Dissertation

On July 8, 2004 I successfully defended my dissertation entitled "Gravitational Wave Astronomy Using Spaceborne Detectors." My Ph.D. advisor was Dr. Neil Cornish.

At the moment only a portion of the original research material presented in my dissertation has been published in journal articles,

  1. Characterizing the Galactic Gravitational Wave Background with LISA, S. E. Timpano, L. J. Rubbo, and N. J. Cornish, Physical Review D 73, 122001 (2006) [gr-qc/0504071]

  2. Forward Modeling of Space-borne Gravitational Wave Detectors, L. J. Rubbo, N. J. Cornish, and O. Poujade, Physical Review D 69, 082003 (2004). [gr-qc/0311069]

  3. LISA Response Function, N. J. Cornish and L. J. Rubbo, Physical Review D 67, 022001 (2003). [gr-qc/0209011]

The rest will eventually be published in future papers. Since not all of my work is available in the journals yet, I've decided to make my dissertation available for anyone interested in reading it. Below is the abstract for my dissertation followed by links for downloading the full work. I've also included the original defense talk for viewing.

Abstract

This dissertation explores the use of spaceborne gravitational wave detectors as observatories for studying sources of gravitational radiation. The next decade will see the launch of the first space-based gravitational wave detector. Planning for several follow on missions is already underway. Before these observatories are constructed, extensive studies into their responses, expected output, and data analysis techniques must be completed. In this dissertation these issues are addressed using the proposed Laser Interferometer Space Antenna (LISA) as an exemplary model.

The first original work presented here is a complete description of the response of a spaceborne detector to arbitrary gravitational wave signals. Previous analyses worked either in the static or low frequency limits. Part of this investigation is a coordinate free derivation of the response of a general detector valid for all frequencies and for arbitrary motion. Following directly from this result is The LISA Simulator, a virtual model of the LISA detector, in addition to an adiabatic approximation that extends the low frequency limit by two decades in the frequency domain.

Unlike most electromagnetic telescopes, gravitational wave observatories do not return an image of a particular source. Instead they return a set of time series. Encoded within these time series are all of the sources whose gravitational radiation passes through the detector during its observational run. The second original work presented here is the extraction of multiple monochromatic, binary sources using data from multiple time series. For binaries isolated in frequency space and with a large signal to noise ratio, it is shown that these sources can be removed to a level that is below the local effective noise.

A concern for the LISA mission is the large number of gravitational wave sources located within the Milky Way galaxy. The superposition of these sources will form a confusion limited background in the output of the detector. The final original work reported here is a Monte Carlo simulation of the galactic gravitational wave background as it will be observed by LISA. Using this simulation a number of characteristics of the background are calculated, including estimates of the number and type of sources LISA will be able to identify, and the average distance in frequency space between bright sources. Also given is a demonstration of how a standard Gaussian test can be used to distinguish the galactic background from the intrinsic detector noise.

The complete dissertation is available here as a pdf document (1.5MB).

Slides from my defense talk are found here as a pdf document (1.1MB).

For those Montana State graduate students beginning the long road of writing their dissertation, I've gathered up the LaTeX template files used to format my dissertation. These files are available here (60KB).