{
  "body": "S.-Y. Wu, M. Gritsevich, I. Perez-Garcia, E.  Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC,  Granada), C. Perez del Pulgar (Univ. of Malaga), Y.-D. Hu (GXU, Guanxi), B.-B. Zhang (Nanjing Univ.), and A. Maury (Space Obs., San Pedro de Atacama), on behalf of a larger  collaboration, report:\n\nFollowing the detection of GRB 260421B by Fermi (Fermi Team, GCN 44360, Preis and Greiner, GCN 44361) and SVOM (Zhao et al. GCN 44362), the BOOTES-7 telescope at  the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) automatically observed the GRB location starting on Aug. 21, 04:28:36 UT (i.e. 15 min after GRB onset).\n\nA series of images in clear filter were gathered and we identify the fading optical afterglow reported by He et al. (GCN 44363) Sánchez-Álvarez et al. (GCN 44364) and Turpin et al. (GCN 44365) at coordinates RA: 12:40:00.50 Dec: -17:44:24.0 (+/- 0.5 “). Preliminary magnitude is 18. Further data analysis is ongoing.\n\nWe would like to thank the staff at San Pedro de Atacama Space Observatory for their excellent support.\n\n",
  "circularId": 44366,
  "submittedHow": "email",
  "eventId": "GRB 260421B",
  "createdOn": 1776749873205,
  "submitter": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>",
  "subject": "GRB 260421B: BOOTES-7 early optical afterglow detection",
  "bibcode": "2026GCN.44366....1W"
}