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

Abstract

We present a multiband 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 an SN at only +34 days past the epoch of the B-band maximum. Additional HST images extending through +578 days cover the evolution of LE1 taking the form of a ring, while images taken on +1991 days reveal not only LE1 but also segments of a new inner LE ring (LE2) as well as two additional outer LE rings (LE3 and 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 farther 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.