ASKAP radio re-brightening of SN 2016coi and SN 2017hyh
ATel #17531; K. Rose (U. Sydney, CSIRO), S. Ryder (Macquarie U.), and D. Kaplan (UWM) on behalf of the VAST collaboration
on 9 Dec 2025; 05:35 UT
Credential Certification: Kovi Rose (kovirose@gmail.com)
Subjects: Radio, Supernovae, Transient
Referred to by ATel #: 17533
SN 2016coi is Type Ic-BL supernova (SN) that displayed late-time variability in its radio lightcurve (Rose et al. 2024). SN 2017hyh is a Type IIb SN, previously showing hints of radio re-brightening but not confirmed (Rose et al. 2024).
Here we report new radio detections of both SNe with the Australian SKA Pathfinder (ASKAP): The rise of a new re-brightening event for SN 2016coi unrelated to the previous variability; and the first confirmation of re-brightening in SN 2017hyh, with multiple events detected.
We inspected the publicly available ASKAP observations and obtained the following previously unreported Stokes I (S_I) flux densities
SN 2016coi:
| 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 |
SN 2017hyh:
| Date [UTC] |
S_I [mJy] |
Freq. [MHz] |
Len. [min] |
Survey |
| 2023 Jun 25.24 |
3.93 ± 0.38 |
888 |
12 |
ASKAP E&C |
| 2023 Jul 5.23 |
3.82 ± 0.40 |
888 |
12 |
VAST |
| 2023 Aug 29.97 |
4.56 ± 0.43 |
888 |
12 |
VAST |
| 2023 Nov 1.80 |
7.30 ± 0.61 |
888 |
12 |
VAST |
| 2023 Dec 28.73 |
7.30 ± 0.80 |
944 |
15 |
RACS-low |
| 2023 Dec 29.73 |
6.96 ± 0.51 |
944 |
14 |
RACS-low |
| 2024 Apr 25.36 |
5.16 ± 0.44 |
888 |
12 |
VAST |
| 2024 Jun 21.16 |
9.40 ± 0.67 |
888 |
12 |
VAST |
| 2024 Aug 21.99 |
10.01 ± 0.68 |
888 |
12 |
VAST |
| 2024 Oct 31.89 |
10.18 ± 1.83 |
1368 |
15 |
RACS-mid |
| 2024 Nov 6.87 |
6.21 ± 0.49 |
1368 |
15 |
RACS-mid |
| 2025 Feb 16.57 |
5.27 ± 0.44 |
888 |
12 |
VAST |
| 2025 Apr 13.37 |
6.55 ± 0.56 |
888 |
12 |
VAST |
| 2025 Jun 9.32 |
7.43 ± 0.53 |
888 |
12 |
VAST |
| 2025 Aug 20.11 |
8.28 ± 0.72 |
888 |
12 |
VAST |
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.
We find the average J2000 positions of:
SN 2016coi (R.A., Dec) = (329.7668 deg, 18.1860 deg) = (21h59m04.0s +18d11m09.6s)
SN 2017hyh: (R.A., Dec) = (107.6709 deg, 6.4614 deg) = (07h10m41.0s +06d27m41.0s)
with uncertainties of +/-2 arcsec in both R.A. and Dec.
The observations used are: Rapid ASKAP Continuum Survey (RACS-low; McConnell et al. 2020, RACS-mid; Duchesne et al. 2023), ASKAP Engineering & Commissioning (Harvey-Smith et al. 2023), and Variables and Slow Transients (VAST; Murphy et al. 2021). All observations were conducted with a bandwidth of 288 MHz.
The full ASKAP lightcurves are available here: https://drive.google.com/drive/folders/13i9Jlr4Yg0gicrr6hywdWnQbcSnF_9VX?usp=sharing
