Other
Scientific paper
Oct 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009phdt........82t&link_type=abstract
PhD Thesis, Instituto de Astronomia, São Paulo, Brazil, 2009
Other
Eta Carinae, Spectroscopy
Scientific paper
In this thesis, a multi-wavelength study on the cyclic events of η Carinae was performed. The presence of a hole in the polar region of the Homunculus was confirmed by the velocity maps of the [Fe II] λ12567 line. The blue-shifted component of the He I λ10830, detected towards the NW lobe, was mapped and it is in the equatorial plane. It was observed that within a short period of 206 days, centered on phase zero, the He I λ10830 line shows an increase in the maximum velocity of the absorption component, which reaches up to ˜1800 km/s. Such behavior favors orbital orientation with periastron passage around oposition. The Little Homunculus shows the same spatial distribution as the radio emission and considering that the radio flux comes mainly from the secondary, then the photon flux in the Lyman continuum is comparable to a star with spectral type in the range O5.5-O7. The variability of the narrow and broad lines from many spectral regions shows a well-defined period (2022.1 ± 0.6 days), which is also extremely stable along the last 60 years, during which the observed variations in the period are due to measurement errors. Using the narrow component of the He I λ6678 it was possible to determine the phase zero of the cycle #11 (T0 = 2452819.8). The spectroscopic events are a combination of two components: slow variation and collapse. The former is revealed by slow changes in the ionization level of circunstellar matter across the whole cycle and is associated to gradual changes in the wind-wind collision shock-cone (angular opening and gaseous content). The collapse component is restricted to around the minimum and is caused by a temporary collapse of the wind-wind collision shock. High-energy phenomena are sensitive only to the collapse component, while low-energy only to the slow variation component. Intermediate-energy phenomena are sensitive to both components. It was observed an anti-correlation between the Fe II λ6455 and ! He I λ7065, suggesting that the former is formed in the outer parts of the primary's wind, while the latter is associated to the secondary or to the wind-wind shock cone. The light curve of He II λ4686 shows two peaks before phase zero and another one short after it. The two peaks before phase zero are correlated to the peaks seen in the X-rays. However, the X-ray peaks occur 16.5 days before those seen in the He II λ4686 light curve. The most likely mechanism to explain the observed peak luminosity of the He II λ4686 is the creation of λ ˜ 1215 Angstrom photons by the extreme ultra-violet/soft X-rays photons, which are produced near the apex of the wind-wind shock-cone. Since this mechanism is extremely sensitive to the density, the most likely region to form the observed peak luminosity of the He II λ4686 is on the primary's side of the wind-wind shock-cone.
Damineli Augusto
Teodoro Mairan
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