TITLE: GCN CIRCULAR NUMBER: 39109 SUBJECT: GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations DATE: 25/02/01 00:21:27 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy giovannicalapai@tiscali.it

Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani.

Report:

We observed the field of GRB 250129A (Swift trigger=1285812, Page et al., GCN 39066) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3.

The observations were started at 2025-01-31 01:00 UT (approximately 44.25 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions.

The OT was detected at the following position:

RA (J2000.0) 13h 14m 42.38s Decl. (J2000.0) +05° 01' 50.8"

Photometry was obtained using nearby PanSTARRS stars as follows:

Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-01-31 02:34:24 UT 45.82 105x60s CR 20.14 +/-0.30

Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.

Our observations are consistent with other already reported Lipunov et al. (GCN 39070), Gompertz et al. (GCN 39072), Malesani et al. (GCN 39073), Izzo et al. (GCN 39074), Lipunov et al. (GCN 39075), Ghosh et al. (GCN 39077), Schneider et al. (GCN 39078), Brivio et al. (GCN 39079), Siegel et al. (GCN 39085), Zheng et al. (GCN 39090), Schlekat et al. (GCN 39091), Antier et al. (GCN 39096), Odeh et al. (GCN 39097), Ferro et al. (GCN 39098), Bochenek et al. (GCN 39099), Malesani et al. (GCN 39100), Romanov (GCN 39101), Zheng et al. (GCN 39102), Watson et al. (GCN 39104), Vinko et al. (GCN 39105), Akl et al. (GCN 39106), Moskvitin et al. (GCN 39107).

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