ASASSN-14dq: A fast-declining type II-P Supernova in a low-luminosity host galaxy

TL;DR

This study presents detailed photometric and spectroscopic analysis of the fast-declining type II-P supernova ASASSN-14dq, highlighting its unique properties, low-metallicity environment, and evidence of ejecta-CSM interaction, contributing to understanding transitional supernovae.

Contribution

It provides the first comprehensive analysis of ASASSN-14dq, including its light curve, spectral features, progenitor characteristics, and evidence of CSM interaction, expanding knowledge of fast-declining type II-P supernovae.

Findings

ASASSN-14dq has a plateau duration of ~90 days and a higher decline rate than typical type II-P SNe.

Estimated $^{56}$Ni mass of ~0.029 M$_{igodot}$, slightly lower than expected for luminous type II-P SNe.

Evidence of ejecta interaction with circumstellar material through spectral features.

Abstract

Optical broadband (UBVRI) photometric and low-resolution spectroscopic observations of the type II-P supernova (SN) ASASSN-14dq are presented. ASASSN-14dq exploded in a low-luminosity/metallicity host galaxy UGC 11860, the signatures of which are present as weak iron lines in the photospheric phase spectra. The SN has a plateau duration of $\sim\,$90 d, with a plateau decline rate of 1.38 $\rm mag\ (100 d)^{-1}$ in V-band which is higher than most type II-P SNe. ASASSN-14dq is a luminous type II-P SN with a peak $V$-band absolute magnitude of -17.7$\,\pm\,$0.2 mag. The light curve of ASASSN-14dq indicates it to be a fast-declining type II-P SN, making it a transitional event between the type II-P and II-L SNe. The empirical relation between the steepness parameter and $\rm ^{56}Ni$ mass for type II SNe was rebuilt with the help of well-sampled light curves from the literature. A $\rm ^{56}Ni$ mass of $\sim\,$0.029 M$_{\odot}$ was estimated for ASASSN-14dq, which is slightly lower than the expected $\rm ^{56}Ni$ mass for a luminous type II-P SN. Using analytical light curve modelling, a progenitor radius of $\rm \sim3.6\times10^{13}$ cm, an ejecta mass of $\rm \sim10\ M_{\odot}$ and a total energy of $\rm \sim\,1.8\times 10^{51}$ ergs was estimated for this event. The photospheric velocity evolution of ASASSN-14dq resembles a type II-P SN, but the Balmer features (H$\alpha$ and H$\beta$) show relatively slow velocity evolution. The high-velocity H$\alpha$ feature in the plateau phase, the asymmetric H$\alpha$ emission line profile in the nebular phase and the inferred outburst parameters indicate an interaction of the SN ejecta with the circumstellar material (CSM).