ORCID Identifier(s)

0000-0002-9312-7937

Graduation Semester and Year

2018

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics and Applied Physics

Department

Physics

First Advisor

Sangwook Park

Abstract

In this thesis, we describe our detailed analysis of the core-collapse supernova remnant (CCSNR) G292.0+1.8 (G292 hereafter) using data collected by NASA's Chandra X-ray Observatory (Chandra). In the first part of this thesis, we use data collected by Chandra's grating spectrometer to study the motion of the SNR's ejecta. We study this motion by measuring Doppler shifts of atomic spectral emission lines. We measure the radial velocities (vr) of 33 emission features in the remnant. We find that the ejecta have high vr (-2300 ≲ vr ≲ 1400 km s-1). We also find that most of the ejecta are moving towards us (17 of the 24 ejecta knots have negative or blueshifted vr). This asymmetry in the kinematic structure of the ejecta gas may have originated from an asymmetric SN explosion. Based on our measured vr-distribution, we qualitatively locate the positions of the reverse shock (RS) and contact discontinuity (CD). We analyze the dynamics of the remnant using theoretical models, and estimate a total ejecta mass of ≲8 M☉. Considering the previously estimated mass of the circumstellar medium (CSM), we place an upper limit of ≲35 M☉ on the mass of the G292 progenitor star. In the second part of this thesis, we analyze the chemical composition and physical properties of G292 in detail. We use data from a long exposure (~530 ks) of G292 collected using Chandra's ACIS-I detector. We use our adaptive mesh method to divide the remnant into 2147 smaller rectangular regions. We analyze the emission from each of these regions by extracting spectra, and fitting these spectra with a model appropriate for shocked, hot ionized SNR gas. Based on our model fits we identify ~1400 ejecta-dominated regions and ~700 CSM-dominated regions. The spatial distribution of the CSM-dominated regions reveals the structure and morphology of the shock-heated CSM in G292. We create maps revealing the detailed spatial distribution of the abundances of O, Ne, Mg, Si, S and Fe, the absorbing column (NH), and the plasma physical parameters: electron temperature (kT), ionization timescale (net), and the electron density (ne), and thermal pressure (P). For the first time, we detect and localize the Fe-rich ejecta in G292 using Chandra data. We find that the O-, Ne-, Mg-rich ejecta are preferentially expelled in the NW-SE direction. On the other hand, the heavier inner ejecta, represented by the elements Si, S and Fe, are almost exclusively found in the northwestern hemisphere with hardly any in the southeast. This suggests that the heavier ejecta in G292 were expelled in the opposite direction to which the associated pulsar (PSR J1124-5916) was presumably kicked. We provide the first observational evidence that Fe, a key explosive nucleosynthesis product, was ejected opposite to the neutron star in G292. Also, for the first time in X-rays, we identify the northern component of the equatorial ring, a dense, bright, ring-like CSM structure that runs east-west along the remnant's "equator." From our analysis of the dynamics of the remnant, our measured elemental abundance ratios, and calculated masses of the ejecta and CSM, we estimate a G292 progenitor mass of 13-30 M☉.

Keywords

Supernova, Supernova remnant, Oxygen-rich, Kinematics, Ejecta, Circumstellar medium, Circumstellar ring, Reverse shock, Contact discontinuity, Progenitor mass, Mapping, Iron, Nucleosynthesis, Asymmetry, Neutron star, Pulsar, X-ray, Chandra, HETG

Disciplines

Physical Sciences and Mathematics | Physics

Comments

Degree granted by The University of Texas at Arlington

Included in

Physics Commons

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