Photoionized nebulae, stars and the chemical evolution of galaxies
| Grant number: | 12/03479-2 |
| Support type: | Scholarships in Brazil - Post-Doctorate |
| Effective date (Start): | May 01, 2012 |
| Effective date (End): | October 31, 2015 |
| Field of knowledge: | Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics |
| Principal Investigator: | Walter Junqueira Maciel |
| Grantee: | Graziela Roswitha Keller Rodrigues |
| Home Institution: | Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil |
| Associated research grant: | 10/18835-3 - Planetary nebulae, stars and chemical evolution of stellar systems, AP.TEM |
Abstract Giving sequence to the work performed by the candidate during her Ph.D. and to the collaboration established with doctors Luciana Bianchi and James Herald from The Johns Hopkins University, we propose the expansion and enhancement of the grids of synthetic spectra that have been calculated by us and are useful to the analysis of observed spectra of hydrogen deficient post-AGB objects of the [WC] and PG1159 types. The synthetic spectra will be calculated using the non-LTE stellar atmosphere code CMFGEN, which considers spherically symmetric stationary expanding atmospheres, line blanketing, soft X-rays and wind clumping. We will include, in the models, several ionic species previously not considered in the literature, and will provide a uniform model set to fill in a niche in an important parameter regime, characterized by high temperatures and surface gravities and covering a range of mass-loss rates and terminal wind velocities. These grids will constitute a tool to facilitate the determination of stellar parameters, line identification and the planning of future observations and also to interpret changes in the stellar spectra as the star evolves through the central star of planetary nebula (CSPN) phase. We will use the grids in the analysis of ultraviolet spectra from the FUSE, HST and IUE space telescopes, which are available at the MAST archives and plan observation requests to complement these analysis with optical and additional UV spectra. The model grids will allow us to put constraints on the main stellar parameters. Following that, we will proceed further, by exploring other parameters not covered by the grids, as for example iron abundances and the inclusion, in the calculations, of less abundant ions. The grids of synthetic spectra comprising the far-UV, UV optical and infrared regions are being made available on-line to the community. In a complementary line of investigation, we will use the 3D Monte-Carlo radiative transfer code named Hdust in order to study the radiation transfer in inhomogeneous CSPNe winds for the purpose of determining the impact of wind clumping on the lines that constitute the main diagnostics of stellar parameters and of constraining the main physical parameters of these inhomogeneities. In this project, we will make intense use of the IAG's new and recently installed computer cluster. | |