Six years of luminous X-ray emission from the strongly interacting type-Ib SN 2014C captured by Chandra and NuSTAR

TL;DR

This study presents a comprehensive six-year X-ray observation of supernova SN 2014C, revealing unexpected hydrogen-rich material interaction that challenges existing models of hydrogen-poor progenitor evolution.

Contribution

It provides the first coordinated soft and hard X-ray data over six years, uncovering a dense shell of material and proposing new scenarios for progenitor star evolution.

Findings

Detection of a dense shell of 1-2 solar masses at 6×10^{16} cm

Observation of transition from type Ib to type IIn supernova

Challenging current models of hydrogen-poor progenitor evolution

Abstract

We present the first coordinated soft and hard 0.3-80 keV X-ray campaign of the extragalactic supernova SN 2014C in the first $\sim$2307 d of its evolution. SN 2014C initially appeared to be an ordinary type Ib explosion but evolved into a strongly-interacting hydrogen-rich type IIn SN over $\sim1 \rm{yr}$. We observed signatures of interaction with a dense medium across the X-ray spectrum, which revealed the presence of a $\sim 1-2 \rm{M}_{\odot}$ shell of material at $\sim6\times10^{16} \rm{cm}$ from the progenitor. This finding challenges current understanding of hydrogen-poor core-collapse progenitor evolution. Potential scenarios to interpret these observations include (i) the ejection of the hydrogen envelope by the progenitor star in the centuries prior to the explosion; (ii) interaction of the fast Wolf-Rayet (WR) star wind with the slow, dense wind of the Red Super Giant (RSG) phase, with an anomalously short WR phase.