ASKAP radio re-brightening of SN 2016coi

ATel #17533; K. Rose (U. Sydney, CSIRO), S. Ryder (Macquarie U.), and D. Kaplan (UWM) on behalf of the VAST collaboration
on 9 Dec 2025; 05:42 UT
Credential Certification: Kovi Rose (kovirose@gmail.com)

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SN 2016coi is a Type Ic-BL supernova (SN) that displayed late-time variability in its radio lightcurve (Rose et al. 2024). Here we report new radio observations with the Australian SKA Pathfinder (ASKAP) showing the onset of a new re-brightening event for SN 2016coi unrelated to the previous variability.

We inspected the publicly available ASKAP observations and obtained the following previously unreported Stokes I (S_I) flux densities

Date [UTC]	S_I [mJy]	Freq. [MHz]	Len. [min]	Survey
2023 Dec 29.34	1.45 +/- 0.28	944	15	RACS-low
2024 Dec 1.42	3.13 +/- 0.34	1368	15	RACS-mid

The quoted uncertainties include the systematic flux scale uncertainty of approximately 6% and the RMS in quadrature with the fitted error. We consider the measurements with a signal-to-noise ratio (SNR) greater than 5 times the RMS to be significant detections.

The observations used are from the Rapid ASKAP Continuum Survey (RACS-low; McConnell et al. 2020, RACS-mid; Duchesne et al. 2023). All observations were conducted with a bandwidth of 288 MHz.
The full ASKAP lightcurve is available here: https://drive.google.com/file/d/13HZeDAW4INRQB3mr4I_DTfZuBhKDsgZ6/view?usp=sharing
We encourage further multi-wavelength observations of this source.

This scientific work uses data obtained from Inyarrimanha Ilgari Bundara / the CSIRO's Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamaji People as the Traditional Owners and native title holders of the Observatory site. CSIRO's ASKAP radio telescope is part of the Australia Telescope National Facility (https://ror.org/05qajvd42 ). Operation of ASKAP is funded by the Australian Government with support from the National Collaborative Research Infrastructure Strategy. ASKAP uses the resources of the Pawsey Supercomputing Research Centre. Establishment of ASKAP, Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory and the Pawsey Supercomputing Research Centre are initiatives of the Australian Government, with support from the Government of Western Australia and the Science and Industry Endowment Fund. Archived data can be obtained through the CSIRO ASKAP Science Data Archive, CASDA ( http://data.csiro.au ).

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