{
  "eventId": "GRB 240821A",
  "format": "text/plain",
  "subject": "GRB 240821A: Colibri Optical Upper Limit",
  "bibcode": "2024GCN.37251....1B",
  "circularId": 37251,
  "submittedHow": "email-legacy",
  "version": 2,
  "createdOn": 1724446037638,
  "editedOn": 1724470829603,
  "editedBy": "Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov> on behalf of Alan Watson at UNAM <alan@astro.unam.mx>",
  "submitter": "Alan Watson at UNAM <alan@astro.unam.mx>",
  "body": "Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), S. Antier (OCA), Alan\nM. Watson (UNAM), and D. Akl (AUS)\n\nreport on behalf of:\n\nColibri Science Team: Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU),\nDamien Dornic (CPPM), J.-G. Ducoin (CPPM), Francis Fortin (IRAP), Simona\nLombardo (LAM), Francesco Magnani (CPPM), and Margarita Pereyra (UNAM),\n\nColibri Engineering Team: François Dolon (UAR Pytheas), François Agneray\n(LAM), Fernando Angeles (UNAM), Thomas Auphan (CPPM), Hafid Benamar (CPPM),\nJérémie Boy (IRAP), Edgar Cadena Zepeda (UNAM), Salvador Cuevas (UNAM),\nAlejandro Farah (UNAM), Liliana Figueroa Carrilo (UNAM), Johan Floriot\n(LAM), Jorge Fuentes-Fernandez (UNAM), Pascal Gallais (CEA), Rosalía \nLangarica (UNAM), Arthur Langlois (IRAP), Julien Lecubin (UAR Pytheas), \nEduardo López Ángeles (UNAM), Erica E. Lugo-Ibarra (UNAM), Adrien Malgoyre \n(UAR Pytheas), Chrystel Moreau (LAM), José Luis Ochoa Abundis (UNAM), \nMaría H. Pedrayes-López (UNAM), Samuel Ronayette (CEA), Aurelia Secroun \n(CPPM), Jaime Ruiz Díaz-Soto (UNAM), Silvio Tinoco (UNAM), and \nHervé Valentin (IRAP)\n\nSVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang\n(IHEP), Stéphane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA),\nZi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea\nGoldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC),\nEn-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing\nWang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)\n\nWe imaged the field of GRB 240821A detected by SVOM/ECLAIRs/GRM, Fermi-GBM,\nEIRSAT-1 GMOD (GCN circ. 37219, 37220, 37226, 37227, 37232, 37239)) during\nthe commissioning of the Colibri (SVOM/F-GFT) telescope at the Observatorio\nAstronómico Nacional on the Sierra de San Pedro Mártir in Mexico.\n\nThe observations started 11.1 hours after the GRB trigger and finished 3.5\nhour later. We obtained 7530 seconds of exposure with the engineering test\ncamera in a red filter that approximates SDSS r. The proximity of the\nsource to the moon made the limits relatively shallow.\n\nThe data have been reduced by a single data processing pipeline STDPIPE\n(Karpov et al., 2022) and calibrated against the PS1 catalog.\n\nWe do not find any optical counterpart in a field of 13 arcmin to a side\ncentered on RA, Dec = 354.23, -10.18 (J2000).\n\nWe estimate an upper limit of 20 mag in r-band (5 sigma).\n\nNote that EP-FXT sources and Swift-XRT sources are in the field of view of\nColibri (GCN 37230, GCN 37249)\n\nThis report is consistent other optical observations by GRANDMA (GCN\n37225), GMG (GCN 37242), SVOM/VT (GCN 37243), Jinshan (GCN 37245), LCO (GCN\n37246), REM (GCN 37247).\n\nWe warmly thank the COLIBRI engineering team, D. Turpin, A. Klotz, S.\nKarpov, E. Jiménez Bailon, and the staff of the Observatorio Astronómico\nNacional on the Sierra de San Pedro Mártir.\n"
}