GCN Circular 30551
Subject
GRB 210724A: Early CAHA 2.2m limit
Date
2021-07-30T12:37:10Z (4 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 in-flight XRT afterglow position (revised in Evans et
al., GCN #30547) of GRB 210724A (D'Avanzo et al., GCN #30497) with CAFOS
mounted at the 2.2m Calar Alto telescope (Almeria, Spain), under very
adverse conditions (high airmass, strong Calima, clouds, bad seeing,
strong moonlight - the works). We obtained 10 x 180 s images in r',
starting on July 24, 21:07:08 UT (0.8831 h after the burst).
At the position of the GTC afterglow candidate (de Ugarte Postigo et
al., GCN #30511), we detect no source down to r' > 22.0 mag (AB
magnitude) against PanSTARRS comparison stars, at midtime 0.0482 d
(1.1569 h) after the burst. This is of similar depth as the detection by
de Ugarte Postigo et al., GCN #30511, perhaps indicating a slowly rising
afterglow, or at least one that is not steeply decaying.