Other
Scientific paper
Feb 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000mst...........b&link_type=abstract
Msc. Thesis, Observatorio Nacional/MCT (Brazil)
Other
Spectroscopic Analysis, B[E]Supergiants, Lbv, Individual Objects: Hd87643, Hd89249, Hr Car, Gg Car And Cpd-529243
Scientific paper
The upper HRD is populated by massive stars. These objects have, as a characteristic, a substantial mass loss, due mostly to radiation pressure, throughout their whole lives. However about the evolution of these stars, the only secure informations are that they are B or O type stars in the zero age main sequence and they finish their lifes in a supernova explosion. The difficulties, to ascertain the others evolutive stages of these objects, are that they do not exhibit (in most cases) photosferic absorption lines, due to their complex circumstellar medium, preventing the estimate of the physical parameters. Moreover, these phases are relatively "shorts", and so we have a little sample of objects. Among the "short" phases, we detach the B[e] Supergiant (B[e]sg) and the Luminous Blue Variable (LBV) phases. The stars in these two evolutive stages show similar characteristics in the optical spectrum. They are, the presence in B type stars, of forbidden emission lines of [FeII], [OI] (in the B[e]sg) and [NII] (in the LBV). The presence of strong Balmer emission lines, low excitation permitted emission lines of predominantly low ionization metals, e.g. FeII in the optical spectrum and a strong near or mid-infrared excess due to hot circumstellar dust. In general, the Balmer lines (and sometimes HeI and FeII lines too) show P-Cygni profiles, due to mass loss. In despite of the similarities, the LBV are separated of the B[e]sg, due to strong spectral-photometric variability. Then it is necessary a detailed spectroscopical analysis of some objects, to obtain not only a better classification, like a B[e]sg or LBV, but useful informations to perform in the future a physical model. We have done such analysis for five stars in the Galaxy: HD 87643, HD 89249, HR Car, GG Car and CPD-529243. With our new data, others presented by literature, and a long time monitoring of these stars, we believe that in the near future, it will be possible to determine a correct classification to these objects. Our data (that were analised and showed in this thesis) were obtained in low and middle dispersion, in ESO and LNA, respectively. They are concentrated in the optical range, but there are also, spectra in the near IR (centered in 10000 Å). The analysis were based on the lines identification and on the acquisition of the equivalents widths and the fluxs. It is important to say, that in all the objects, we found the B[e]sg and LBV optical characteristics. And it was possible using the interstellar NaI lines, to acquire an estimative of our stars sample distances.
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