{
  "bibcode": "2025GCN.42269....1R",
  "submitter": "Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde@gmail.com>",
  "createdOn": 1760475080499,
  "body": "Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with:\nM.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report:\n\nFollowing the circular GCN 42222, in which N. A. Rakotondrainibe, C. Adami (LAM), D. Turpin, D. Götz (CEA/Irfu), H. Yang (IRAP), in which at 2025-10-13T17:39:42 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251013C (SVOM burst-id sb25101311) also detected by Fermi/GBM, I pointed at the coordinates RA(J2000)=23h 03m 22s: Dec(J2000)=-00d 12' 37\" and started my observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy.\nMember of:\nAAVSO - American Association of Variable Star Observers.\nGRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani.\n\nThe observations started at 20:04:39 UT of 2025/10/13, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope  SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME, using the V and Rc photometric filters.\nI took 20 unfiltered images of 60 sec in each filter. The images were added in groups of five to obtain a higher S/N\n   Start                  End               \n20:04:39 UT            20:56:46 UT         \n\nAll images, calibrated with masterdark and masterflat have been measured with Maxim DL software\nI have detected  a bright source at the enhanced position reported by GCNs (Konno et al. (GCN circ. 42226), Perez-Garcia et al. (GCN circ. 42225), Martin-Carrillo et al. (GCN circ. 42227), Masi (GCN circ. 42228), Palmerio et al. (GCN circ. 42229), Moskvitin et al. (GCN circ. 42230), Gompertz et al. (GCN circ. 42231), Watson et al. (GCN circ. 42241), López-Cámara et al. (GCN circ. 42242), Zhang et al. (GCN circ. 42248), Brosio et al. (GCN circ. 42251), Quintana-Ansaldo et al. (GCN circ. 42254), and Maksut et al. (GCN circ. 42256), U. Quadri et al.(GCN 42262), C. Adami et al.(GCN 42266), I. Peretto et al.(GCN 42267)  at following position\n\nRA (J2000.0)   23 03 20.55\nDec (J2000.0) -00 12 37.0\n\nwith the following photometry:\n\n\n  (JD)\t \t   Mag     Err       Filter\t\n2460962.3649074\t 17.259\t  0.101\t      V\n2460962.3561574\t 16.903\t  0.065\t      V\n2460962.3473842\t 16.697\t  0.041\t      V\n2460962.3374884\t 16.576\t  0.044\t      V\n2460962.3639930\t 16.5\t  0.044       Rc\n2460962.3552430\t 16.43\t  0.039       Rc\n2460962.3464815\t 16.281   0.027       Rc\n2460962.3365625\t 16.114   0.023       Rc\n\n\n\n\nMagnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations.\n\nNot corrected for galactic dust extinction..\n\n\n\nThe message may be cited.\n",
  "format": "text/plain",
  "eventId": "GRB 251013C",
  "subject": "GRB 251013C: Osservatorio Astronomico \"Nastro Verde\" optical observations: detection of an bright optical counterpart",
  "circularId": 42269,
  "submittedHow": "web"
}