Optical photometry and spectroscopy of the low-luminosity, broad-lined Ic supernova iPTF15dld

TL;DR

This study presents optical observations of the low-luminosity, broad-lined Type Ic supernova iPTF15dld, revealing a complex behavior with spectral features similar to energetic SNe Ic but light curve properties akin to low-luminosity SNe Ic.

Contribution

It provides detailed spectroscopic and photometric analysis of iPTF15dld, highlighting its unique combination of spectral broad lines and low luminosity, and estimates its progenitor and explosion parameters.

Findings

Spectra show broad absorption lines typical of energetic SNe Ic.

Light curve resembles low-luminosity, narrow-lined SNe Ic.

Estimated progenitor mass of 20-25 Msun, Ni56 mass of 0.1-0.2 Msun.

Abstract

Core-collapse stripped-envelope supernova (SN) explosions reflect the diversity of physical parameters and evolutionary paths of their massive star progenitors. We have observed the type Ic SN iPTF15dld (z = 0.047), reported by the Palomar Transient Factory. Spectra were taken starting 20 rest-frame days after maximum luminosity and are affected by a young stellar population background. Broad spectral absorption lines associated with the SN are detected over the continuum, similar to those measured for broad-lined, highly energetic SNe Ic. The light curve and maximum luminosity are instead more similar to those of low luminosity, narrow-lined Ic SNe. This suggests a behavior whereby certain highly-stripped-envelope SNe do not produce a large amount of Ni56, but the explosion is sufficiently energetic that a large fraction of the ejecta is accelerated to higher-than-usual velocities. We estimate SN iPTF15dld had a main sequence progenitor of 20-25 Msun, produced a Ni56 mass of ~0.1-0.2 Msun, had an ejecta mass of [2-10] Msun, and a kinetic energy of [1-18] e51 erg.