Radio detection of the hydrogen-poor super-luminous supernova SN 2017ens at 3.6 years post explosion

ATel #14393; Deanne L. Coppejans (Northwestern U.), David Matthews (Northwestern U.), Raffaella Margutti (Northwestern U.), Giacomo Terreran (Northwestern U.), Edo Berger (Harvard U.), Tarraneh Eftetkhari (Harvard U.), Tanmoy Laskar (U. Bath), Matt Nicholl (U. Birmingham), Michael Bietenholz (SARAO/Hartrao and York U.), Kate D. Alexander (Northwestern U.), Wynn Jacobson-Galan (Northwestern U.), Peter K. Blanchard (Northwestern U.)
on 15 Feb 2021; 20:21 UT
Credential Certification: Deanne Coppejans (deanne.coppejans@gmail.com)

Tweet

We report the first radio detection of the supernova (SN) 2017ens. The object was initially spectroscopically classified as a hydrogen-poor, broad-line Ic SN. Unusually for this class though, the transient quickly reached a peak luminosity of -21.1 mag in g-band (Chen et al. 2018), more typical of super-luminous supernovae (SLSNe). This is the second hydrogen-poor SLSN detected at radio wavelengths (the first was iPTF10hgi, see Eftekhari et al. 2019). We observed SN 2017ens on 28 January 2021 with the NSF's Karl G. Jansky Very Large Array (VLA) with program VLA/20B-144 (PI: Matthews). We detected an unresolved radio source within one synthesized beamwidth of the optical position. The emission is optically thin at 6 GHz. Here we report the preliminary flux density:

 
Name | Date (UT) | Mean Obs Freq (GHz) | Bandwidth (GHz) | Flux density (microJy) | Uncertainty (microJy) | RA | Dec 
SN 2017ens | 2021 Jan 28 12:03:23 | 6.0 | 4.096 | 39 | 5 | 12:04:09.387 | -01:55:52.49 

We note that SN 2017ens was not detected in our earlier 6 GHz observations taken at ~2 months and ~5 months post explosion (VLA/17A-480, PI: Coppejans and VLA/17B-225, PI: Margutti). At these epochs we obtained 3-sigma upper-limits of 36 and 20 uJy/beam respectively. The brightening at radio wavelengths at 3.6 years post explosion may be produced by the interaction of the blastwave with a dense circumstellar environment. This is in agreement with optical observations of SN 2017ens that indicate that there is interaction with a dense hydrogen-rich circumstellar environment at this phase (Chen et al. 2018).

We are conducting further multi-band observations. We thank the VLA for scheduling these observations.