SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared

TL;DR

This paper provides a comprehensive one-year observational study of the low-luminosity type II-plateau supernova SN 2005cs in M51, including optical and near-infrared data, bolometric light curve, and modeling results.

Contribution

It offers the most detailed dataset for a low-luminosity, 56Ni-poor type II supernova, including optical and near-infrared spectra, light curves, and bolometric analysis, along with modeling of explosion parameters.

Findings

SN 2005cs had low expansion velocity (~1000 km/s).

The supernova's bolometric light curve was constructed for the first time for this class.

Estimated 56Ni mass is about 0.003 solar masses.

Abstract

We present the results of the one year long observational campaign of the type II-plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool Galaxy). This extensive dataset makes SN 2005cs the best observed low-luminosity, 56Ni-poor type II-plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km/s) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 days after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 days. In addition to optical observations, we also present near-infrared light curves that (together with already published UV observations) allow us to construct for the first time a reliable bolometric light curve for an object of this class. Finally, comparing the observed data with those derived from a semi-analytic model, we infer for SN 2005cs a 56Ni mass of about 0.003 solar masses, a total ejected mass of 8-13 solar masses and an explosion energy of about 3 x 10^50 erg.