Sn 2008in - bridging the gap between normal and faint supernovae of type IIP

TL;DR

This paper presents detailed observations of SN 2008in, a Type IIP supernova, revealing it as a low-energy event with a relatively high nickel yield, bridging the gap between normal and faint Type IIP supernovae.

Contribution

It provides comprehensive photometric and spectroscopic analysis of SN 2008in, estimating key physical parameters and proposing a low-energy explosion model for a moderate-mass progenitor.

Findings

SN 2008in had a plateau duration of ~98 days.

Estimated Ni mass was ~0.015 solar masses.

Explosion energy was ~5.4×10^50 erg.

Abstract

We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M 61. Photometric data in the X-rays, ultraviolet and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ~ 98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. (2010) indicates that it is a less energetic event (~ 5$\times10^{50}$ erg). However, the light curve indicates that the production of radioactive $^{56}$Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of $A_V$ ~ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized Ni mass of ~ 0.015 $M_{\odot}$. Employing semi-analytical formulae (Litvinova & Nadezhin 1985), we derived a pre-SN radius of ~ 126$R_{\odot}$, an explosion energy of ~ 5.4$\times10^{50}$ erg and a total ejected mass of ~ 16.7$M_{\odot}$. The latter indicates that the zero age main-sequence mass of the progenitor did not exceed 20$M_{\odot}$. Considering the above properties of SN 2008in, and its occurrence in a region of sub-solar metallicity ([O/H] ~ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star.