TITLE: GCN CIRCULAR NUMBER: 43009 SUBJECT: GRB 251205A: NOT optical observations DATE: 25/12/06 09:45:00 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute daniele.malesani@nbi.ku.dk
D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. K. Aris-Kiss (Helsinki), M. Korp-Lagg (Aalto University), S. Wedemeyer (Oslo), S. Armas Perez (NOT) report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 251205A (Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008) using the Nordic Optical Telescope (NOT) equipped with the StanCam camera. Observations started on 2025-12-06 at 05:25:33 UT (5.75 hr after the trigger). Five 150 s observations were taken using the StanCam “interference i” filter.
The optical afterglow is well detected in single images. At a mean time of 5.90 hr after the trigger, we measure a magnitude
i = 17.93 +- 0.03.
This magnitude is in the AB system and is not corrected for Galactic extinction. We note that, due to the small field-of-view of StanCam, only one star from the Pan-STARRS catalog could be used for photometric calibration. Considering that the StanCam i filter is (slightly) different from the Pan-STARRS one, an extra systematic error of 0.1 mag should be conservatively added to the photometric error budget.
View this GCN Circular online at https://gcn.nasa.gov/circulars/43009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...