TITLE: GCN CIRCULAR NUMBER: 39868 SUBJECT: GRB 250322A: third epoch of NOT optical observations DATE: 25/03/25 17:11:56 GMT FROM: Benjamin Schneider at MIT bschn@mit.edu
D. B. Malesani (DAWN/NBI and Radboud), B. Schneider (LAM), A. Martin-Carrillo (UCD), A. M. Kadela (NOT and NBI) report on behalf of a larger collaboration:
We secured a third observation of the field of GRB 250322A (Gupta et al., GCN 39835; Tembhurnikar et al., GCN 39849) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. Our observation consisted of 5x600 s in the r-band, with mean time 2025 Mar 24.86 UT (2.19 days after the GRB). This observation reaches a depth comparable to our first epoch (Martin-Carrillo et al., GCN 39842), taken at 4.65 hr after the GRB, unlike our second epoch (Schneider et al., GCN 39863), which suffered from worse seeing.
Image subtraction of our third epoch from the first was carried out using HOTPANTS. No residuals are detected in the difference image, down to a limiting magnitude r > 23.8 AB (calibrated against Pan-STARRS). This limit is consistent with, but strengthens, our earlier determination r > 23.2 (Schneider et al., GCN 39863).
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