's overall X-ray properties together with its compact pulsar wind nebula resemble more the classical rotation-powered pulsars. We studied two magnetars, one from each sub-class: SGR 0501+4516 and AXP 1E 1841-045. The spectral and statistical analysis of the bursts and the persistent X-ray emission properties observed from them were found consistent with the magnetar model predictions as well as those seen in other SGRs. Finally, we probed the environment of these stellar magnets by performing a detailed X-ray imaging and spatially resolved spectroscopic study of two SNRs: G292.2-0.5 and Kes 73 associated with J1119-6127 and 1E 1841-045, respectively. We found that both SNRs point to very massive progenitors (>~25 solar masses), further supporting the growing evidence for magnetars originating from massive progenitors using other multiwavelength studies.