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e-MERLIN detection of SN2017eaw in NGC6946

ATel #10472; Megan Argo (UCLan), Miguel Perez Torres (IAA-CSIC, Granada), Rob Beswick (Manchester), Nick Wrigley (Manchester)
on 7 Jun 2017; 07:42 UT
Credential Certification: Megan Argo (megan.argo@gmail.com)

Subjects: Radio, Supernovae

Since our previously-reported non-detection (ATel #10421), we have continued to observe SN2017eaw in NGC6946 with e-MERLIN at 5.1 GHz. In each observation, the target was observed in phase-referencing mode with 2022+6136 as the phase calibrator, 1331+305 as the flux calibrator, and 1407+284 as the bandpass calibrator.

We detect an unresolved radio source at a position of RA=20h34m44.2370s Dec=+60d11'35.911" with an uncertainty of ±0.001 arcseconds in each coordinate, within 0.1 arcseconds of the supernova position reported in ATel #10381. An image of our detection can be found here: http://www.jb.man.ac.uk/~mkargo/SN2017eaw_eMERLIN_20170601.png The supernova is clearly detected at >5sigma in each epoch. We find that the 5.1 GHz emission from SN2017eaw is increasing. Details of our observations are:

Date | time on-target | number of antennas | flux density | rms
May 29.55 - May 30.33 | 11.7 hours | 3 antennas | 280 μJy | 25 μJy/beam
May 30.81 - May 31.35 | 8.7 hours | 4 antennas | 350 μJy | 51 μJy/beam
June 1.71 - June 2.33 | 9.0 hours | 5 antennas | 427 μJy | 23 μJy/beam

At a distance of 5.86±0.76Mpc (Bose & Kumar 2014), this gives a current 5.1-GHz monochromatic luminosity of 1.7x1025 erg/s/Hz. If this is the peak of the radio light curve, this puts SN2017eaw at the lower end of the luminosity distribution for core collapse supernovae. Given that previous radio-bright type IIP supernovae have taken ∼1 month to reach peak luminosity at 5 GHz, we are continuing to monitor this object.

We thank the e-MERLIN director for granting our DDT request, and the operations team for carrying out these observations.