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

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 ∼90 d, with a plateau decline rate of 1.38 mag (100d)−1 in the 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 ±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 Type II-P and II-L SNe. The empirical relation linking the steepness parameter and 56Ni mass for Type II SNe was rebuilt with the help of well-sampled light curves from the literature. The estimated 56Ni mass of ∼0.029 M⊙ for ASASSN-14dq is slightly lower for a luminous Type II-P SN. Using analytical light curve modelling, a progenitor radius of ∼3.6×1013 cm, an ejecta mass of ∼10 M⊙⁠, and total energy of ∼1.8×1051 erg were estimated for this event. The photospheric velocity evolution of ASASSN-14dq resembles that of a Type II-P SN, but the Balmer features (H α and H β) show relatively slow velocity evolution. The high-velocity H α feature in the plateau phase, the asymmetric H α emission line profile in the nebular phase, and the inferred outburst parameters indicate an interaction of the SN ejecta with the circumstellar material.