A DECADE-BASELINE STUDY OF THE PLASMA STATES OF EJECTA KNOTS IN CASSIOPEIA A

We present the analysis of 21 bright X-ray knots in the Cassiopeia A supernova remnant from observations spanning 10 yr. We performed a comprehensive set of measurements to reveal the kinematic and thermal state of the plasma in each knot, using a combined analysis of two high energy resolution High Energy Transmission Grating (HETG) and four medium energy resolution Advanced CCD Imaging Spectrometer (ACIS) sets of spectra. The ACIS electron temperature estimates agree with the HETG-derived values for approximately half of the knots studied, yielding one of the first comparisons between high resolution temperature estimates and ACIS-derived temperatures. We did not observe the expected spectral evolution—predicted from the ionization age and density estimates for each knot—in all but three of the knots studied. The incompatibility of these measurements with our assumptions has led us to propose a dissociated ejecta model, with the metals unmixed inside the knots, which could place strong constraints on supernova mixing models.United States. National Aeronautics and Space Administration (Award NNX10AE25G)National Science Foundation (U.S.) (Partnerships in Astronomy & Astrophysics Research and Education Grant AST-0849736)United States. National Aeronautics and Space Administration (Earth and Space Science Fellowship)United States. National Aeronautics and Space Administration (Harriet Jenkins Predoctoral Fellowship Program)Vanderbilt University (Provost Graduate Fellowship

High-resolution studies of charge exchange in supernova remnants with Magellan, XMM-Newton, and Micro-X

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.120Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 239-249).Charge exchange, the semi-resonant transfer of an electron from a neutral atom to an excited state in an energetic ion, can occur in plasmas where energetic ions are incident on a cold, at least partially neutral gas. Supernova remnants, especially in the immediate shock region, provide conditions conducive to charge exchange. The emission from post charge-exchange ions as the captured electron cascades down to the ground state, can shed light on the physical conditions of the shock and the immediate post-shock material, providing an important tool for understanding supernova explosions and their aftermath. In the first half of this thesis, I study charge exchange in the galactic supernova remnant G296.1-0.5 in two energy bands: the optical and the X-ray. The optical study, performed using both imaging and high resolution spectroscopy from the IMACS instrument on the Magellan Baade Telescope at Las Campanas Observatory, seeks to identify 'Balmer-dominated shocks' in the remnant, which signal the occurrence of charge exchange between hot, postshock protons and colder neutral hydrogen in the environment. The X-ray study probes line ratios in dispersed spectral data obtained with XMM-Newton RGS from an X-ray lobe in the NW of the remnant to hunt for signatures of charge exchange. The dispersed data are degraded by the extended nature of the source, blurring emission lines and making precise measurements difficult. The focus of the second half of this thesis is Micro-X : a sounding rocket-borne X-ray telescope, utilizing an array of microcalorimeters to achieve high energy resolution for even extended sources. I describe the design and commissioning of the payload and the steps toward launch, which is anticipated in the spring of 2015.by Sarah Nicole Trowbridge Heine.Ph. D