$Hubble~Space~Telescope$ Reveals Spectacular Light Echoes Associated with the Stripped-envelope Supernova 2016adj in the Iconic Dust Lane of Centaurus A

TL;DR

This study documents the discovery and evolution of multiple light echoes from supernova 2016adj in Centaurus A using Hubble Space Telescope images, revealing complex dust structures in the supernova's environment.

Contribution

It provides the first detailed multi-epoch imaging of light echoes from a supernova in Centaurus A, revealing multiple dust sheets and their spatial configuration.

Findings

Multiple light echoes observed over 2000 days.

Dust sheets are clumpy with varying holes affecting light echo appearance.

Light echoes indicate complex dust geometry around the supernova.

Abstract

We present a multi-band sequence of $Hubble~Space~Telescope$ images documenting the emergence and evolution of multiple light echoes (LEs) linked to the stripped-envelope supernova (SN) 2016adj located in the central dust-lane of Centaurus A. Following point-spread function subtraction, we identify the earliest LE emission associated with a SN at only $+$34 days (d) past the epoch of $B$-band maximum. Additional HST images extending through $+$578 d cover the evolution of LE1 taking the form of a ring, while images taken on $+$1991 d reveals not only LE1, but also segments of a new inner LE ring (LE2) as well as two additional outer LE rings (LE3 & LE4). Adopting the single scattering formalism, the angular radii of the LEs suggest they originate from discrete dust sheets in the foreground of the SN. This information, combined with measurements of color and optical depth of the scattering surfaces, informs a scenario with multiple sheets of clumpy dust characterized by a varying degree of holes. In this case, the larger the LE's angular radii, the further in the foreground of the SN its dust sheet is located. However, an exception to this is LE2, which is formed by a dust sheet located in closer proximity to the SN than the dust sheets producing LE1, LE3, and LE4. The delayed appearance of LE2 can be attributed to its dust sheet having a significant hole along the line-of-sight between the SN and Earth.