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Nikolay Walters
I was keen to continue with astrophysics, yet I wanted to center on the more data-driven approach to research questions.
5 January 2019
Project title:听Active chromospheres in white dwarfs听
Research Group: Astrophysics
厂耻辫别谤惫颈蝉辞谤(蝉):听Prof Jay Farihi听&补尘辫; Prof Sergey Yurchenko
滨苍迟谤辞诲耻肠迟颈辞苍:听
I graduated from 香港六合彩 with an Msci in Physics where I achieved first class honours. My masters project was on identification of carbon stars using machine learning techniques. I worked with optical spectra acquired by Sloan Digital Sky Survey (SDSS) and used a decoder from a trained variational autoencoder network to aid a selection of machine learning classifiers. By the end of my project I was keen to continue with astrophysics, yet I wanted to center on the more data-driven approach to research questions. CDT in DIS proved to be a good match, allowing me to both focus on astrophysics while continuing to enrich my understanding of data and its applications in the field.听
Project description:听听
My PhD project mostly focuses on a rare class of magnetic white dwarfs. Despite thousands of spectroscopically-identified white dwarfs, when I started my PhD only one isolated and cool star was known to exhibit Balmer emission. Six such systems are now known, suggesting a new class of chromospherically-active white dwarfs. Furthermore, their close grouping on the Hertzsprung-Russell diagram points to a single star evolutionary origin, but with an unknown source of chromospheric heating. The common characteristics of the class are important pieces of the puzzle and include apparent isolation, fast rotation, and magnetism. In my work, I study photometric, spectroscopic, and spectropolarimetric observations of the class prototype, GD 356, where the data point to a temperature inversion similar to that seen in the Sun and cool dwarf stars. Despite the unknown physics, there are several testable predictions if the emission has an intrinsic origin. My current and future work focus on constraining any evolution-activated chromospheric phenomena, with implications for not only this whole class of stellar remnants, but for magnetic stars in general.听
First year group project: NCC Group
Placement:听NCC Group
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