VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion
Mattias Lazda, Kenzie Nimmo, Maria R. Drout, Benito Marcote, Jason W. T. Hessels, Eli Wiston, Raffaella Margutti, Omar Ould-Boukattine, Tanmoy Laskar, Jacco Vink, Ryan Chornock, James K. Leung, Deanne L. Coppejans, Dan Milisavljevic, Juan Mena-Parra, Dan Patnaude
arXiv:2601.06278v2 Announce Type: replace
Abstract: Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtained $gtrsim$ 6 years post-explosion have shown both (i) optical emission features consistent with a young PWN and (ii) a radio re-brightening. We present the results of our Very-Long-Baseline-Interferometric (VLBI) observations of SN 2012au performed between 8 to 13 years post core-collapse. Our VLBI observations reveal a luminous, steadily fading radio source that remains compact ($leq1.4times10^{17}~mathrm{cm}$) and stationary ($leq0.36c$) over the course of our campaign. Overall, we find that our VLBI measurements can be readily explained by a $sim$decade-old PWN, potentially explained by shock interaction with specific CSM geometries, and are unlikely to be explained by emission from an off-axis, relativistic jet. Assuming a PWN origin, our observations require that the initial spin-down luminosity of the central pulsar be between $10^{36}~mathrm{erg~s^{-1}}leqdot{E}_0leq {4times10^{42}}~mathrm{erg~s^{-1}}$ and radio efficiency factor be $eta_mathrm{R}geq {3times10^{-7}}$ (both quoted at the $ {99.7%}$ confidence interval). These results are consistent with independent inferences obtained using optical spectroscopy of SN 2012au, alongside inferences of known Galactic systems. If a PWN origin is confirmed, SN 2012au would represent the first extragalactic PWN emerging from a modern day SN, providing a novel opportunity to study the formation properties of a decade-old pulsar.arXiv:2601.06278v2 Announce Type: replace
Abstract: Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtained $gtrsim$ 6 years post-explosion have shown both (i) optical emission features consistent with a young PWN and (ii) a radio re-brightening. We present the results of our Very-Long-Baseline-Interferometric (VLBI) observations of SN 2012au performed between 8 to 13 years post core-collapse. Our VLBI observations reveal a luminous, steadily fading radio source that remains compact ($leq1.4times10^{17}~mathrm{cm}$) and stationary ($leq0.36c$) over the course of our campaign. Overall, we find that our VLBI measurements can be readily explained by a $sim$decade-old PWN, potentially explained by shock interaction with specific CSM geometries, and are unlikely to be explained by emission from an off-axis, relativistic jet. Assuming a PWN origin, our observations require that the initial spin-down luminosity of the central pulsar be between $10^{36}~mathrm{erg~s^{-1}}leqdot{E}_0leq {4times10^{42}}~mathrm{erg~s^{-1}}$ and radio efficiency factor be $eta_mathrm{R}geq {3times10^{-7}}$ (both quoted at the $ {99.7%}$ confidence interval). These results are consistent with independent inferences obtained using optical spectroscopy of SN 2012au, alongside inferences of known Galactic systems. If a PWN origin is confirmed, SN 2012au would represent the first extragalactic PWN emerging from a modern day SN, providing a novel opportunity to study the formation properties of a decade-old pulsar.