We have identified pre-discovery imaging of the probable classical nova ASASSN-18fv by Evryscope-South, an array of 6-cm telescopes continuously monitoring 8000 square degrees of sky at 2-minute cadence from CTIO, Chile.
The transient is not detected at UT 2018-03-16.0316 with an upper-limit of 11.9 +/- 0.1 mag (g’) set by the blended flux from the nearby bright star (cataloged at V~5.2 in Tycho-2).
Beginning at UT 2018-03-16.227, we detect a new source at 10.21 +/- 0.05 mag (g’), calibrated using 1817 nearby stars from the AAVSO Photometric All-Sky Survey DR9 catalog (Henden 2010) with a median residual of 0.04 mag. The rate of brightening (> 0.8 mag (g’) / hour) is consistent with the V-band measurement by ASAS-SN 2.2 hours later at UT 2018-03-16.32 (ATel #11454). The transient has since been detected in >1200 Evryscope epochs.
Pre- and post- detection images are below. A light curve will be posted here when available.
We gratefully acknowledge the support of the National Science Foundation through grants ATI-1407589, CAREER-1555175, and DGE-1144081, and the Research Corporation Scialog Program. Evryscope is supported jointly by the University of North Carolina at Chapel Hill and San Diego State University.