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GCN Circular 30543

Subject
GRB 210726A: Deep CAHA 2.2m limit
Date
2021-07-29T00:01:25Z (3 years ago)
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), A. Gardini, and I. Hermelo (both CAHA) 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 CAFOS mounted at the 2.2m Calar Alto telescope (Almeria, Spain), 
under good conditions but at high airmass, starting July 26, 20:52:13 
UT, 1.553 h after the GRB. We obtained 15 x 180 s images in r'.

Within the XRT error circle, we do not detect any source down to r' > 
24.2 mag (AB magnitude) at 0.081518 d (1.956 h) after the burst, in 
agreement with but deeper than limits presented by Hu et al., GCN 
#30525; Watson et al., GCN #30534.

Watson et al. suggest an object about 3" away as a possible host-galaxy 
candidate. We clearly detect this object and measure r' = 22.26 +/- 0.06 
mag. This value is in agreement with detections from the PanSTARRS and 
SDSS surveys, and therefore there is no evidence of excess emission that 
could be an afterglow superposed on the host galaxy.
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