Doctor of Philosophy (PhD)
Physics & Astronomy
The Kepler mission has been the catalyst for discovery of nearly 5,000 confirmed and candidate exoplanets. The majority of these candidates orbit Sun-like stars, and have orbital periods comparable to or shorter than that of the Earth, due to the selection bias inherent in the transit method and the limitations of automated transit search algorithms. We aim to develop a richer understanding of the population of exoplanets around the lowest-mass stars, the M spectral type. We are particularly interested in exoplanets with long orbital periods, which are difficult or impossible to find using standard transit search algorithms. In our study, we develop a unique methodology using the novel Planet Hunters citizen science project in conjunction with a new searching/scoring pipeline, SATCHEL, constructed from scratch to handle crowd-sourced time-series photometry.
With the results from SATCHEL, we perform a rigorous completeness and reliability study to estimate the true number of planets orbiting our sample of 3,262 M-dwarf stars. After correcting for the geometric transit probability and the window function of the Kepler mission, we calculate occurrence rates for planets with radii 2 - 43 R⊕ and orbital periods 1 - 10,000 days, obtaining a total rate of about 10.0 ±
5.11 planets per M-dwarf star. The vast majority of these planets likely lie in bins of small radius and long periods, implying highly efficient planet formation out to at least 5 AU from the host star. For planets with periods 1 - 1,000 days, our results of 1.77 ± 0.55 planets per M-dwarf are in good agreement with contemporary values, and qualitative agreement with predictions from other detection methods.
Safron, Emily Jane, "Are Long-Period Exoplants Around Cool Stars More Common Than We Thought?" (2022). LSU Doctoral Dissertations. 5785.