{
  "subject": "GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde",
  "body": "Chenxi Bao (PKU), Yacheng Kang (PKU), Xinmiao Zhao (PKU), and Zhuokai Liu (PKU) report on behalf of the Interestar Collaboration and the PKU HiTF (High-energy Transients Follow-up) group:\n\nWe observed the field of GRB 261011A, detected by Swift/BAT (Cenko et al., GCN 45896; T0 = 2026-10-11T13:46:41) and SVOM/ECLAIRs (Huang et al, GCN 45895), using a 28cm optical telescope located in Chengde, Hebei, China. The observation began on 2026-10-11 at 14:33:32 UT, approximately 0.78 hr after the Swift/BAT trigger. \n\nWe obtained the Luminance-band image with a total exposure time of 1800 s. No significant source is detected at the position of the reported optical counterpart (Cenko et al., GCN 45896; O'Neill et al., GCN 45897; Fu et al., GCN 45898; Izzo et al., GCN 45899; Wu et al., GCN 45900; Yin et al., GCN 45901; Shi et al., GCN 45903; Aryan et al., GCN 45904; Buckley et al., GCN 45905). We derive a 5-sigma upper limit of L > 19.65 mag. \n\nPreliminary photometric calibration was performed using nearby catalogued field stars. The reported limit is an approximate AB-equivalent magnitude and has not been corrected for Galactic extinction. Our non-detection is consistent with the reported fading behavior of the optical counterpart. Further optical follow-up observations are encouraged.\n\nThe 28cm optical telescope is operated by the Interestar Collaboration, which contributes to the rapid follow-up of high-energy transients as part of the PKU HiTF group.",
  "circularId": 45906,
  "submitter": "Y.C. Kang at Peking University <yckang@stu.pku.edu.cn>",
  "eventId": "GRB 261011A",
  "version": 2,
  "editedOn": 1791745951315,
  "format": "text/markdown",
  "createdOn": 1791744784519,
  "eventType": [
    "GRB"
  ],
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Y.C. Kang at Peking University <yckang@stu.pku.edu.cn>",
  "submittedHow": "web"
}