{
  "subject": "EP250821a: iTelescope T-59 possible detection of the optical counterpart",
  "circularId": 42089,
  "body": "H. Ban, T. Katou, Y. Nagata, K. Hotta, Y. Kawakubo, M. Serino, T. Sakamoto (AGU)\n\nWe observed the field of EP250821a detected by the Einstein Probe (EP) \n(Hu et al., GCN Circ. 41459) with the iTelescope.Net\n(http://www.itelescope.net) T59 (Planewave 20\" CDK) telescope located at \nthe Siding Spring Observatory, Australia. We took nine images of 120-second \nexposures in the Red filter starting from August 21 at 10:25:34 (UT), \nabout 3 hours after the trigger, and stopped at 12:48:14 (UT). Please note \nthat there were no observations between 10:33 and 11:30, and \nbetween 11:39 and 12:41 due to our scheduling error.\n\nWe have a weak detection of the optical counterpart \n(Dichiara et al., GCN Circ. 41469; Li et al., GCN Circ. 41470; \nYao et al., GCN Circ. 41485) in the stacked image of the first \nthree exposures from 10:25:34 to 10:32:47 UT. The estimated magnitude \nis ~18.5. No optical counterpart was detected in the following six images \ncollected between 11:30:00 and 12:48:14 (UT). The 5-sigma upper limit \nof the stacked image of the last six images is 17.5 mag.",
  "format": "text/plain",
  "submitter": "Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>",
  "eventId": "EP250821a",
  "createdOn": 1759496377589,
  "bibcode": "2025GCN.42089....1B",
  "submittedHow": "web"
}