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Exploring the Mass Accretion Rates of Neutron Star X-Ray Binaries and the Properties of Cadmium Zinc Telluride for Hard X-Ray Astronomy


Pike, Sean Nicholas (2023) Exploring the Mass Accretion Rates of Neutron Star X-Ray Binaries and the Properties of Cadmium Zinc Telluride for Hard X-Ray Astronomy. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ctjf-2768.


My thesis work has consisted of investigations of several X-ray binaries using the Nuclear Spectroscopic Telescope Array (NuSTAR), as well as characterization of NuSTAR-like hybrid X-ray detectors for the purpose of future hard X-ray obser- vatories. I present analyses of three X-ray binaries in particular, probing different luminosities with the goal of investigating accreting neutron stars at different ac- cretion rates. At high accretion rates, approaching and moderately exceeding the Eddington limit, I performed a timing and spectral analysis of the neutron star su- pergiant X-ray binary SMC X-1. I tracked the transient pulsations of this source at different apparent luminiosities and analyzed the source spectrum as pulsations evolved in order to infer that the mechanism leading to pulsation transience is likely related to periodic obscuration by a warped accretion disk. At lower accretion rates, I studied the low-mass X-ray binary GRS 1741.9–2853. I proposed for NuSTAR observations of this source in outburst, and as a result I observed two type-I X- ray bursts originating from the source. I performed a time-resolved spectroscopic study of each of these bursts, and I used the results of this analysis to determine the composition of the burning material and the distance to the source from Earth. The third X-ray binary I present is MAXI J1848–015. This source was discovered by the Monitor of All-sky X-ray Image (MAXI) in winter 2020 at which point its luminosity was abnormally low for an accreting compact object in outburst, making it a good candidate for the study of neutron star X-ray binaries at low accretion rates. I performed rapid follow-up of the source with NuSTAR, and I performed a detailed spectroscopic study of the NuSTAR observations, utilizing relativistic disk reflec- tion models in order to determine that the source is in fact a black hole rather than a neutron star. Complementing these observational astrophysics projects, I character- ized Cadmium Zinc Telluride (CZT) detectors procured from Redlen Technologies in order to determine their usefulness for future hard X-ray observatories. Using Python, I produced an adaptable calibration and analysis pipeline with which to analyze noise, leakage current, spectral, and other data which I obtained in the lab. Using this pipeline, I determined that the material available from Redlen shows good uniformity, yield, and superior spectral resolution up to high photon energies, making it an excellent candidate for application to hard X-ray astronomy.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:X-ray astronomy; neutron stars; black holes; accretion; cadmium zinc Telluride; relativity; pulsars; type-I X-ray bursts; X-ray binaries; X-ray detectors
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Harrison, Fiona A.
Thesis Committee:
  • Weinstein, Alan Jay (chair)
  • Hopkins, Philip F.
  • Martin, D. Christopher
  • Harrison, Fiona A.
Defense Date:18 July 2022
Non-Caltech Author Email:seannpike (AT)
Funding AgencyGrant Number
Record Number:CaltechTHESIS:07262022-180810750
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 5 adapted for Chapter 4 adapted for Chapter 3
Pike, Sean Nicholas0000-0002-8403-0041
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14988
Deposited By: Sean Pike
Deposited On:01 Aug 2022 17:50
Last Modified:20 Jun 2023 23:09

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