TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4995 SUBJECT: OT 060420: CONCAM detection of a candidate new magnitude 5 optical DATE: 06/04/21 23:06:32 GMT FROM: Robert Nemiroff at Michigan Tech. R. J. Nemiroff and L. Shamir (Michigan Tech) report on behalf of the Night Sky Live CONCAM Project A magnitude 5 (five) optical transient (OT) of unknown origin appears on three successive frames from the Cerro Pachon CONCAM in Chile and concurrently on two successive frames from the Canary Island CONCAM in Spain. We estimate the broadband CONCAM unfiltered CCD magnitude at about 4.5 at its brightest. The approximate location of the transient is RA: 13 38 Dec: -12 25 with an accuracy of about 0.5 degrees. The times and brightness estimates (visually estimated and assumed accurate to about one magnitude) for the optical transient are: UT frame start: 00h 19m 43s Estimated magnitude: 5.0 Exposure: 180 sec CONCAM location: Cerro Pachon, Chile JPG image: http://nightskylive.net/cp/cp060420/cp060420ut001943p.jpg FITS image: http://nightskylive.net/cp/cp060420/cp060420ut001943p.fits X,Y location of OT on FITS image: (182, 514) UT frame start: 00h 23m 39s Estimated magnitude: 4.5 Exposure: 180 sec CONCAM location: Cerro Pachon, Chile JPG image: http://nightskylive.net/cp/cp060420/cp060420ut002339p.jpg FITS image: http://nightskylive.net/cp/cp060420/cp060420ut002339p.fits X,Y location of OT on FITS image: (187, 518) UT frame start: 00h 27m 36s Estimated magnitude: 5.0 Exposure: 180 sec CONCAM location: Cerro Pachon, Chile JPG image: http://nightskylive.net/cp/cp060420/cp060420ut002736p.jpg FITS image: http://nightskylive.net/cp/cp060420/cp060420ut002736p.fits X,Y location of OT on FITS image: (190, 520) UT frame start: 00h 19m 43s Estimated magnitude: 5.0 Exposure: 180 sec CONCAM location: Canary Islands, Spain JPG image: http://nightskylive.net/ci/ci060420/ci060420ut001943p.jpg FITS image: http://nightskylive.net/ci/ci060420/ci060420ut001943p.fits X,Y location of OT on FITS image: (429, 258) UT frame start: 00h 23m 41s Estimated magnitude: 4.5 Exposure: 180 sec CONCAM location: Canary Islands, Spain JPG image: http://nightskylive.net/ci/ci060420/ci060420ut002341p.jpg FITS image: http://nightskylive.net/ci/ci060420/ci060420ut002341p.fits X,Y location of OT on FITS image: (435, 257) The quality of the Canary Island CONCAM frames is marginal but, we believe, good enough to bolster the OT interpretation. This is the first time the Night Sky Live / CONCAM project is reporting such a transient and so we do advise caution about its interpretation as an astronomical source. However, the Night Sky Live project has had CONCAMs running since mid-2000 and has never before had cause to report any brief optical transient like this: this OT is seen on more than one frame, by more than one CONCAM, and appears to rotate with the sky. The OT was found initially by data mining software. Given the approximate 10,000 kilometer distance between the two CONCAMs, the lack of obvious parallax of the OT yields a minimum OT distance estimate of about 300,000 kilometers. All numbers and estimates are preliminary at this time. Future observations attempting to discern the nature of the OT 060420 are encouraged. This message may be cited.