Tight constraints on the mass-loss rate of the Type Ia SN 2016coj with e-MERLIN

ATel #10168; M. Perez-Torres (IAA-CSIC), P. Lundqvist, E. Kundu (Stockholm), J. Moldon (JBCA), C.-I. Bjornsson, C. Fransson (Stockholm), S. Ryder (AAO)
on 14 Mar 2017; 12:47 UT
Credential Certification: Miguel A. Perez-Torres (torres@iaa.es)

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We report e-MERLIN radio observations of the Type Ia supernova 2016coj, which was discovered on 28.18 May 2016 (MJD 57536.18) in the nearby (D=20.1 Mpc) galaxy NGC 4125 (cf. ATel #9095). Our observations were carried out on 3-4 June 2016 (MJD 57542.92) with a duration of 12 hr, one week after the SN discovery and about one week before reaching its V-band maximum. The radio telescopes that participated in the observations included five e-MERLIN antennas (Cambridge, Pickmere, Darnhall, Knockin, and Defford). The array observed at a central frequency of 1.51 GHz and used a total bandwidth of 512 MHz, which resulted in a synthesized Gaussian beam of (0.13 x 0.12) sq. arcseconds. We centered our observations at the position of the optical discovery ( (J2000.0) coordinates RA = 12:08:06.80, Dec = +65:10:37.9, ATel #9095) and imaged a (16x16) sq. arcsecond region centered at this position. We found no evidence of radio emission in the region surrounding SN2016coj down to a 3-sigma limit of 126 microJy/beam, which corresponds to an upper limit of the monochromatic 5.0 GHz luminosity of 6.1e25 erg/s/Hz (3-sigma). Assuming the models in Kundu et al. (submitted to The Astrophysical Journal) and Perez-Torres et al. (2014, ApJ, 792, 38) for the radio emission of Type Ia SNe, our observations place a very stringent upper limit to the wind mass loss rate of the supernova progenitor of 2.3e-8 solar masses per year (3-sigma) for an assumed wind speed of 100 km/s. For typical parameters used in this model, our data are more constraining than the JVLA data in ATel #9193. We thank the e-MERLIN staff for supporting our ToO program in search for radio emission from Type Ia supernovae, aimed at unveiling their progenitor scenarios.