Stellar Rotation of Young Stars
Creators: name: Serna, Javier
name: Hernández, Jesús
Publisher: name: Zenodo
Year: 2023

description: The Orion star-forming complex is an ideal astrophysical laboratory with a large number of spectroscopically confirmed stars as low-mass young objects (T Tauri stars) in a wide range of ages (1-10 Myr), well suited to perform a systematic study of stellar rotation during the first million years of stellar life. In this phase, protoplanetary disks that are linked via accretion columns to the stars regulate the evolution of angular momentum. The central objective of this doctoral thesis is to embark upon an unprecedented exploration of stellar rotation within T Tauri stars. To achieve this, we combine two approaches to conduct this study, developing tools for the robust estimations of stellar rotation measurements:
From an observational perspective, we use projected rotational velocity (v sin(i)) estimations from the APOGEE-2 collaboration, as well as individual masses and ages derived from the HR diagram and evolutionary models. The v sin(i) estimates were checked using a tool developed in this thesis that uses Fourier Transform methods. Our study also includes rotational periods estimated from TESS light curve analysis. For low-mass stars, we found an empirical evolutionary trend of v sin(i) that indicates that accreting disks regulate stellar rotation on timescales of about 6 Myr, which is the timescale in which most of the T Tauri stars lose their inner disk. Our results provide important constraints to models of rotation in the early phases of the evolution of young stars and their disks. This work was published in the ApJ Journal (Serna et al., 2021).
From a theoretical perspective, we developed a tool to generate grids of stellar rotation models, incorporating the star-disk interaction and magnetospheric ejections in the accretion-powered stellar winds framework to investigate the evolution of the stellar rotation rate as a function of the mass, the magnetic field, and stellar wind. Our results confirm that T Tauri stars' v sin(i) measurements agree with the rotation rates provided by our models. Additionally, we find that the evolution of v sin(i) with age might be regulated by variations in (a) the intensity of the magnetic field and (b) the fraction of the accretion flow ejected in magnetic winds. This work is currently under its second revision in ApJ Press.
In addition, we present a user-friendly web application called TESSExtractor, which facilitates the extraction and analysis of TESS light curves for various astrophysical studies, including stellar rotation. This tool is already available and is within the scope of any person. The paper related to TESSExtractor will be submitted to AJ Journal this year. Indeed, TESSExtractor is already intensively used in two Ph.D. projects of our collaboration groups (e.g., Rodrı́guez-Feliciano et al. (2023), Batista et al. in preparation).
This research has provided a general understanding of rotation in young stars in connection with their disks, providing valuable insights into the physical processes involved in T Tauri stars. Furthermore, this work offers models to forecast physical parameters such as magnetic field and mass loss rate for T Tauri stars. Moreover, it provides tools to estimate rotation observables using photometry and spectroscopy, extending their utility to diverse users.