Stellar activity and the planet-star connection

Biddle, Lauren Irene (2022) Stellar activity and the planet-star connection. Doctoral thesis, Northern Arizona University.

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Abstract

A major unanswered question in exoplanet science is the pathway for planetary formation and evolution. One approach to this problem is to accurately infer the histories of planets by comparing the demographics of late-age planetary systems to those of young systems. But, in contrast to the wealth of exoplanet discoveries at late ages, there are currently only a handful of confirmed planets at early ages (<10 Myr), and only one confirmed hot Jupiter orbiting a Classical T Tauri Star (CTTS). The severe deficit of young planets drives the motivation to find more of them. Doing so would provide concrete evidence for or against migration as well as timestamp the state of their atmospheric evolution. However, variability of CTTS is strong and occurs over a range of timescales, which can hinder the transit and RV detectability of young close-in planets. Intense magnetic activity in CTTS occurs in the form of long-lived cold spots and accretion hot spots which can mimic planetary signatures or drown them out entirely. Additionally, the high rate of energetic events generated by accretion shocks and flares is likely to affect the properties of the circumstellar disk and orbiting planets. The effects of stellar activity therefore offer incentive to characterize these sources of variability to (1) tease out the observational signatures of newly-formed planets and (2) understand the impact that high-energy magnetic events have on the evolution of planets and protoplanetary disks. A novel method offers a way detect close-in planets around CTTS based on the planet's interaction with the circumstellar disk, driving pulsed accretion onto the star over the timescale of the planet's orbit. It is therefore crucial to develop detailed diagnostics of accretion signatures so that more young planets can be identified with this method. Computational techniques can also aid in characterizing accretion signatures in addition to other sources of magnetic activity such as starspots and flares. The suite of tools developed in this work can help to accurately distinguish the nature of various astrophysical contributions to the energy environments of stellar and planetary systems.

Item Type:	Thesis (Doctoral)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Exoplanets; Planet Formation; Star Formation; Stellar Activity; T Tauri; Young Stars
Subjects:	Q Science > QB Astronomy
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > Physics and Astronomy
Date Deposited:	14 Jul 2022 17:16
Last Modified:	14 Jul 2022 17:16
URI:	https://openknowledge.nau.edu/id/eprint/5847

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