GCN Circular 46090
Yacheng Kang (PKU), Xinmiao Zhao (PKU), and Fangzhou Ren (PKU) report on behalf of the PKU HiTF (High-energy Transients Follow-up) group:
We observed the field of GRB 261029A, triggered by Fermi/GBM (Fermi GBM team, GCN 46071; T0 = 2026-10-29T01:27:03) and SVOM/ECLAIRs (Goto et al., GCN 46072), using the PKU 60cm telescope at Xinglong Observatory, NAOC. Observations were conducted in the r and i bands at approximately 10 hr after the Fermi/GBM trigger.
In the stacked r- and i-band images, we clearly detect the optical counterpart in the difference images at a position consistent with previous GCN reports (O'Neill et al., GCN 46073; He et al., GCN 46078; Wang et al. GCN 46079; De et al., GCN 46080; Cotter et al., GCN 46081; Álvarez et al., GCN 46083; Yin et al., GCN 46084; Shi et al., GCN 46088). Preliminary photometry is calibrated against nearby Pan-STARRS field stars and reported in the AB magnitude system, without correction for Galactic extinction.
The observation log is summarized below following the time sequence:
| Date | Start_UT | T_mid - T0 (days) | Filter | Exposure (s) | Magnitude (AB) |
|---|---|---|---|---|---|
| 2026-10-29 | 10:57:38.04 | 0.42 | r | 6 * 600 | 19.74 +/- 0.07 |
| 2026-10-29 | 12:02:02.32 | 0.46 | i | 6 * 600 | 19.74 +/- 0.19 |
Further optical follow-up observations are encouraged.
The PKU 60cm Telescope is operated by the Department of Astronomy, Peking University. The PKU HiTF group is dedicated to rapid follow-up observations of high-energy transients.