Resonance-enhanced two-photon ionization (RETPI) of Si II and an anomalous, variable intensity of the 1892 Si III] line in the Weigelt blobs of η Carinae
Lund Observatory, Lund University, PO Box 43, 22100, Lund, Sweden e-mail: firstname.lastname@example.org
2 Institute of Spectroscopy, Russian Academy of Sciences, 142190 Troitsk, Moscow region, Russia
Accepted: 21 February 2006
Context.The Si III] 1892 Å intercombination line shows an anomalously high intensity in spectra of the radiation-rich Weigelt blobs in the vicinity of Eta Carinae. The line disappears during the 100 days long spectral events occurring every 5.5 years.
Aims.The aim is to investigate whether resonance-enhanced two-photon ionization (RETPI) is a plausible excitation mechanism for the Si III] λ1892 line.
Methods.The possible intensity enhancement of the λ1892 line is investigated as regards quasi-resonant intermediate energy levels of Si II.
Results.The RETPI mechanism is effective on in the radiation-rich Weigelt blobs where the two excitation steps are provided by the two intense hydrogen lines Lyα and Lyγ.
Key words: atomic processes / radiation mechanisms: non-thermal / HII regions / stars: individual: η Carinae
© ESO, 2006