On The Interpretation Of Oxygen Line Emission In Comets And In SN 1987A

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Session 8 -- Solar Observations and Instrumentation
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[8.03] On The Interpretation Of Oxygen Line Emission In Comets And In SN 1987A

S. O. Kastner (MSC., Inc) and A.K Bhatia (NASA/GSFC)

Present interpretations of neutral oxygen spectra in various astrophysical sources often invoke the H Ly-$\beta$/ O I fluorescent process to explain the presence of lines originating in higher levels. A basic analysis of the cascade populations and emissions to be expected from the process is carried out and applied to an ultraviolet spectrum of Comet Austin and to near-infrared spectra of the supernova SN 1987A, in which lines are present which have been interpreted as O I fluorescent lines. Some inconsistencies and consequences are pointed out including an interesting reversal of the usual roles of allowed and forbidden lines under optically thick conditions. It is concluded that the fluorescent mechanism probably did not operate in Comet Austin, nor in other comets; and that it has also not operated in SN 1987A. For Comet Austin in particular this raises questions concerning the origin of the observed high-excitation lines in the vicinity of 1042 and 1128 \AA. In case of SN 1987A the apparent presence of lines of the O I quintet system appear to suggest a selective excitation mechanism.

A white light coronagraph was launched into orbit aboard the space shuttle OV 103 (Discovery) on 7 April 1993. This device was one of two instruments included in the SPARTAN 201-1 payload, a completely autonomous sub-satellite deployed from the shuttle for a period of about 47 hours. During this period of deployment data were collected by the white light coronagraph (WLC) and the SAO-supplied Ultraviolet Coronagraph (UVC) for investigations of the density, temperature, mass and bulk velocity distributions found in large scale coronal structures.

The WLC system is an externally occulted coronagraph system which incorporates a rotating half-wave plate polarimeter, and the image data is used to infer the brightness, the polarized brightness and degree of polarization of the white light emission from the solar corona. These data are in turn used to infer estimates of the K- and F-coronal brightness and density distributions.

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