Radio Detection of SN 2014bc in NGC 4258 with eMERLIN

ATel #6270; M. Argo (JBCA, Manchester), M. Perez-Torres (IAA-CSIC and CEFCA, Spain), A. Alberdi (IAA-CSIC), R. Beswick (JBCA, Manchester), J. Conway (OSO, Onsala), N. Elias-Rosa (INAF, Padova), R. Herrero-Illana (IAA-CSIC, Granada), R. Kotak (Queen's Univ. Belfast), P. Lundqvist (Stockholms Observatory), S. Mattila (Univ. of Turku), J. Marcaide (Univ. de Valencia), T. Muxlow (JBCA, Manchester), I. Marti-Vidal (OSO, Onsala), N. Ramirez-Olivencia (IAA-CSIC, Granada), C. Romero-Canizales (IA-PUC/MAS, Chile), C. Stockdale (Marquette University), E. Varenius (OSO, Onsala).
on 25 Jun 2014; 14:55 UT
Credential Certification: Miguel A. Perez-Torres (torres@iaa.es)

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We report the first detection at radio wavelengths of the type II SN 2014bc, using the electronic Multi-Element Radio Linked Interferometer Network (eMERLIN).SN 2014bc, initially dubbed PS1-14xz (also PSN J12185771+4718113) was discovered near (~100 pc) the core of NGC4258 (Messier 106; D=7.6 Mpc) by Smartt et al. (ATel #6156). KAIT unfiltered imaging by Zheng and Fillipenko (ATel #6159) showed the light curve of PS1-14xz to be consistent with a Type II-P SN, and a spectrogram confirmed the transient to be a Type II SN (Smartt et al. and Ochner et al. CBET 3877). The discovery images were taken on 2014 May 19.25 UT with the Pan-STARRS1 telescope. Unfiltered CCD images on 2014 May 9.98 did not detect the SN down to a limiting magnitude of 18.5 (very faint, pre-discovery, CBET 3877).

We observed SN 2014bc at a frequency of 1.51 GHz on 2014 May 23 with eMERLIN, using a total bandwidth of 512 MHz. The resulting synthesized Gaussian beam was of (0.15 x 0.13) sq. arcseconds. We centered our observations at the position of the optical discovery (RA(J2000.0)=12:18:57.71 and DEC(J2000.0)=47:18:11.3) and imaged a (113 x 113) sq. arcsecond region. We detected SN 2014bc with a peak flux density of 1.165 mJy/b at the following position: RA(J2000.0)=12:18:57.5034; DEC(J2000.0)=47:18:11.286. The off-source r.m.s. of the image was of 0.035 mJy/b. The above radio brightness corresponds to a monochromatic 1.51 GHz luminosity of (8.00 +/- 0.25)*1e25 erg/s/Hz. This value is typical of Type II-P SNe close to its peak radio luminosity. However, since our observations were taken when the SN was less than about 13 days old, the detection at 1.51 GHz would imply a very fast evolution for SN 2014bc, if it is indeed a type II-P SN (see, e.g. Fig. 4 in Romero-Canizales et. al 2014, MNRAS, 440, 1067).

Further observations of this nearby SN at radio and other wavelengths are planned to shed light on the CCSN type of SN 2014bc.

We thank the eMERLIN staff for supporting our ToO program on nearby core-collapse supernovae (Project code CY1204; PI: Perez-Torres).