[vsnet-grb-info 2948] Brightening of the Optical Counterpart of the Possible GRB 060218

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4785
SUBJECT: Brightening of the Optical Counterpart of the Possible GRB 060218
DATE:    06/02/19 06:07:32 GMT
FROM:    Frank Marshall at GSFC  <marshall at milkyway.gsfc.nasa.gov>

F. Marshall (GSFC), S. Immler (GSFC/USRA) and G. Cusumano (IASF-Pa INAF)
report on behalf of the Swift team:

Continuing UVOT observations of the possible GRB 060218 show that
the candidate optical afterglow reported by Cusumano et al. (GCN 4775)
and Marshall et al. (GCN 4779) has brightened by a factor of about 5
in the 10 hours since the BAT trigger. Consequently, this source is unlikely
to be the optical afterglow of a GRB. This brightening, the extended emission
detected with BAT, and the possible BAT detection a month earlier
(Barbier et al. GCN 4780) suggest that the UVOT source is the optical
counterpart of a hard X-ray transient.