//////////////////////////////////////////////////////////////////////// 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4997 SUBJECT: No OT 060420 in MASCOT images DATE: 06/04/22 15:45:00 GMT FROM: Alain Smette at ESO/Chile A. Smette (ESO Chile) reports: The Mini All-Sky Cloud Observation Tool (MASCOT) located at ESO's Very Large Telescope Observatory, Cerro Paranal, Chile, (http://www.eso.org/instruments/mascot/index.html) obtained 90 s images simultaneously to the CONCAM images reported in GCN 4995. Comparison with previous MASCOT images indicates that there is no optical transient at the reported location of the proposed OT060420 in images taken between 2006-04-20T00:15 and 2006-04-20T00:36 UT. Although conditions were cloudy, limiting magnitudes are similar to the CONCAM images. MASCOT images are available through the ESO archive: http://archive.eso.org/eso/eso_archive_main.html //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4998 SUBJECT: OT 060420: Likely Not a New Cosmic Transient DATE: 06/04/23 20:04:08 GMT FROM: Robert Nemiroff at Michigan Tech. 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.