Luminous Late-time Radio Emission from Supernovae Detected by the Karl G. Jansky Very Large Array Sky Survey (VLASS). (arXiv:2106.09737v1 [astro-ph.HE])

Luminous Late-time Radio Emission from Supernovae Detected by the Karl G. Jansky Very Large Array Sky Survey (VLASS). (arXiv:2106.09737v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Stroh_M/0/1/0/all/0/1">M. C. Stroh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Terreran_G/0/1/0/all/0/1">G. Terreran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coppejans_D/0/1/0/all/0/1">D. L. Coppejans</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bright_J/0/1/0/all/0/1">J. S. Bright</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Margutti_R/0/1/0/all/0/1">R. Margutti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bietenholz_M/0/1/0/all/0/1">M. F. Bietenholz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Colle_F/0/1/0/all/0/1">F. De Colle</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+DeMarchi_L/0/1/0/all/0/1">L. DeMarchi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duran_R/0/1/0/all/0/1">R. Barniol Duran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milisavljevic_D/0/1/0/all/0/1">D. Milisavljevic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murase_K/0/1/0/all/0/1">K. Murase</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Paterson_K/0/1/0/all/0/1">K. Paterson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Williams_W/0/1/0/all/0/1">W. L. Williams</a>

We present a population of 20 radio-luminous supernovae (SNe) with emission
reaching $L_{nu}{sim}10^{26}-10^{29}rm{erg s^{-1} Hz^{-1}}$ 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/GRB171205A, and 19 core-collapse
SNe detected at $approx (1-60)$ years after explosion. No thermonuclear
explosion shows evidence for bright radio emission, and hydrogen-poor
progenitors dominate the sub-sample of core-collapse events with spectroscopic
classification at the time of explosion (73%). We interpret these findings into
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.,
$rho_{rm{CSM}}propto r^{-2}$) that is expected around massive stars and/or a
departure 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 $dot M sim (10^{-4}-10^{-1})$ M$_{odot}$
yr$^{-1}$ (for an assumed wind velocity of $1000,rm{km,s^{-1}}$); 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 years after explosion with $L_{nu}{sim}10^{28}$
erg s$^{-1}$ Hz$^{-1}$ might constitute the first detections of an off-axis
jet+cocoon system in a massive star. Future multi-wavelength 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.

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