Circumstellar envelopes of intermediate mass young stars

Author(s)

Rodrigo Georgetti Vieira

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD)
• Defense date: 2012-09-20

Examining board members

Jane Cristina Gregorio Hetem; Sílvia Helena Paixão Alencar; Alex Cavalieri Carciofi; Augusto Damineli Neto; Silvia Lorenz Martins

• Advisor: Jane Cristina Gregorio Hetem

Abstract

Herbig Ae/Be (HAeBe) objects are intermediate mass (2 -10 Msun) stars in the pre-main sequence. Some of their properties remain not well understood to date. Only a full multi-wavelength study is able to reveal a reasonable scenario for their circumstellar material. The purpose of the present work is to study the structure, composition and evolution of these circumstellar environments. To address this issues, the sample of HAeBe candidates detected by the Pico dos Dias Survey (Vieira et al., 2003) was adopted. To avoid the contamination by more evolved stars, we developed an analysis based on two-color diagrams, extinction values and spectral features. The chemistry of the circumstellar dust was studied based on Infrared Space Observatory spectra available to our sample. The silicate feature around 10 micron revealed evolutionary information of the circumstellar material. The evolutionary stage of the more embedded sources was determined by estimates of their envelope masses. This study indicates almost all of this sub-sample to be in the intermediate phase between Class 0 (Menv>>Msun) and Class I (Menv<Msun). Mid-infrared images, retrieved from archive data, introduced morphological constraints to the orientation and extension of the disk associated to PDS340. The available observations for several wavelengths revealed some characteristics of the structure and evolution of the circumstellar material associated to HAeBe stars. The perspective of the development of a complete model, which encompasses all the available data, is described in the conclusion of this work. (AU)

• FAPESP's process: 08/01533-4 - Circumstellar envelopes of intermediate mass young stars
• Grantee: Rodrigo Georgetti Vieira
• Support Opportunities: Scholarships in Brazil - Doctorate