Common Features of the Optical Continua associated with Violent Cosmic Events

Abstract

THE purpose of this communication is to point out a similarity in the optical continua of several objects, all associated with violent events, but which otherwise have a diverse character. The objects are the nucleus of the Seyfert Galaxy NGC 4151, the galactic, nova-like object η Carinae, the Crab Nebula and the quasi-stellar radio source, 3C748. (The term nova-like is to some extent descriptive of the spectrum. In using it, we do not mean to imply a mechanism for the outburst in η Carinae. This outburst has involved energies characteristic of supernovae and, unlike either supernovae or novae, has a time scale of the order of a century.) The optical spectrum of NGC 4151 has been discussed by Seyfert¹ and Woltjer², that of η Carinae by Thackeray³, that of the Crab Nebula by Woltjer⁴ and Mayall⁵, and that of 3C48 by Greenstein and Schmidt⁶. The emission lines in all of these spectra show, as a common feature, evidence of internal motions as large as a few thousand km/sec. We indicate in Table 1 some of the principal observed features of these objects.