TITLE: GCN CIRCULAR NUMBER: 41794 SUBJECT: GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery DATE: 25/09/11 12:51:17 GMT FROM: Benjamin Schneider at MIT <bschn@mit.edu> B. Schneider (LAM), A. Martin-Carrillo (UCD), M. Garnichey (LUX-Paris Obs.), V. D'Elia (ASI-SSDC), A. J. Levan (Radboud U.), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF-IAPS), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed again the field of GRB 250910A / EP250910a (Ma et al., GCN 41769; Götz et al. GCN 41770; Wu et al., GCN 41772; Li et al., GCN 41774; Liu et al., GCN 41776) using the ESO VLT UT4 (Yepun) equipped with the HAWK-I NIR camera. We obtained 15 min imaging in the J band, beginning on 2025-09-11 at 09:36:48 UT (1.26 days post-trigger). Carrying out image subtraction with HOTPANTS between our new and previous (Garnichey et al., GCN 41777) images, a clear transient source is detected at coordinates (0.5" error): RA(J2000) = 02:39:12.56 Dec(J2000) = -39:41:40.9 These coordinates are consistent with the EP/FXT X-ray location (Liu et al., GCN 41776) and Swift/XRT X-ray detection (https://www.swift.ac.uk/SVOM/SVOM_FIELD00036/). We measure for the transient a magnitude J = 22.73 +/- 0.08 (AB, at 5.2 hr post trigger), calibrated against nearby 2MASS stars and not corrected for Galactic extinction. We caution that strictly this is a lower limit to the source brightness, as it is possible that residual transient light was present in our second observation. The spatial association with the X-ray afterglow and its fading behavior indicate that this object is the NIR afterglow of GRB 250910A / EP250910a. We note that at this location, an extended optical source can be seen in the Legacy Survey (magnitudes g = 24.56, r = 23.80, i = 23.38, z = 23.66), likely being the host galaxy of this source. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Juan Carlos Olivares and Robert De Rosa. View this GCN Circular online at https://gcn.nasa.gov/circulars/41794. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...