Searching for Stellar Cycles using Changes in Flare Rates
Research Mentor(s)
Davenport, James R. A., 1983-
Description
The 11-year Solar Cycle is a property of the Sun's magnetic field. At the beginning of a cycle, the magnetic field is turbulent and flare rates are at their highest. Halfway through the cycle, the magnetic reaches its calmest point, and we see less activity. We use the relationship between flare rates and a star's point in the cycle to search for stellar cycles in distant stars. Kepler provides 4-year periods of observations for a large batch of stars. We examine the active stars, which are pulled from the Kepler data by Davenport (2016). For each active star, we determine a time vs flare-frequency plot. Using the Bayesian Information Criterion (BIC), we find a best fit polynomial for the plot. This BIC prevents over-fitting of the data by weighing the chi-squared vs the degree, heavily penalizing higher degree polynomials. A fit of degree 1 or higher highlights a trend in the frequency over time, meaning it's likely that the observed star has a stellar cycle. Understanding how common these cycles are, and how long each cycle lasts, will give insight into the magnetic fields of stars.
Document Type
Event
Start Date
16-5-2018 9:00 AM
End Date
16-5-2018 12:00 PM
Department
Physics/Astronomy
Genre/Form
student projects, posters
Subjects – Topical (LCSH)
Solar activity; Stellar activity; Solar cycle; Sunspots; Solar magnetic fields
Type
Image
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.
Language
English
Format
application/pdf
Searching for Stellar Cycles using Changes in Flare Rates
The 11-year Solar Cycle is a property of the Sun's magnetic field. At the beginning of a cycle, the magnetic field is turbulent and flare rates are at their highest. Halfway through the cycle, the magnetic reaches its calmest point, and we see less activity. We use the relationship between flare rates and a star's point in the cycle to search for stellar cycles in distant stars. Kepler provides 4-year periods of observations for a large batch of stars. We examine the active stars, which are pulled from the Kepler data by Davenport (2016). For each active star, we determine a time vs flare-frequency plot. Using the Bayesian Information Criterion (BIC), we find a best fit polynomial for the plot. This BIC prevents over-fitting of the data by weighing the chi-squared vs the degree, heavily penalizing higher degree polynomials. A fit of degree 1 or higher highlights a trend in the frequency over time, meaning it's likely that the observed star has a stellar cycle. Understanding how common these cycles are, and how long each cycle lasts, will give insight into the magnetic fields of stars.