TITLE:   GCN CIRCULAR
NUMBER:  30545
SUBJECT: GRB 210726A: OSIRIS/GTC observations
DATE:    21/07/29 12:54:52 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. 
Tanvir (U. Leicester), and G. Gomez Velarde (GRANTECAN) report:

We observed the XRT afterglow position (Osborne et al., GCN #30524) of 
GRB 210726A (Bernardini et al., GCN #30523), classified as a short GRB 
(Tohuvavohu, GCN #30535; Palmer et al., GCN #30536; Veres, GCN #30540) 
with OSIRIS mounted on the 10.4m Gran Telescopio Canarias (Observatorio 
Astrofíisco Roque de Los Muchachos, La Palma, Canary Islands, Spain), 
under mediocre conditions and at high airmass, starting July 26, 
21:21:31 UT, 2.041 h after the GRB. We obtained a sequence of 30, 30, 
60, 30 s images in r' for a total integration time of 150 s.

Within the XRT error circle, we do not detect any source down to r' > 
24.4 mag (AB magnitude), measured against a nearby PanSTARRS fiel star, 
at 0.088533 d (2.125 h) after the burst, in agreement with Kann et al., 
GCN #30543.

The possible host galaxy (Watson et al., GCN #30534, Kann et al., GCN 
#30543) is found at r' = 22.04 +/- 0.05 mag, again in agreement with 
detections from the PanSTARRS and SDSS surveys.