By NelmaS on Dom, 12/06/2016 - 19:48
Fátima López Martínez
T~Tauri stars (TTS) are young and low-mass pre-main sequence stars. They have a surrounding disk as well as strong and complex magnetic fields. The disk is truncated near the corrotation radius due to its interaction with the stellar magnetic field. The material in the inner part of the disk is ionized by the stellar radiation and channelled through the magnetic field lines. The gas from the disk is accelerated to almost free-fall velocity before it reaches the stellar surface forming an accretion shock. The ultraviolet luminosities of TTS exceed by 1-2 orders of magnitude those observed in main sequence stars of the same spectral types. This excess is associated with the accretion process that transports material onto the stellar surface enhancing the flux radiated by magnetospheric/atmospheric tracers. The energy produced in the atmosphere and magnetosphere is released mainly in the ultraviolet range.
The study of TTS provides some important clues about young stars, planetary system formation and their early evolution. The spectra of T~Tauri stars show peculiar features, mainly in the ultraviolet range. Most of the TTS emission is produced in a region of the magnetosphere with temperatures of about 10000~K. In this talk I will speak about the work developed in my thesis, in which I analysed ultraviolet spectral lines formed in regions with those temperatures, (C~II], Fe~II], Si~II] and Mg~II). The study of these lines allowed me to determine some constraints to the magnetosphere properties in TTS.
22 de junho de 2016 | 13:30
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto