TITLE: GCN CIRCULAR NUMBER: 40588 SUBJECT: GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle DATE: 25/05/31 09:10:56 GMT FROM: Paolo D'Avanzo at INAF - OAB paolo.davanzo@inaf.it

P. D'Avanzo, (INAF-OAB), A. Melandri (INAF-OAR), L. Izzo (INAF - OACn), M. G. Bernardini (INAF-OAB & LUPM), R. Brivio, M. Ferro (INAF-OAB), M. Pedani (INAF-TNG) on behalf of the CIBO collaboration report:

We observed the field of the GRB 250530A detected by SVOM (Wang et al., GCN Circ. 40576) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filters starting on 2025-05-30T20:57:35 UT (i.e. 14.4 hours post T0). Within the refined Swift/XRT error circle (Evans et al., GCN Circ. 40579; see also: https://www.swift.ac.uk/SVOM/SVOM_FIELD00017/Source1.php) a faint object is detected in the co-added image at the following coordinates:

RA (J2000) = 12:26:50.53 Dec (J2000) = -02:34:32.0 +/- 0.3"

We note that these coordinates are consistent (within 0.4") with those of a catalogue source reported in the DESI Legacy Imaging Survey (Duncan et al., 2022, MNRAS, 512, 366).

From preliminary photometry, we estimate for this source J ~ 21.0 mag (Vega; calibrated against the 2MASS catalogue).

This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI : 10.26093/cds/vizier). The original description of the VizieR service was published in 2000, A&AS 143, 23.

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