2026-09-23T04:27:43Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/45397 2023-07-11 col_2142_5131 col_2142_8859 com_2142_5130 com_2142_8858 com_2142_234

Lamb, Frederick K. Stack, John D. Lamb, Frederick K. Fields, Brian D. Thaler, Jonathan J. Lo, Ka-Ho 2013-08-22T16:38:59Z 2013-08-22T16:38:59Z 2013-08 2013-08-22T16:38:59Z 2013-08 "Analysis of observations of the X-ray emission produced by accreting neutron stars with millisecond spin periods can provide important information about the masses M and radii R of neutron stars, thereby yielding uniquely valuable information about the still uncertain properties of cold matter at several times the density of nuclear matter; about the evolution of neutron star magnetic fields and spin rates; and about the physics of accretion onto these stars, which are found in close, low-mass binary star systems. Avenues for obtaining this information include modeling the accretion- and nuclear-powered millisecond X-ray brightness oscillations produced by some of these stars and the spectra of their nuclear-powered emission, and then comparing these models with high-quality X-ray data. In this thesis, I explore the so-called ""nearly aligned moving spot model"" that has been proposed to explain many of the observed properties of the accretion-powered millisecond X-ray brightness oscillations produced by some accreting neutron stars in close, low-mass binary star systems and compare the properties this model predicts with the observed properties of these stars. I also study the accuracy and precision with which M and R can be determined by analyzing energy-resolved waveforms of the X-ray brightness oscillations seen during some of the thermonuclear X-ray bursts produced by some of these neutron stars. Finally, I describe how comparison of high-precision measurements of X-ray burst spectra with the spectra predicted by high-precision model atmosphere calculations can be used to constrain M and R. I find that many observed properties of the accretion-powered millisecond X-ray oscillations can be successfully explained by a model in which the X-ray emitting areas on the neutron star surface are close to the star's rotation pole but wander. I find that M and R can be tightly constrained by analyzing energy-resolved X-ray burst oscillation waveform data measured by a future X-ray satellite instrument having 2-30 keV energy coverage and an effective area of 10 m^2, such as the proposed LOFT or AXTAR missions, provided the hot spots that produce these oscillations are not too far from the star's rotation equator. The precision of these M and R measurements can be increased substantially by independent knowledge of the inclination and other properties of the system. Finally, I find that the detailed model atmosphere spectra computed by Suleimanov et al. (2012) provide excellent descriptions of the most precise spectra of X-ray bursts that are currently available, verifying these models and potentially allowing M and R to be constrained using them. I explain the methodology used, describe the results, and discuss their implications." Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2013-05-08T14:40:26Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 1 Lo_Ka-Ho.pdf: 2324958 bytes, checksum: 78879743842ba7083cf8def153707c87 (MD5) Made available in DSpace on 2013-08-22T16:38:59Z (GMT). No. of bitstreams: 2 Ka-Ho_Lo.pdf: 2324958 bytes, checksum: 78879743842ba7083cf8def153707c87 (MD5) license.txt: 4057 bytes, checksum: 82a37a06e17e89957272cc4d8df774df (MD5) http://hdl.handle.net/2142/45397 en Copyright 2013 Ka-Ho Lo neutron stars dense matter equation of state bursts millisecond pulsars Large Observatory for X-ray Timing (LOFT) Accretion- and nuclear-powered phenomena in neutron stars with millisecond spin periods text Physics 1244 Physics 0240 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Physics -UIUC 10KS0240PHD