The Spectra of the Supernovae in IC 4182 and in NGC 1003.

Abstract

view Abstract Citations (85) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Spectra of the Supernovae in IC 4182 and in NGC 1003. Minkowski, R. Abstract Spectrograms of supernova IC 4182 have been obtained until 339 days after maxi- mum and of supernova NGC 1003 until 115 days after maximum. The spectra of these two supernovae differ only in details of minor importance. They may be interpreted as consisting of wide, partly overlapping emission bands; on the earlier spectrograms the width of the narrowest details is about 100 A. After an initial period of about two weeks the spectrum divides into two parts. That to the red of X 5000 undergoes pro- nounced changes; bands appear and disappear in a manner resembling the behavior of the emission bands in the spectra of ordinary novae. Below A 5000 a permanent pattern forms, consisting of one strong and several fainter bands, which shifts, as a whole, gradually toward the red without any significant changes in its intensity distribu- tion. The two parts of the spectrum show pronounced changes in their relative intensi- ties, which emphasize their independence. The red part strengthens at first, and about 40 days after maximum becomes preponderant; it then fades to a minimum intensity about i6o days after maximum, reappears at almost its initial strength about 20 days later, and finally fades out slowly. These changes are not accompanied by any signifi- cant change of the pattern in the blue. About i8o days after maximum two narrow bands, with a width of less than ~o A, appear at X 6299 and X 6359. Their intensity relative to the rest of the spectrum increases slowly, and they become finally the only observable features in the red. A comparison of the spectra of supernovae IC 4182 and NGC 1003 with those of the five earlier supernovae for which spectroscopic observations are available indicates that the spectra of all supernovae are practically identical in their composition and in their transformations. A possible exception is S Andromedae, for which, however, only visual observations were made. This similarity extends apparently to even the amount of the red shift in the blue part of the spectrum, which for supernova IC 4182, 339 days after maximum, reached a value of about 125 A. If the bands are ordinary emission lines, the red shift, which is not accompanied by a change in the width of the bands, cannot be explained as due to a Doppler effect produced by an outward flow of matter without assuming an excessive darkening toward the limb. The explanation of the red shift as due to an increase in the gravitational potential at the surface of the star, in accordance with Zwicky's hypothesis of a collapse of the star, entails the assumption that the bands are negative absorption lines formed by induced transitions in a forbidden line of a highly ionized atom. But this assumption also permits, with fewer restrictions, an interpretation of the red shift as the result of a Doppler effect. The two narrow bands in the red are probably to be identified as the [Oil lines X 63co and X 6364. At present no other identifications can be proposed without reservation. The absence of hydrogen and helium lines indicates a very high degree of ionization; thus, all the bands may be of unknown origin Publication: The Astrophysical Journal Pub Date: March 1939 DOI: 10.1086/144037 Bibcode: 1939ApJ....89..156M full text sources ADS | data products NED (8) Related Materials (1) Reprint: 1939CMWCI.602....1M