Studying Be disk dynamics using Polarimetry and Spectroscopy: the case of alpha Eri

• Grant number: 23/12720-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2024
• End date: December 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Alex Cavaliéri Carciofi
• Grantee: Clara Amorim Navarro
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 18/04055-8 - High precision spectroscopy: from the first stars to planets, AP.TEM

Abstract

Be stars are main sequence B-type stars characterized by emission lines in their spectra. They exhibit high rotation rates and non-radial pulsations, resulting in the formation of an outwardly diffusing gaseous Keplerian disk. These disks cause the distinguishing observational features of Be stars, including emission lines, infrared excess, and linear polarization.Current models of Be star disks primarily explain the dynamics of the innermost portion of the disk, as tracked by photometry in the visible domain. However, significant differences in dynamics exist in the outermost portion, that is revealed by spectroscopy. This research proposal aims to bridge this gap by studying the intermediate part of the disk using polarimetry.This project will develop the first dynamical model for a Be star disk using polarimetry. The nearest Be star, Achernar (alpha Eri), will be the primary target for this study. This star recently underwent a transition from a diskless phase to a full disk and back to a diskless state, providing a unique opportunity to examine the complete formation process of the disk in detail. To achieve our goals, we propose utilizing the time-dependent hydrodynamic code SINGLEBE in conjunction with the three-dimensional non-LTE Monte Carlo radiative transfer code HDUST. Our objectives encompass three key aspects: 1) Developing a dynamical model for Achernar by modelling its polarimetrically well-documented disk event.2) Extending the developed model to other observables, particularly spectroscopy.3) Investigating how different parts of the disk behave, as tracked by different observables.