Full metadata
Title
A Photometric and Spectroscopic Analysis of the High-Energy Evolution of K Stars
Description
The balance between relative numbers, lifetime, and habitable zone (HZ) size of K stars (0.6 – 0.9 M⊙) in comparison with M (0.08 – 0.6 M⊙) and G (0.9 – 1.1 M⊙) stars makes them candidates to host “super-habitable” planets. Understanding the high- energy radiation environment of planets around these stars is crucial, since ultraviolet (UV) and X-ray radiation may cause severe photodissociation and ionization of the atmosphere, with the potential for complete erosion. In this thesis, I present the first broad study of the UV and X-ray evolution of K stars. I first focused on Galaxy Evolution Explorer (GALEX) and Ro ̈ntgen Satellit (ROSAT) photometric UV and X-ray evolutions of K stars and compared this with the age evolution of both early- (0.35 – 0.6 M⊙) and late-M (0.08 – 0.35 M⊙) stars. I found that the fractional UV and X-ray flux from M and K stars is similar; however, the wider and farther HZs of K stars mean that there is less incident UV radiation on HZ planets. Next, I led a spectroscopic study of 41 K stars using Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS) data to show that the UV line and continua emission show no decrease in flux beyond 650 Myr whereas early-M star flux declines by 150 Myr; therefore, the K star intrinsic UV flux is greater than early-M stars after this time. I suggest that this phenomenon is related to K star rotational spin-down stalling. Lastly, I revisited the GALEX and ROSAT data with newly-available distances from the Gaia mission for both K and M stars. I find that the UV flux for K stars is an order of magnitude higher for M stars at all ages and the flux in their respective HZs is similar. However, K star X-ray flux is an order of magnitude less in the HZ than for M stars. The age of decline shows a dependency on wavelength, a phenomenon which is not seen in either the early- or late-M star data. These results suggest thatK stars may not exhibit quite the advantage as HZ planet host stars as the scientific community originally thought.
Date Created
2022
Contributors
- Richey-Yowell, Tyler (Author)
- Shkolnik, Evgenya (Thesis advisor)
- Patience, Jennifer (Committee member)
- Jacobs, Daniel (Committee member)
- Bowman, Judd (Committee member)
- Young, Patrick (Committee member)
- Arizona State University (Publisher)
Topical Subject
Resource Type
Extent
pages
Language
eng
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.2.N.171952
Level of coding
minimal
Cataloging Standards
Note
Partial requirement for: Ph.D., Arizona State University, 2022
Field of study: Astrophysics
System Created
- 2022-12-20 06:19:18
System Modified
- 2022-12-20 06:19:18
- 1 year 10 months ago
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