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[Ti II] and [Ni II] Emission from the Strontium Filament of eta CarinaeWe study the nature of the [Ti II] and [Ni II] emission from the so-called strontium filament found in the ejecta of eta Carinae. To this purpose we employ multilevel models of the Ti II and Ni II systems which are used to investigate the physical condition of the filament and the excitation mechanisms of the observed lines. For the Ti II ion, for which no atomic data was previously available, we carry out ab initio calculations of radiative transition rates and electron impact excitation rate coefficients. It is found that the observed spectrum is consistent with the lines being excited in a mostly neutral region with an electron density of the order of 10(exp 7) per cubic centimeter and a temperature around 6000 K. In analyzing three observations with different slit orientations recorded between March 2000 and November 2001 we find line ratios that change among various observations, in a way consistent with changes of up to an order of magnitude in the strength of the continuum radiation field. These changes result from different samplings of the extended filament, due to the different slit orientations used for each observation, and yield clues on the spatial extent and optical depth of the filament. The observed emission indicates a large Ti/Ni abundance ratio relative to solar abundances. It is suggested that the observed high Ti/Ni ratio in gas is caused by dust-gas fractionation processes and does not reflect the absolute Ti/Ni ratio in the ejecta of eta Carinae. We study the condensation chemistry of Ti, Ni and Fe within the filament and suggest that the observed gas phase overabundance of Ti is likely the result of selective photo-evaporation of Ti-bearing grains. Some mechanisms for such a scenario are proposed.
Document ID
20070016603
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bautista, M. A.
(Centro de Fisica, IVIC Caracas, Venezuela)
Hartman, H.
(Lund Univ. Sweden)
GUll, T. R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Smith, N.
(Colorado Univ. Boulder, CO, United States)
Lodders, K.
(Washington Univ. Saint Louis, MO, United States)
Date Acquired
August 23, 2013
Publication Date
June 12, 2007
Subject Category
Astronomy
Report/Patent Number
astro-ph/0606275-v1
Funding Number(s)
CONTRACT_GRANT: HF-01166.01A
CONTRACT_GRANT: NNG04G157A
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Public Use Permitted.
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