TITLE: GCN CIRCULAR NUMBER: 42333 SUBJECT: GRB 251013C: Leavitt Observatory optical photometry DATE: 25/10/17 20:56:44 GMT FROM: leavittob@gmail.com
E. Pavoni, L. Moretti (Leavitt Observatory, Italy)
Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani
In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report:
We performed a follow-up observation of the field of GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) using our 250mm f/8 Ritchey-Chrétien telescope (Leavitt Observatory, Manciano, Italy).
Observations began on 2025-10-13 at 19:09:11 UT (≈ 1.5 hours after the trigger) and ended at 22:19:55 UT. A series of images in Rc and Ic filter (Johnson-Cousins system) was obtained under good weather conditions.
We clearly detected a bright afterglow positionally consistent with the source reported in previous circulars. The OT coordinates are:
RA (J2000) = 23:03:20.55 Dec(J2000) = -00:12:35.12 (±2 arcsec on both axes)
Photometry was performed using nearby stars from the Pan-STARRS catalog (magnitudes converted using Lupton (2005) equations) and analysed with AstroImageJ (2017AJ....153...77C). The following magnitudes were measured (not corrected for Galactic extinction):
HJD at mid-exposure Filter Mag. Mag. err. 2460962.30386029 Rc 15.38 0.01 2460962.30725948 Rc 15.51 0.01 2460962.30996796 Rc 15.67 0.01 2460962.31258558 Rc 15.73 0.02 2460962.31556121 Rc 15.74 0.02 2460962.31806558 Rc 15.76 0.02 2460962.32017580 Rc 15.86 0.02 2460962.32228375 Rc 15.84 0.02 2460962.32439216 Rc 15.84 0.02 2460962.32650057 Rc 15.89 0.02 2460962.32860895 Rc 15.90 0.02 2460962.33071795 Rc 15.92 0.02 2460962.33282552 Rc 15.97 0.02 2460962.33493454 Rc 15.96 0.02 2460962.33704239 Rc 16.04 0.02 2460962.33915074 Rc 16.12 0.02 2460962.34126105 Rc 16.12 0.02 2460962.34337272 Rc 16.19 0.02 2460962.34548188 Rc 16.27 0.02 2460962.34759218 Rc 16.29 0.02 2460962.35500912 Rc 16.33 0.02 2460962.35926398 Rc 16.34 0.02 2460962.36351931 Rc 16.37 0.02 2460962.36777694 Rc 16.41 0.02 2460962.37203488 Rc 16.56 0.03 2460962.37629036 Rc 16.46 0.03 2460962.38920934 Rc 16.64 0.03 2460962.39346447 Rc 16.54 0.03 2460962.39772065 Rc 16.69 0.03 2460962.40623373 Rc 16.80 0.04 2460962.41049247 Rc 16.75 0.03 2460962.41474858 Rc 16.93 0.04 2460962.41900117 Rc 16.82 0.04 2460962.42325452 Rc 16.72 0.04 2460962.42750818 Rc 17.11 0.05
2460962.35287059 Ic 15.94 0.03 2460962.35712512 Ic 15.95 0.03 2460962.36138024 Ic 15.92 0.03 2460962.36563799 Ic 15.86 0.03 2460962.36989563 Ic 16.05 0.04 2460962.37415044 Ic 16.25 0.04 2460962.38706915 Ic 16.14 0.04 2460962.39132719 Ic 16.19 0.04 2460962.39558282 Ic 16.33 0.05 2460962.39983877 Ic 16.23 0.05 2460962.40409469 Ic 16.37 0.05 2460962.40835283 Ic 16.40 0.05 2460962.41261135 Ic 16.43 0.06 2460962.41686396 Ic 16.24 0.05 2460962.42111700 Ic 16.42 0.06 2460962.42537095 Ic 16.49 0.06 2460962.42997457 Ic 16.68 0.07 2460962.43422909 Ic 16.63 0.07
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Reference: https://leavittobservatory.altervista.org
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