SN 1999ga: a low-luminosity linear type II supernova?

摘要

Context. Type II-linear supernovae are thought to arise from progenitors that have lost most of their H envelope by the time of theexplosion, and they are poorly understood because they are only occasionally discovered. It is possible that they are intrinsically rare,but selection effects due to their rapid luminosity evolution may also play an important role in limiting the number of detections. Inthis context, the discovery of a subluminous type II-linear event is even more interesting.Aims. We investigate the physical properties and characterise the explosion site of the type II SN 1999ga, which exploded in thenearby spiral galaxy NGC 2442.Methods. Spectroscopic and photometric observations of SN 1999ga allow us to constrain the energetics of the explosion and toestimate the mass of the ejected material, shedding light on the nature of the progenitor star in the final stages of its life. The studyof the environment in the vicinity of the explosion site provides information on a possible relation between these unusual supernovaeand the properties of the galaxies hosting them.Results. Despite the lack of early-time observations, we provide reasonable evidence that SN 1999ga was probably a type II-linearsupernova that ejected a few solar masses of material, with a very small amount of radioactive elements of the order of 0.01 Mo.