The Rise and Peak of the Luminous Type IIn SN 2017hcc/ATLAS17lsn from ASAS-SN and Swift UVOT Data

We present observations of the rise and peak of the Type IIn supernova SN 2017hcc/ATLAS17lsn obtained by the All-Sky Automated Survey for Supernovae (ASAS-SN) and Swift UVOT. The light curve of SN 2017hcc/ATLAS17lsn peaks at $Vsimeq 13.7$ mag, which from the estimated redshift of the host galaxy ($z=0.0168$, $Dsimeq 73$ Mpc) implies an absolute peak magnitude $M_{V,peak} simeq -20.7$ mag. The near-UV to optical spectral energy distribution of SN 2017hcc/ATLAS17lsn from Swift UVOT is consistent with a hot, but cooling blackbody with $rm T_{bb}simeq 16500$ K on Oct. 28.4 and $rm T_{bb} simeq 11700$ K on Nov. 19.6. The estimated peak bolometric luminosity $L_{bol, peak}simeq 1.3times 10^{44}$ erg s$^{-1}$ makes SN2017hcc/ATLAS17lsn one of the most luminous Type IIn supernovae studied to date. From the bolometric light curve we constrain the risetime to be $sim 27$ days and the total radiated energy of the event to date is $4times 10^{50}$ erg.