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

TL;DR

This paper investigates the properties of the low-luminosity Type II-linear supernova SN 1999ga, providing insights into its explosion mechanics, progenitor star, and host galaxy environment despite limited early observations.

Contribution

It presents the first detailed analysis of a subluminous Type II-linear supernova, constraining its explosion energetics and progenitor characteristics.

Findings

SN 1999ga ejected a few solar masses of material

It contained about 0.01 solar masses of radioactive elements

The supernova was likely a low-luminosity Type II-linear event

Abstract

Type II-linear supernovae are thought to arise from progenitors that have lost most of their H envelope by the time of the explosion, 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. In this context, the discovery of a subluminous type II-linear event is even more interesting. We investigate the physical properties and characterise the explosion site of the type II SN 1999ga, which exploded in the nearby spiral galaxy NGC 2442. Spectroscopic and photometric observations of SN 1999ga allow us to constrain the energetics of the explosion and to estimate the mass of the ejected material, shedding light on the nature of the progenitor star in the final stages of its life. The study of the environment in the vicinity of the explosion site provides information on a possible relation between these unusual supernovae and the properties of the galaxies hosting them. Despite the lack of early-time observations, we provide reasonable evidence that SN 1999ga was probably a type II-linear supernova that ejected a few solar masses of material, with a very small amount of radioactive elements of the order of 0.01 solar masses.