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GCN Circular 36221

GRB240421B: Zadko Observations
2024-04-22T02:30:22Z (3 months ago)
Bruce Gendre at UWA <>
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B. Gendre, E. Moore, F. Panther, D. Coward, J. A. Moore (OzGrav-UWA),
and A. Klotz (IRAP-CNRS-OMP),

We imaged the field of GRB 240421B detected by SWIFT
(trigger 1223470) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 7.97h after the GRB trigger.
The elevation of the field increased from
25 degrees above horizon and weather conditions
were good.

The date of trigger : t0 = 2024-04-21T09:42:54.050

The first image is 60.0s exposure in tracking mode:
t0+28754.8s to t0+28814.8s : R > 16.2

We co-added a series of exposures:
t0+28754.8s to t0+29599.3s : R > 17.7

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon= 26.7039 lat=-21.4736
and the galactic extinction in R band is 0.7 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

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