GCN Circular 33535

A. Catapano (OASDG), and L. Izzo (DARK/NBI) report:

We observed the field of GRB 230328B (Gropp et al., GCN #33527
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) with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy ( https://osservatorio.astrocampania.it/ ). We obtained two sets of 8x240s images each in the Rc and in the Ic filter under good weather conditions, with the two sets of observations separated by three hours each.

In the first dataset, we detect a faint source in the stacked Ic images at the enhanced position reported by Swift-XRT (Osborne et al., GCN #33529
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) and by optical telescopes (Pankov et al., GCN #33528
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; Belkin et al., GCN #33530
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, Lu et al., GCN #33534
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). We measure a preliminary magnitude of ~19.5 mag (AB), at exposure mid-time of MJD 60031.8 (5.1 hours after the GRB detection). We also report an upper limit of ~20.0 mag in the Rc band. In the second set of observations, the source is not detected in both filters, with upper limits of Rc > 20.2, and Ic > 19.8, respectively (MJD 60031.9, 8.1 hours after the GRB). The calibration was performed using nearby stars in the Pan-STARRS PS1 catalog, and using transformation equations to Rc and Ic magnitudes. Further analyses are ongoing.