Análise da interacão disco-estrela no sistema estelar jovem V354 Mon

• Ano de defesa: 2016
• Autor(a) principal: Nathalia Nazareth Junqueira Fonseca
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Astrofísica; Física; Fotometria
• Link de acesso: http://hdl.handle.net/1843/BUOS-AR4JKN

We present the study of star-disk interaction in the classical T Tauri star V354 Mon, a member of the young stellar cluster NGC 2264. As part of an international campaign of observations of NGC 2264 organized from December 2011 to February 2012, high resolution photometric and spectroscopic data of this object were obtained simultaneously with the Chandra, CoRoT, and Spitzer satellites, and ground-based telescopes, such as CFHT, VLT/ESO, and USNO. The light curve of V354 Mon shows periodic brightness variation, with minima that change their shapes every 5.21 day-rotational cycle. This modulation occurs simultaneously from u band to 4.5 m, but the minimum depth decreases as the observed wavelength increases, and the system becomes bluer with increasing flux. We found evidence that the H emission line profile varies according to the period of photometric modulation, indicating that the same phenomenon is responsible for both variations. Such correlation between the changing in the emission line and the light curve modulation was also identified in a previous observational campaign on the same object, where we verified that the H redshifted absorption was more pronounced in the moments of lower brightness. Therefore during the photometric minima the accretion flux was projected on the stellar photosphere in our line of sight. In the new campaign, the spectra with evidence of redshifted absorption are observed outside the photometric minima, which would indicate that the accretion funnel is distorted. We concluded that material non-uniformly distributed in the inner part of the disk is the main cause of V354 Mon brightness variation. This assumption is supported by the fact that the system is seen at high inclination. It is believed that the stellar magnetosphere, inclined with respect to the rotation axis, dynamically interacts with the circumstellar disk material, producing a distortion in its inner part. This phenomenon, predicted by magnetohydrodynamic numerical simulations, was also observed in the classical T Tauri star AA Tau. A model of occultation by circumstellar material was applied to the photometric data and, from comparing the parameters of the obscuring structure during both observational campaigns, we notice that it remained stable, although some changes occur at each cycle and more dramatically over the years. After removing the contribution of the disk emission, the optical and infrared amplitudes become similar, which indicates that the material in the inner part of the disk is opaque.