TITLE:   GCN CIRCULAR
NUMBER:  43986
SUBJECT: GRB 260310A/AT 2026fgk: Bok spectroscopic observation
DATE:    26/03/13 11:30:56 GMT
FROM:    Brian Hsu at University of Arizona <bhsu@arizona.edu>

B. Hsu (U of Arizona), M. Shrestha (Monash U), Jennifer Andrews (Gemini-N/NOIRLab), D. J. Sand (U of Arizona), N. Franz (U of Arizona), J. Pearson (U of Arizona), C. Christy (U of Arizona), C. L. Ransome (U of Arizona), Bhagya Subrayan (U of Arizona), K. Bostroem (U of Arizona), G. Hosseinzadeh (UCSD), N. Smith (U of Arizona)
 
We observed the possible optical counterpart to GRB 20260310A/AT2026fgk (Konno et al., GCN 43974; Lipunov et al., GCN 43978, discovered by GOTO; O'Neill et al. 2026, TNS Discovery Report 294132) on UT 2025-03-13T06:02:23.850 using the B&C spectrograph on the 90-inch Bok telescope. 

The optical counterpart is clearly visible. The optical spectrum shows a featureless red continuum, although we find a strong, narrow emission line at 7566 Angstroms that we attribute to H-alpha from the candidate host galaxy at z = 0.153, which is in agreement with the redshift obtained by Hinds et al., GCN 43977. Additional follow-up observations are encouraged.