Access Type

Open Access Dissertation

Date of Award

January 2025

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Physics and Astronomy

First Advisor

Renee R. Ludlam

Abstract

Neutron star low-mass X-ray binaries (NS LMXBs) provide crucial insights into the physics of accretion under extreme gravity. In this dissertation, we explore the capabilities of NuSTAR’s stray light (SL) observations to supplement, and in some cases, surpass focused data in spectral studies of bright LMXBs. Utilizing the use of SL datasets, we perform detailed spectral analyses of two Z sources: GX 340+0 and Sco X-1.

For GX 340+0, we compare 7 focused and 25 SL observations across multiple spectral states, demonstrating that SL data significantly expand temporal coverage and allow for the detection of long-term spectral evolution not evident in focused observations alone. Continuum modeling with double thermal components, along with relativistic reflection modeling using the {\sc relxillNS} framework, enables constraints on NS surface and disk temperatures, disk inclination and ionization.

For Sco X-1, we present the first spectral analysis using an intentional SL observation. The dataset captures the source in the flaring branch (FB) and it is modeled with thermal Comptonization. Reflection analysis shows a disk inclination consistent with previous X-ray and radio studies. This work validates the high precision spectra of intentional SL data and underscores its potential in extending exposure time for extremely bright sources limited by telemetry constraints in focused observations.

Together, these studies demonstrate that properly reduced NuSTAR SL observations offer a powerful tool for high-energy astrophysics. This dissertation establishes a framework for SL data analysis and highlights its value for future missions aiming to maximize science return without additional observing time.

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