About Me
Hi! I'm Charlotte Johnson, a rising senior at the University of South Carolina Honors College studying mathematics and astronomy. While I have always loved learning about space, I have also recently found that I absolutely love research. After this upcoming year, I plan to attend graduate school and continue pursuing a career in astronomy research. Outside of the classroom, I spend most of my time hiking, playing guitar, and crocheting. I also usually have my lop rabbit, Gus, by my side!
REU Project
This summer (2024), I'm working with Dr. Anne Lohfink to establish stronger connections between the X-ray corona and radio jet of black hole low mass X-ray binaries (LMXBs) using data from RXTE and Swift. While these LMXBs undergo enhanced accretion events, outbursts, we have observed corresponding changes in the X-ray and radio emission. However, the physics behind the connection are not well understood. In this project, X-ray and radio data from several LMXBs will be compared to determine if the X-ray corona and radio jet are strongly connected. Specifically, X-ray data will be fit to models in XSPEC to return a coronal height, which will be graphed against the radio jet break frequency and/or radio spectral index to best observe connections.
Past Research
Spring and Fall 2022
I was honored to work with Dr. Bram Boroson on a paper investigating the spectral energy distributions of binary X-ray sources. This project provided me with invaluable exposure to the research process, and truly sparked my interest in X-ray astronomy. I was able to model many sources in XSPEC, and contributed flux density and flux error calculations on these binary sources. This paper was published in September 2023 to the Astrophysical Journal Supplement Series (found here).
Spring 2023
I made connections with Dr. Varsha Kulkarni in astronomy journal club at school and was very grateful for the opportunity to complete an independent research project under her supervision. In this project, I was studying the chemical evolution of lensing galaxies of quadruply lensed quasars. I ended up focusing on 5 quadruply lensed quasars, chosen from the database found here. Although the list is quite extensive, I only selected quasars with four distinct images that also had data in the Sloan Digital Sky Survey (SDSS). I learned about using LineTools, checking for absorption lines, and normalizing spectra. In the end I produced a concise paper detailing my findings.
Research Project
Charlotte Johnson with Dr. Anne Lohfink
Understanding connections between the X-ray corona and jet break in black hole LMXBs
Credit: Universe Today
Although prior research has observed correlation between changes in the X-ray corona and radio jet as LMXBs progress through outbursts, it is not well understood whether the two are one and the same or not. To gain a better understanding of this, corona height and jet break frequency (or radio spectral index) will be compared throughout the progression of outbursts in several targets to observe if this trend exists. If the corona height and jet break continue to correspond through this evaluation, it may suggest that the X-ray corona acts as the base of the radio jet. There is also the possibility that the two are separate entities which act on their own, or there is a more complicated hybrid scenario where there may be some interaction.
This project will be using data from RXTE and Swift as well as published radio findings on our targets as they go through outbursts.