X-ray illumination of the ejecta of Supernova 1987A

TL;DR

This study tracks the 17-year optical light curve of SN 1987A's ejecta, revealing a transition from radioactive decay to X-ray powered emission, marking the shift from supernova to supernova remnant.

Contribution

It provides the first long-term optical light curve analysis showing the transition in energy sources powering the ejecta of SN 1987A.

Findings

Ejecta flux declined until 2001 due to radioactive decay of 44Ti.

Post-2001, flux increased due to X-ray illumination from circumstellar interaction.

The transition signifies the change from supernova to supernova remnant phase.

Abstract

We present the late-time optical light curve of the ejecta of SN 1987A measured from HST imaging observations spanning the past 17 years. We find that the flux from the ejecta declined up to around year 2001, powered by the radioactive decay of 44Ti. Then the flux started to increase, more than doubling by the end of 2009. We show that the increase is the result of energy deposited by X-rays produced in the interaction with the circumstellar medium. We suggest that the change of the dominant energy input to the ejecta, from internal to external, marks the transition from supernova to supernova remnant. The details of the observations and the modelling are described in the accompanying supplementary information.