Abstract

Young stars consist of a prestellar core, a circumstellar disk, and an envelope. Material from the envelope accretes to the disk, and through angular-momentum loss or removal, disk material is transported onto the central star. Circumstellar disks are therefore central to both stellar growth and planet formation, making them crucial for understanding the early stages of stellar evolution. In low-mass pre-main-sequence stars, accretion proceeds through magnetospheric funnels that channel disk material onto the stellar surface, generating accretion shocks that result in an excess emission in the UV region and strong emission lines. Classical T Tauri stars (CTTSs) show highly variable accretion across multiple timescales. The origins of this variability remain unknown. In this seminar, I will present a detailed analysis of a classical T Tauri star using multiple emission-line diagnostics to investigate its accretion properties and discuss various line diagnostics related to star-disk interaction processes.