Optical and spectral observations and hydrodynamic modelling of Type IIb Supernova 2017gpn

TL;DR

This study presents detailed optical and spectral observations of Supernova 2017gpn, modeled with hydrodynamics to understand its explosion parameters and progenitor, challenging existing theories about Type IIb supernova origins.

Contribution

It provides the first combined observational and hydrodynamic modeling analysis of SN 2017gpn, including its unique location far from its host galaxy center.

Findings

Best-fit explosion model with 3.5 Msun progenitor and 50 Rsun radius

Explosion energy of 1.2 x 10^51 erg and 0.11 Msun of radioactive nickel

SN 2017gpn located 21 kpc from host galaxy center, challenging progenitor theories

Abstract

In this work we present the photometric and spectroscopic observations of Type IIb Supernova 2017gpn. This supernova was discovered in the error-box of LIGO/Virgo G299232 gravitational-wave event. We obtained the light curves in B and R passbands and modelled them numerically using the one-dimensional radiation hydrocode STELLA. The best-fit model has the following parameters: the pre-SN star mass and the radius are 3.5 Msun and 50 Rsun, respectively; the explosion energy is Eexp = 1.2 * 10^51 erg; the mass of radioactive nickel is M56Ni =0.11 Msun, which is totally mixed through the ejecta, the mass of the hydrogen envelope 0.06 Msun. Moreover, SN 2017gpn is a confirmed SN IIb that is located at the farthest distance from the center of its host galaxy NGC 1343 (i.e. the projected distance is about 21 kpc). This challenges the scenario of the origin of Type IIb Supernovae from massive stars.