Dissertations, Theses, and Capstone Projects

Date of Degree

6-2024

Document Type

Thesis

Degree Name

M.S.

Program

Astrophysics

Advisor

Ruth Angus

Advisor

Dax Feliz

Subject Categories

Astrophysics and Astronomy | Stars, Interstellar Medium and the Galaxy

Keywords

Gaussian Process, Stellar rotation, rotation periods, LSST

Abstract

Stellar rotation is a readily observable characteristic that plays a crucial role in the generation and activity of magnetic fields through a process known as a magnetic dynamo. For low mass main sequence stars, they exhibit fully convective interiors, giving rise to a distinct dynamo mechanism compared to solar-type stars. Examining the rotational speeds of these stars can offer valuable insights into the workings of these mechanisms. To measure these rotation periods, we developed a pipeline to analyze 192 archival light curves of low mass stars observed by the Zwicky Transient Facility (ZTF) by utilizing a combination of Lomb-Scargle and a RotationTerm Gaussian Process Kernel to detect and model the stellar rotation in our ZTF light curves. We produce a catalog of measured rotation periods that range from $\sim$1-190 days. With this sample of high-fidelity, visually inspected stars with well-constrained measured rotation period, we compare our methodology with traditional methods of rotation period detection (Lomb-Scargle). We find that using our methodology yields greater sensitivity to detecting long term quasi-periodicity than with Lomb-Scargle detections of sinusoidal variations. Out of the sample of 192, we measure 105 long term rotation periods not detected by traditional methods, and 58 rotation periods that agree with Lomb-Scargle measurements. Accurate rotation periods could not be recovered from the remaining 29 stars, due to the absence of a strong enough rotation signal for our method. Upon visual confirmation, we find that the Gaussian process method may be more sensitive to harmonics, and future work is planned to correct for this.

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