TITLE: GCN CIRCULAR NUMBER: 39846 SUBJECT: GRB 250322A: Gemini-South optical observations DATE: 25/03/23 03:06:38 GMT FROM: Charles Kilpatrick at Northwestern U ckilpatrick@northwestern.edu
C. D. Kilpatrick and W. Fong (Northwestern) report on behalf of a larger collaboration:
We observed the location of the short-duration GRB 250322A (Gupta et al., GCN 39835) with the Gemini Multi-Object Spectrograph (GMOS) mounted on Gemini-South under Program GS-2025A-Q-112 (PI: Fong). We obtained 10x120-sec imaging each in the r- and i-bands starting at 2025-03-23 00:06:31 UT (8.0 hrs post-burst), at a median airmass of 1.3 and seeing of 0.6-0.9’’.
Within or proximate to the enhanced XRT localization (Goad et al., GCN 39841), we do not detect any additional sources relative to Pan-STARRS1, to 3-sigma limits of r > 24.2 AB mag and i > 24.4 AB mag (calibrated to Pan-STARRS), consistent with the non-detections reported (Martin-Carrillo et al., GCN 39842; Becerra et al. GCN 39845).
Regarding the galaxy within the XRT position, first pointed out by Martin-Carrillo et al. (GCN 39842), we measure magnitudes of r = 21.7 +/- 0.1 AB mag and i = 21.1 +/- 0.1 AB mag. We note that these are ~0.3-0.6 mag brighter than the catalogued Pan-STARRS values (Flewelling et al., 2020, ApJS, 251, 7). We caution that these differences are not significant enough to claim presence of an afterglow and could instead be due to a combination of filter differences or aperture differences for the catalog values.
Further observations are planned to monitor the variability of the source. We thank Jennifer Andrews, Veronica Firpo, Daniel May, and Aleksandar Cipota for the rapid scheduling and execution of these observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/39846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...