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Radio Detection of the Type IIb Supernova 2011cb in ESO 109-21

ATel #3370; S. D. Ryder (AAO), S. W. Amy (CSIRO), C. J. Stockdale (Marquette), S. Immler (NASA/GSFC), J. Stevens (CSIRO), K. W. Weiler (NRL)
on 23 May 2011; 04:06 UT
Credential Certification: Stuart Ryder (sdr@aao.gov.au)

Subjects: Radio, Supernovae

The Type IIb Supernova 2011cb (CBET #2711) in the galaxy PGC 69707 (ESO 109-021) has been observed with the Australia Telescope Compact Array (ATCA) + CABB 2 GHz backend system on 2011 May 5.7, 2011 May 13.7, and 2011 May 19.9 UT at frequencies of 9.0 and 5.5 GHz. In the first epoch we detected a radio source at a position consistent with that measured optically, and fluxes of 0.52+/-0.08 mJy and 0.73+/-0.05 mJy at 9.0 and 5.5 GHz, respectively. Measured fluxes at the second epoch were 0.38+/-0.10 mJy and 0.39+/-0.05 mJy, and at the third epoch 0.33+/-0.05 mJy and 0.39+/-0.03 mJy, at 9.0 and 5.5 GHz respectively. This indicates that within a week of maximum light as inferred from the optical spectra (CBET #2711) the supernova's radio emission at these frequencies had already peaked and entered the optically-thin decline phase. Monitoring at these and lower frequencies is continuing. We would like to extend our thanks to the ATCA staff for enabling these observations. The Australia Telescope Compact Array is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.