Optical Studies of Cassiopeia a.IV. Physical Conditions in the Gaseous Remnant
Abstract
Emission-line intensity ratios have been used to study physical conditions in the remnant Cas A. The following results are obtained: (1) In the system of fast-moving knots, oxygen and argon are overabundant by a factor of at least 70 with respect to hydrogen and nitrogen. (2) Nitrogen is found to be overabundant in quasi-stationary flocculi. This suggests that these flocculi were formed from material that was ejected from the outer layers of the presupernova before its explosion in A.D. 1667. The quasistationary flocculi in Cas A may therefore resemble the remnant of Kepler's supernova, which also seems to have been formed from circumstellar material that was engulfed by a supernova shell. (3) The observed emission-line intensity ratios indicate that the absorption in the direction of Cas A lies in the range 5 < Av < 7 mag. (4) The hypothesis that the faint H ii region surrounding Cas A was produced by the supernova of A.D. 1667 yields a lower limit 1 X 10 ergs for the total ultraviolet energy radiated during the explosion of Cas A.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1971
- DOI:
- 10.1086/151024
- Bibcode:
- 1971ApJ...167..223P