ORCID Identifier(s)

0000-0002-7352-7845

Graduation Semester and Year

2023

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics and Applied Physics

Department

Physics

First Advisor

Sangwook Park

Abstract

Understanding how exploding stars impact their surroundings is of fundamental importance to all areas of astrophysics. Young supernovae (SNe) and their remnants open a window into directly studying the composition and distribution of the fresh products of nucleosynthesis. They also are instrumental in probing the ambient circumstellar medium (CSM), revealing the late-stage evolution of massive stars that culminates in a cataclysmic explosion. My thesis is divided into understanding the evolution of two core-collapse SNe: SN 1987A and SN 2021krf. Supernova (SN) 1987A is the closest observed SN (about 51 kpc) in the last 400 years and offers a unique opportunity to understand the makings of a supernova remnant (SNR) from a core-collapse supernova (CCSN). Based on observations with the Chandra X-ray Observatory, we present the latest spectral and photometric evolution of the X-ray remnant of SN 1987A (SNR 1987A). With high-resolution Chandra HETG spectral modeling, we find an increase in electron temperatures (by about 40 %) and decreasing volume emission measures between 2011 and 2018 which suggest that the shocks moving through the inner ring have started interacting with less dense CSM, probably beyond the inner ring. The soft (0.5-2.0 keV) X-ray light curve shows a linearly declining trend (by about 18 %) between 2016 and 2020 as the blast wave heats the low-density CSM from the red supergiant phase of SN 1987A’s progenitor. The Chandra ACIS X-ray spectra of SNR 1987A since 2018 show the emerging presence of the Fe K line suggesting an increasing contribution from the reverse shocked layers of the SN ejecta. The morphological evolution and changes in the expansion rate of SNR 1987A are also consistent with these physical interpretations. We also present the near-infrared (NIR) and optical observations of the recent Type Ic supernova (SN Ic) SN 2021krf performed between days 13 and 259 since the explosion with several ground-based telescopes. The NIR spectrum at day 68 exhibits a rising K-band continuum flux density longward of about 2.0 microns indicating the presence of dust, likely formed in the SN ejecta. At late times (70–300 days), we find that the optical light curves of SN 2021krf decline substantially more slowly than that expected from 56-Co radioactive decay. We reproduced the entire bolometric light curve with a combination of radioactive decay and an additional powering source in the form of a central engine of a millisecond pulsar with a magnetic field of typical radio pulsars.

Keywords

Supernovae, Supernova remnants

Disciplines

Physical Sciences and Mathematics | Physics

Comments

Degree granted by The University of Texas at Arlington

Available for download on Thursday, August 01, 2024

Included in

Physics Commons

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