Optical Studies of Cassiopeia a. III. Spectra of the Supernova Remnant
1971; IOP Publishing; Volume: 165; Linguagem: Inglês
10.1086/150913
ISSN1538-4357
Autores Tópico(s)Astro and Planetary Science
Resumoview Abstract Citations (119) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Optical Studies of Cassiopeia a. III. Spectra of the Supernova Remnant van den Bergh, Sidney Abstract The optical remnant of Gas A consists of two components: (1) a system of about too fast-moving knots and (2) approximately thirty quasi-stationary flocculi. New spectroscopic observations of both types of objects are reported in this paper. These observations are supplemented by earlier data that generously made available by Dr. Minkowski. The following emissinn lines have been observed in the spectra of moving knots: [0 i] 630O, 6364; [0 ii] , 3729,7320, 7330; [Oiii] , 4959, 5007; [S Ir 4069, 4076, 6716, 6731; and [Ar iii] 7136. The relative intensities of these lines differ from knot to knot. The optical flare, which extends beyond the radio-emitting shell, radiates [S ii] but not [0 liii (strong interstellar absorption renders [0 ii] 3727 invisible in this feature). Over the main body of the optical remnant of Gas A, [0 1], [0 ii], [0 III], and [S ii] have a rather similar large-scale distribution. For all observable moving knots 1(6716) 1(6731). This indicates that n > 3000. Such a high density is also required by the short decay time-scale of moving knots. Ha and [N ii X654S, 6584 have not been detected in moving knots. Some moving knots are loosely organized into filaments. The velocity differences between individual knots in one such filament approach 3000 km . This observation suggests that massive gas clouds are still being accelerated to velocities of a few thousand km at the present time. Only Ha and [N ii] have so far been observed in the spectra of quasi-stationary fiocculi. Individual fiocculi exhibit motions of up to 0' 02 . These motions do not seem to point away from the center of expansion of Gas A. Intercomparison of radial velocities and proper motions of moving knots yields a very uncertain distance of 2.8 kpc. Such a distance would place Gas A just behind the spine of the Perseus spiral arm. It is suggested that the system of flocculi surrounding Kepler's supernova was formed when a preexisting circ'nmstetlar envelope was engulfed by the expanding shell of the supernova of 1604. The observed overabundance of nitrogen in the quasi-stationary flocculi associated with Gas A suggests that these objects were also formed by compression of circumstellar material. The total mass of all quasistationary flocculi in Gas A is estimated to be about 5 X 10 ' g. Publication: The Astrophysical Journal Pub Date: May 1971 DOI: 10.1086/150913 Bibcode: 1971ApJ...165..457V full text sources ADS | data products SIMBAD (1) Related Materials (7) Part 1: 1970ApJ...162..485V Part 2: 1971ApJ...165..259V Part 4: 1971ApJ...167..223P Part 5: 1976ApJS...32..351K Part 6: 1983ApJ...268..129V Part 7: 1985ApJ...293..537V Part 8: 1986ApJ...307..723V
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