The historical record for Sirius: evidence for a white-dwarf thermonuclear runaway?

Abstract

Schlosser and Bergmann¹ recently presented evidence that in medieval times Sirius was a bright red star, rather than the present bluish-white star, from which they have suggested that Sirius B is a recently born white dwarf. However, their model poses severe evolutionary problems. We present the results of our attempts to detect possible planetary nebula ejecta toward Sirius, using data obtained by the International Ultraviolet Explorer (IUE) satellite. Based upon these results and in the light of recent advances in understanding white-dwarf evolution, we propose that Sirius B underwent a recent thermonuclear runaway event, triggered by a diffusion-induced CN reaction, to explain the historical behaviour of this star.