TITLE: GCN CIRCULAR NUMBER: 39863 SUBJECT: GRB 250322A: further NOT optical observations DATE: 25/03/24 16:33:39 GMT FROM: Benjamin Schneider at MIT bschn@mit.edu
B. Schneider (LAM), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. M. Kadela (NOT and NBI) report on behalf of a larger collaboration:
We secured a second 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 7x360 s in the r-band, with mean time 2025 Mar 23.88 UT (29.7 hr after the GRB). Unfortunately, the delivered seeing is worse than in our first epoch (Martin-Carrillo et al., GCN 39842), taken 4.65 hr after the GRB (1.5 vs 1.0").
The galaxy noted by Martin-Carrillo et al. (GCN 39842), Becerra et al. (GCN 39844, 39845), Kilpatrick & Fong (GCN 39846), and Fong et al. (GCN 39852) is detected in our second epoch. Image subtraction was carried out using Hotpants. No residuals are detected in the difference image, corresponding to a limiting magnitude of r > 23.2 (AB).
For the galaxy, we measure (in our first epoch) r = 22.04 +/- 0.12 (AB), calibrated against nearby Pan-STARRS point-like objects. Considering a 2.5”-radius XRT error circle (Goad et al., GCN 39841; Perri et al., 39855), we estimate a chance association probability of 2%, which provides moderate evidence for a physical association with the GRB.
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