TITLE: GCN CIRCULAR NUMBER: 44571 SUBJECT: GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation DATE: 26/05/12 07:55:07 GMT FROM: Liping Xin at NAOC, SVOM <xlp@nao.cas.cn> J. Wang, L. P. Xin, J. Zheng, H. L. Li, C. Wu, Y. L. Qiu, X. H. Han, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, J. Y. Wei (NAOC) reports on behalf of SVOM follow-up team The follow-up for the optical counterpart (Wu et al. GCN 44547; Sasada et al. GCN 44549; Jiang et al. GCN 44551; Wu et al. GCN 44552; Waratkar et al. GCN 44556; Li et al. GCN 44557; Vijaykumar et al. GCN 44561) of GRB 260511B (Fermi GBM team GCN 44542; Godet et al. GCN 44543; Roberts et al. GCN 44544; Arya et al. GCN 44560; de Ugarte Postigo et al., GCN 44565; Lee et al, GCN 44567; Li et al., GCN 44568) within the errorbox of X-ray counterpart (Godet et al. GCN 44543; Li et al., GCN 44566;) was performed at 2026-05-11T12:46:21 UTC, about 1.76 hours after the trigger, using the NAOC 2.16m telescope at Xinglong observatory, China. A total of 2*1800s exposure was performed by BEFOSC spectrograph in our spectroscopic observation. The wavelength ranges from 4000-8800A in the obsever frame. After combining the two frames, absorption features of multiple ions: CIV, FeII and MgII can be identified at a common redshift of ~2.006. In addition, there is a feature possibly due to MgII double let resulted from an intervening system at redshift of 1.435. Our results are consistent with the report of redshift (de Ugarte Postigo et al., GCN 44565). The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495). View this GCN Circular online at https://gcn.nasa.gov/circulars/44571. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...