Spectral Synthesis of Rapidly Rotating Massive-Stars

• Grant number: 11/13772-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2011
• End date: September 30, 2013
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Alex Cavaliéri Carciofi
• Grantee: Jorge Miguel Ribeiro
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The interferometric group of IAG/USP has developed several theoretical tools to study a particular class of hot stars called Be stars. Those stars are very common, and possess the peculiar characteristic of having very high rotation rates, close to the break-up speeds. Another peculiarity is that Be stars often possess a circumstellar disk. The fact that many Be stars are very nearby (less than 200 pc away) makes them ideal targets for modern interferometers that can angularly resolve their disks and even their photospheres with great detail, opening a new window in the study of the physics of circumstellar disks and rapidly rotating stars.The main theoretical tool of our group is the radiative transfer code HDUST, which uses the Monte Carlo method to solve the transfer of polarized radiation in disk. The basic task of HDUST is to convert the structural information of a given physical model to astrophysical observables (images, spectra, etc.), thus allowing for a detailed comparison between theory and observations. A particularly important aspect of the code is its ability to treat the geometrical deformation of rotating stars and their non-uniform flux distribution due to the von Zeipel effect. Presently, HDUST treats the latitude-dependent emergent flux with Kurucz spectra, which is enough to provide an accurate description of the emergent spectral energy distribution but are not enough to model the photospheric absorption line profiles. The main goal of this Research Project is to develop an interface between HDUST and the model atmosphere code TLUSTY. In its final form the resulting code will be able to accurately synthetize the photospheric line profiles of rotating stars, which will have significant impact in our ability to simulate astrophysical observables.