The Peculiar Transient At2018cow: A Possible Origin Of A Type Ibn/Iin Supernova

We present our photometric and spectroscopic observations of the peculiar transient AT2018cow. The multiband photometry covers from peak to similar to 70 days, and the spectroscopy ranges from 5 to similar to 50 days. The rapid rise (t(r) less than or similar to 2.9 days), high luminosity (M-V,M-peak similar to -20.8 mag), and fast decline after peak make AT2018cow stand out from any other optical transients, whereas we find that its light curves show a high resemblance to those of Type Ibn supernovae. Moreover, the spectral energy distribution remains at a high temperature of similar to 14,000 K at t > 15 days after discovery. The spectra are featureless in the first 10 days, while some broad emission lines due to H, He, C, and O emerge later, with velocity declining from similar to 14,000 to similar to 3000 km s(-1) at the end of our observations. Narrow and weak He I emission lines emerge in the spectra at t > 20 days after discovery. These emission lines are reminiscent of the features seen in interacting supernovae like the Type Ibn and IIn subclasses. We fit the bolometric light curves with a model of circumstellar interaction and radioactive decay of Ni-56 and find a good fit with ejecta mass M-ej similar to 3.16 M更多