GCN Circular 4998
R. J. Nemiroff and L. Shamir report on behalf of the Night Sky Live / CONCAM project We verify the report in GCN 4997 that OT 060420 does not appear on MASCOT frames. Because the OT was near MASCOT's limiting brightness and to be conservative, we then co-added MASCOT frames taken around the time of candidate OT 060420 in an attempt to rival the sensitivity of the Cerro Pachon CONCAM images. Given an assumption of equal bandpass, detection of OT 060420 was expected but not found. Inspection of the Cerro Pachon CONCAM images also show somewhat unusual OT PSFs. More detailed analyses of the Canary Island CONCAM images showed them to be generally less reliable than we originally expected. Therefore, it is now our best guess that the cause for candidate OT 060420 is a rare series of similar, extended, precisely-placed, time-consecutive cosmic-ray hits. We no longer encourage follow-up observations. For interest, here is a short movie of the candidate transient as it appeared on the Cerro Pachon CONCAM frames: http://nightskylive.net/temp/movie2_cp060420.gif We are grateful to A. Smette and the MASCOT team for making their images available.