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Main Authors: Sfaradi, Itai, Margutti, Raffaella, Chornock, Ryan, Nayana, A. J., Wiston, Eli, De Colle, Fabio, Clarke, Tracy E., Peters, Wendy M., Beniamini, Paz, Lu, Wenbin, Duran, Rodolfo Barniol, Bietenholz, Michael, Christy, Collin T., Coppejans, Deanne L., Drout, Maria R., Ibrahimzade, Dina, Michalowski, Michal J., Milisavljevic, Dan, Omand, Conor M. B., Wang, Yihan, Alexander, Kate D., Badenes, Carles, Bright, Joe, Granot, Jonathan, Hammerstein, Erica, Jacobson-Galan, Wynn V., LeBaron, Natalie, Murase, Kohta, Rameshan, Gitika, Sears, Huei, Stroh, Michael, Terreran, Giacomo
Format: Preprint
Published: 2026
Subjects:
High Energy Astrophysical Phenomena
Online Access:https://arxiv.org/abs/2605.16495
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Table of Contents:
  • We present late-time ($δt > 3000$ d) optical (Keck), X-ray (Chandra and NuSTAR), and radio (VLA, ALMA, and the uGMRT) observations of the Type Ic-BL SN 2012ap. Previous studies of this SN suggested that it stands out as a key example of a weak engine-driven explosion due to the lack of gamma-ray burst detection and a mildly relativistic ejecta. Recently, radio sky surveys revealed the rebrightening of the radio emission from this SN, highlighting the possibilities of a density enhancement at large radii or the existence of an off-axis relativistic jet. While the late-time optical spectra does not exhibit the broad emission lines seen in other interacting SNe, our analysis of the broadband radio and X-ray emission implies that both scenarios are plausible. If a density enhancement is responsible for the radio rebrightening, it has to result from a change in the mass-loss rate and/or wind velocity, possibly due to the transition of the progenitor from a red supergiant to a Wolf-Rayet star. If the late-time radio component is a result of an off-axis relativistic jet, we find that an energetic narrow jet viewed at $θ_{\rm obs} \geq 80^{\circ}$ is needed. In this scenario, SN 2012ap is not a result of a weak engine-driven explosion, and, instead, it is similar to other GRBs. However, radio rebrightenings of Type Ic-BL SNe are not enough on their own to determine the existence of off-axis jets and our planned VLBA observation will help reveal the true nature of this SN.

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