[vsnet-grb-info 3161] OT 060420: Likely Not a New Cosmic Transient
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Mon Apr 24 05:06:25 JST 2006
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. <nemiroff at mtu.edu>
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.
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