Luminous Late-time Radio Emission from Supernovae Detected by the Karl G. Jansky Very Large Array Sky Survey (VLASS)
Abstract
We present a population of 19 radio-luminous supernovae (SNe) with emission reaching L ν ~ 1026-1029 erg s-1 Hz-1 in the first epoch of the Very Large Array Sky Survey (VLASS) at 2-4 GHz. Our sample includes one long gamma-ray burst, SN 2017iuk/GRB 171205A, and 18 core-collapse SNe detected at ≈1-60 yr after explosion. No thermonuclear explosion shows evidence for bright radio emission, and hydrogen-poor progenitors dominate the subsample of core-collapse events with spectroscopic classification at the time of explosion (79%). We interpret these findings in the context of the expected radio emission from the forward shock interaction with the circumstellar medium (CSM). We conclude that these observations require a departure from the single wind-like density profile (i.e., ρ CSM ∝ r -2) that is expected around massive stars and/or from a spherical Newtonian shock. Viable alternatives include the shock interaction with a detached, dense shell of CSM formed by a large effective progenitor mass-loss rate, $\dot{M}\sim {10}^{-4}\mbox{--}{10}^{-1}\,{M}_{\odot }$ Ṁ~10-4-10-1M⊙ yr-1 (for an assumed wind velocity of 1000 km s-1); emission from an off-axis relativistic jet entering our line of sight; or the emergence of emission from a newly born pulsar-wind nebula. The relativistic SN 2012ap that is detected 5.7 and 8.5 yr after explosion with L ν ~ 1028 erg s-1 Hz-1 might constitute the first detections of an off-axis jet+cocoon system in a massive star. However, none of the VLASS SNe with archival data points are consistent with our model off-axis jet light curves. Future multiwavelength observations will distinguish among these scenarios. Our VLASS source catalogs, which were used to perform the VLASS cross-matching, are publicly available at https://doi.org/10.5281/zenodo.4895112.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2021
- DOI:
- 10.3847/2041-8213/ac375e
- arXiv:
- arXiv:2106.09737
- Bibcode:
- 2021ApJ...923L..24S
- Keywords:
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- 304;
- 2008;
- 1464;
- 1766;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Published on December 21, 2021 Comments are welcome 17 pages, 4 figures, 1 table