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GCN Circular 3307

GRB 050421: Swift-UVOT observation
2005-04-21T17:36:02Z (19 years ago)
Alexander Blustin at MSSL-UCL <>
A. Blustin (MSSL), L. Barbier (GSFC), K. McGowan (MSSL),
P. Roming (PSU), M. De Pasquale (MSSL), S. T.  Holland (GSFC),
N. Gehrels (GSFC), K. Mason (MSSL), J. Nousek (PSU), on behalf
of the Swift UVOT team

Starting with the data taken ~245s after the BAT trigger (Barbier
et al., GCN 3296) we have co-added the early time data of GRB 050421
in each of the Ultra-Violet/Optical Telescope (UVOT) V, B and U
bands. The co-added images are made up of 9 x 10s exposures. No
source is detected within the revised XRT error circle (Godet et al.,
GCN 3301) in any of the bands; we estimate the five sigma magnitude
upper limits from the co-added images to be:

Filter Upper limit

V      17.5
B      19.1
U      18.8

The magnitudes are based on preliminary zero-points, measured in
orbit, and will require refinement with further calibration.

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