UNDERSTANDING ACCRETION ACTIVITY IN YOUNG STARS USING SDSS-V BOSS SPECTRA

Abstract

Stellar spectra are a valuable tool for understanding young pre-main sequence stars. Some spectral lines, such as Li I, can be a direct indicator of stellar youth while other lines, e.g., H$\alpha$ or Ca II, can be used as a tracer of either disk accretion or magnetic activity that is also heightened in young stars. In our research, we used low resolution optical spectra collected from the fifth iteration of Sloan Digital Sky Survey (SDSS-V) to develop techniques to perform a spectroscopic identification of YSOs and to analyze their properties. We present a data-driven pipeline, LineForest, that autonomously measures the equivalent width of 52 different lines in the optical spectra, including Li I, Balmer series, Paschen series, and a number of lines that can be seen in emission due to accretion. Using these lines, we construct a classifier that, to date, has confirmed the youth of $>$18,000 stars, including $>$5500 classical T Tauri stars (CTTSs). Through modeling the decrement of the lines in the Balmer series, we estimate the properties of the accretion stream of these CTTSs, such as the temperature of the accretion flow and its surface density. Using the veiling measurements, we further explore the accretion properties of these stars. We particularly analyzed how veiling correlates with other physical properties, such as H$\alpha$ equivalent width, age, and effective temperature, to gain insights into the accretion mechanisms. We compared these results with existing theoretical models to evaluate their consistency.