{
  "createdOn": 1732278098410,
  "subject": "GRB241120A: OHP/T193 optical observations",
  "submitter": "Christophe Adami at LAM <christophe.adami@lam.fr>",
  "format": "text/plain",
  "circularId": 38296,
  "submittedHow": "web",
  "body": "C. Adami (LAM/Pytheas/AMU), M. Dennefeld (IAP), S. Basa (LAM/OHP/Pytheas/AMU) report on behalf of a \nlarger collaboration:\n\nWe observed the field of GRB241120A (Gotz et al., GCN 38280; Fermi GRM team, GCN 38279; Hamburg \net al., GCN 38285; Pankov et al., GCN 38291; Cherry et al., GCN 38295) using the T193cm telescope \nat Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. Four exposures \nwere obtained in the r-band (300s + 3x420s) from 2024 21 November 04:39 UT to 2024 21 November \n05:05 UT (~+23h after detection) with two positions on the sky (position \"1\" for exposures 1 and \n4, and position \"2\" for exposures 2 and 3) separated by a dithering of ~10arcsec. The moon was at an \nillumination of ~68% and at a distance of 56deg from target.\n\nThe combined frame has a detection upper limit of r~22.5+/-0.6 (5sigma limit). The photometric \ncalibration was performed using objects from the PanSTARRS catalog. The magnitudes are not \ncorrected for Galactic extinction.\n\nThere is no clear additional objects in the MISTRAL image as compared with the PanStarrs r-band \nimage except a source at 12:57:06.0 +52:08:26.6 (r~22.2+/-0.2). This source (apparently extended) \nis however only present in two of the four exposures we performed (position \"2\" exposures) and is \npossibly an internal reflection within the instrument due to the intense Moon illumination. More \nobservations are requested to check this point.\n\nWe also checked the candidate of Pankov et al. We clearly detect this object and measured a \nmagnitude of r~20.40+/-0.08 23h after the original detection. This object is also present in the \nPanStarrs r-band catalog at r~20.39+/-0.02. If this was the transient, it was back to its initial \nmagnitude 0.96 days after detection. This would be in good agreement with the light curve proposed by \nPankov et al.\n\nWe acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean Pierre \nTroncin and the SOPHIE observer Aleyna Adamson. \n",
  "bibcode": "2024GCN.38296....1A",
  "eventId": "GRB 241120A"
}