Observational and Theoretical Studies of Radio Technosignatures and Pulsars

Open Access
- Author:
- Sheikh, Sofia
- Graduate Program:
- Astronomy and Astrophysics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 02, 2021
- Committee Members:
- Rebekah Dawson, Major Field Member
Steinn Sigurdsson, Major Field Member
Jason Wright, Chair & Dissertation Advisor
Randall Mcentaffer, Program Head/Chair
Sarah Shandera, Outside Unit & Field Member
Jill Tarter, Special Member - Keywords:
- Technosignatures
Astrobiology
Radio Astronomy
Pulsars
SETI
Astrostatistics
Astronomy
Nulling Pulsars
Drift Rates
Extraterrestrial Intelligence - Abstract:
- A "technosignature" has been defined as an "object, substance, and/or pattern whose origin specifically requires a [technological] agent," by analogy with biosignatures. While searches for radio technosignatures from extraterrestrial intelligence (ETI) are still the most developed, recent advances in exoplanet astronomy and computation have catalyzed a new era of technosignature searches beyond the radio wavelengths. To begin, I explore this new, expanded technosignature paradigm by proposing the first non-tautological definition of a technosignature. I then provide a framework for comparing disparate search strategies - across wavelengths, sub-disciplines, and methodologies - via the Nine Axes of Merit for Technosignature Searches. I will show that radio technosignature theory must be further developed as well; previous searches for radio technosignatures had used a maximum drift rate of approximately 1 Hz/s at 1 GHz, but I find that a limit 200 times larger is necessary to account for potential acceleration from known exoplanetary systems. I perform a full narrowband radio technosignature search of the Earth Transit Zone (ETZ), an area of the sky with a favourable geometry for ETI observers of the solar system, and set new upper limits on the occurrence rate and power of radio transmitters in the ETZ. I then discuss how pulsars, as galactic radio sources with an entangled technosignature history, can help us understand more about what is "natural" and what is "artificial" in the radio sky, and statistically investigate pulsar nulling behaviour for more pulsars and parameters than in the previous literature. Finally, I investigate a radio signal-of-interest detected in observations of Proxima Centauri and use it as a case study to develop a "checklist" of signal verification tests that should be performed on future signals-of-interest.