Papers by Gustavo A. Lima
Astronomy & Astrophysics, 2010
Context. Spectral observations of classical T Tauri stars show a wide range of line profiles, man... more Context. Spectral observations of classical T Tauri stars show a wide range of line profiles, many of which reveal signs of matter inflow and outflow. Hα is the most commonly observed line profile owing to its intensity, and it is highly dependent on the characteristics of the surrounding environment of these stars. Aims. Our aim is to analyze how the Hα line profile is affected by the various parameters of our model, which contains both the magnetospheric and disk wind contributions to the Hα flux. Methods. We used a dipolar axisymmetric stellar magnetic field to model the stellar magnetosphere, and a modified Blandford & Payne model was used in our disk wind region. A three-level atom with continuum was used to calculate the required hydrogen level populations. We used the Sobolev approximation and a ray-by-ray method to calculate the integrated line profile. Through an extensive study of the model parameter space, we investigated the contribution of many of the model parameters to the calculated line profiles. Results. Our results show that the Hα line is strongly dependent on the densities and temperatures inside the magnetosphere and the disk wind region. The bulk of the flux comes most of the time from the magnetospheric component for standard classical T Tauri star parameters, but the disk wind contribution becomes more important as the mass accretion rate, the temperatures, and the densities inside the disk wind increase. We also found that most of the disk wind contribution to the Hα line is emitted at the innermost region of the disk wind. Conclusions. Models that take into consideration both inflow and outflow of matter are a necessity to fully understand and describe classical T Tauri stars.
Proceedings of the International Astronomical Union, 2006
In order to detect variable stars in the well known star forming region, the Orion Nebula Cluster... more In order to detect variable stars in the well known star forming region, the Orion Nebula Cluster, a series of 22 exposures taken from November 1996 to October 1998, using the ESO 100/152cm Schmidt telescope, covering a field of 5° × 5° was analyzed. The films (Kodak Tech-Pan 4415 emulsions, effective spectral range from ~630 nm to 690 nm) were digitized by the SuperCOSMOS machine, the measurements calibrated to the R magnitude of the USNO B1.0 catalogue and differential photometry was performed throughout the whole field. In the process, a set of 260 stars that remained constant in the 22 films and were well distributed over the field was selected and used as comparison stars for the differential photometry of all the other stars in the field. Diverse statistical studies were performed in order to characterize the type and degree of variability of the objects. The 22 films, all exposed for 30 minutes each, were stacked together at our request by the SuperCOSMOS team, producing perh...
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Papers by Gustavo A. Lima