VLA and ASKAP radio detection of SN 2016coi: ten years later

ATel #18154; A. Simongini (INAF-OAR; UniRoma2), A. Nucara (INAF-IAPS, UniRoma2), S. Lazarevic (WSU, CSIRO, AOB), T. Laskar (University of Utah), M. D. Filipovic (WSU), R. Brose (University of Potsdam), on behalf of the RISE collaboration
on 13 Nov 2026; 08:57 UT
Credential Certification: Andrea Simongini (andrea.simongini@inaf.it)

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We report radio detections of the Type Ic-BL supernova SN 2016coi in UGC 11868 (distance 15.6 Mpc), obtained as part of the Rebrightening in Interacting Supernova Emission (RISE) initiative.

Observations with the Karl G. Jansky Very Large Array (VLA) were carried out on 2026 October 30 under Regular Proposal VLA/26B-351 (PI: Dr. Tanmoy Laskar).

SN 2016coi was detected at 3.32 GHz with a preliminary flux density of 3.5 +/- 0.2 mJy and at 9.80 GHz with a preliminary flux density of 1.2 +/- 0.1 mJy. A preliminary fit assuming a power-law spectrum yields a spectral index of -0.96 +/- 0.09.

We also report a previously unreported detection from publicly available Australian SKA Pathfinder (ASKAP), obtained as part of the First Large Absorption Survey in HI (Allison et al. 2022, PASA, 39, e010) on 2025 December 24. We obtained a preliminary flux density of 8.06 +/- 0.50 at 0.856 GHz.

These observations extend the monitoring of the radio re-brightening of SN 2016coi, previously reported by Rose et al. 2025 (ATel #17533). The last reported detection was on December 1, 2024, with a flux density of 3.13 +/- 0.34 mJy at 1.37 GHz.

These observations demonstrate that SN 2016coi remains a luminous radio source ten years after its discovery and that it is evolving on relatively short timescales.

This ATel makes use of the following VLA data: VLA/26B-351. The National Radio Astronomy Observatory and Green Bank Observatory are facilities of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc. ASKAP data are obtained from Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. We acknowledge the Wajarri Yamaji People as the Traditional Owners and native title holders of the Observatory site. CSIRO 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.