Mid-infrared spectroscopy of nearby red giants

Abstract

As low- to intermediate-mass stars (< 8 solar masses) evolve along the asymptotic giant branch they experience extreme mass loss due to strong stellar winds, ultimately resulting in stellar death. The driving mechanism for mass loss is not entirely understood, however it is believed to be due to a combination of powerful Mira-like pulsations and thick dusty envelopes. Using high resolution infrared spectroscopy from VISIR, observations of 179 giant stars with L > 700 L (solar) within 300pc of Earth have been obtained. Of these, 33 stars have been identified as potentially dusty. Using the modelling programme DUSTY, dust compositions and mass-loss rates have been determined for five objects, ranging from 10^(-9) to 10^(-6) solar masses per year. Interpretation of these results suggests AGBs spend a longer time evolving at low mass-loss rates, then experience a short period of high mass loss. Analysis of the non-dusty stars has also revealed information about the warm molecular layer of these late-type stars.

Date of Award	6 Jan 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Rhian Jones (Supervisor) & Romain Tartese (Supervisor)