Old and Bright: The Remarkable Radio Brightening of the Engine-driven SN 2012au Several Years after Explosion Signals the Birth of a Pulsar Wind Nebula
Year: 2026
Type: article
Abstract: We present the results from an extensive broadband (radio to X-rays) observing campaign of the engine-driven Type Ib SN 2012au in the first 13 yr of evolution. The early time ( δt ≤ 190 days) radio and X-ray evolution is well described by conventional models of a forward shock interacting with a wind-like circumstellar medium (CSM; ρ CSM ∝ r −2 ). However, starting at δt ≈ 6.7 yr, we detect a significant radio rebrightening. This late-time emission is dominated by a luminous component characterized by a broad and rapidly evolving spectral peak and a shallow optically thin spectral slope, F ν ∝ ν −0.31 ± 0.02 . These properties imply a compact emitting region ( R ≲ 10 16 cm) expanding at a remarkably slow velocity ( v s ≲ 500 km s −1 ) into a high-density environment ( n e ≥ 10 4 cm −3 ), accompanied by a hard electron power-law index p ≈ 1.6. No soft or hard X-ray emission is detected at any epoch, indicating that high-energy radiation is either strongly absorbed or intrinsically absent. In the context of aspherical shock–CSM interaction models, these observations imply extreme properties of the CSM (geometry, density, and total mass) that lack clear astrophysical motivation. Instead, we show that the emergence of radiation from a newborn pulsar wind nebula (PWN) naturally explains the radio spectral evolution and high-energy limits, where the emission is governed by the adiabatic expansion of a relic pair plasma. We conclude that SN 2012au represents the most compelling candidate for a young, newborn PWN discovered to date, a scenario that can be directly tested with pending very long baseline interferometry observations.
Source: The Astrophysical Journal
Authors: Eli Wiston, Raffaella Margutti, Nayana A. J., Brian D. Metzger, Kohta Murase, Dan Milisavljevic, Itai Sfaradi, Ryan Chornock, Deanne L. Coppejans, Joe Bright, Garrett K. Keating, Giacomo Terreran, Mattias Lazda, Maria R. Drout, Michael Stroh, Lauren Rhodes, Ben Margalit, Jonathan Granot, Fabio De Colle, Michael Bietenholz, Daichi Tsuna, Samantha Wu, Wenbin Lu, Tanmoy Laskar, Edo Berger, Mark A. Gurwell, Ramprasad Rao, Daniel Patnaude, Collin T. Christy
Institutions: University of California System, Columbia University, Pennsylvania State University, Yukawa Institute for Theoretical Physics, Purdue University West Lafayette, University of Warwick, University of Oxford, Center for Astrophysics Harvard & Smithsonian, Adler Planetarium, University of Toronto, National Radio Astronomy Observatory, Trottier Space Institute at McGill, McGill University, University of Minnesota, Open University of Israel, George Washington University, Universidad Nacional Autónoma de México, York University, Hartebeesthoek Radio Astronomy Observatory, Northwestern University, Carnegie Institution for Science, University of Utah, University of Arizona
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, National Radio Astronomy Observatory, Tata Institute of Fundamental Research, Canada Research Chairs, Academia Sinica, Korea Astronomy and Space Science Institute, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, National Astronomical Observatory of Japan, National Science and Technology Council, Centers for Disease Control and Prevention, Smithsonian Astrophysical Observatory, Natural Sciences and Engineering Research Council of Canada, Fonds de recherche du Québec – Nature et technologies, Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México, National Institutes of Natural Sciences
Awards: G4800341064, G5568448562, Collaborative Research: A Multi-Wavelength Observational and Theoretical Study of the Fastest Evolving Stellar Explosions, CAREER: A Holistic Study of Compact-Object Mergers across the Electromagnetic Spectrum, WoU-MMA: Collaborative Research: Advancing the SuperNova Early Warning System, G8100935542, Collaborative Research: Constraining Supernova Progenitor Systems and Explosion Mechanisms Through 3D Reconstruction of Supernova Remnants
OpenAlex ID: W7204443956