Modelling the Spectra of Stars with Stellar Spots for the GALAH Survey

Overview 

Stellar spots are cooler regions on a star’s surface that can affect the observed spectrum by altering light distribution. This is particularly relevant for active stars, where spots can cover a significant portion of the surface, and can bias our measurements. For surveys like GALAH, understanding stellar spots is essential for improving the accuracy of chemical abundance measurements. This project aims to model the spectra of stars with spots, combining a spot spectrum with flux F_spot (with temperature T_spot) and a stellar spectrum with flux F_star (with temperature T_star), where f_spot and (1-f_spot) represent the fractional contributions. 

Objectives 

1. Literature Review: Study existing research on stellar activity, spectral modeling, and spot effects on spectra. 
2. Identify Active Stars: Select stars with indications of stellar spots in GALAH data and retrieve their spectra. 
3. Synthetic Spectra: Use neural networks to create synthetic spectra for both stars and spots. 
4. Fit Combined Spectra: Model combined spectra to fit GALAH data and evaluate the impact of stellar spots on abundance measurements. 

Literature

Methodology by Wilson et al. (2023) 

Motivation of the GALAH Survey by De Silva et al. (2015)

How stellar spectra are created for GALAH by Buder et al. (2024)

Supervisors

Maja Jablonska (primary supervisor)

Dr Sven Buder (formal supervisor)

Image: An sketch of a star with a stellar spot that will cause a different spectrum than a spotless star

Image