GCN Circular 45906

Subject

GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde

Event

GRB 261011A

Date

2026-10-11T18:53:04Z (7 days ago)

Edited On

2026-10-16T12:34:21Z (2 days ago)

From

Y.C. Kang at Peking University <yckang@stu.pku.edu.cn>

Edited By

Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Y.C. Kang at Peking University <yckang@stu.pku.edu.cn>

Via

Web form

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:

We 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 ), using a 28cm optical telescope located in Chengde, Hebei, China. The observation began on 2026-10-11 at 15:46:33 UT, approximately 1.99 hr after the Swift/BAT trigger.

We 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 ; Fu et al., GCN ; Izzo et al., GCN ; Wu et al., GCN ; Yin et al., GCN ; Shi et al., GCN ; Aryan et al., GCN ; Buckley et al., GCN ). We derive a 5-sigma upper limit of L > 19.65 mag.

Preliminary 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.

The 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.