Abstract

Observations of the millisecond pulsar J1614-2230 as part of the NANOGrav 12.5 yr dataset were utilised to study the scintillation and interstellar medium along the line of sight of PSR J1614-2230. Modelling noise signals in pulsar line of sight allows for isolation of the raw signal and therefore more precise pulse period measurements. These are extremely useful in Pulsar Timing Arrays and in their potential to be used as cosmic detectors for the gravitational wave background. J1614 presented clear, distinguishable intensity variations in a long observation taken in March 2014 by B.J.Shapiro-Albert et al. (2020), which provided motivation to further probe NANOGrav’s 12.5 yr observations of the pulsar. Dynamic spectra were constructed for each observation, from which the 2D Auto correlation function and consequently, the scintillation parameters, were calculated. Scintillation parameters consist of three variables describing the characteristic nature of the average scintle in a dynamic spectrum: the width, height and rotation. The construction of time series of these parameters allowed for probing of trends across the 12.5 yr observations. Sinusoidal curve fitting was reasonably successful for one of these parameters while the other two need to be revisited with more data points and more precise constraints on the 2D ACF. For the width variation, although a sinusoidal fit was unsuccessful, a tentative model to explain the observed trend is proposed. The scintillation parameters are also tied to descriptions of the scattering medium, namely the strength of the scattering medium, the mean-square scattering angle per unit length and the refractive angle. Values of each of these were calculated using the thin screen model, derived in J.M.Cordes & B.J.Rickett (1998). Known measurements (S.K.Ocker et al. (2020)) of the H II region eclipsing the pulsar (Sh 2-7) were also used in approximating these values. Information about the refractive angle was further used to estimate a scale for the pulse delay caused by refraction, which will be essential in pinpointing delays due to the gravitational wave background, a main goal of NANOGrav.

Library of Congress Subject Headings

Pulsars--Observations; Radio waves--Scintillation; Interstellar matter

Publication Date

4-2023

Document Type

Thesis

Student Type

Graduate

Degree Name

Physics (MS)

Department, Program, or Center

School of Physics and Astronomy (COS)

Advisor

George Thurston

Advisor/Committee Member

Michael Richmond

Advisor/Committee Member

Scott Franklin

Campus

RIT – Main Campus

Plan Codes

PHYS-MS

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