GCN Circular 31229
Subject
GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
Event
Date
2021-12-14T16:25:45Z (4 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (Obs. Cote d���Azur), D.A. Kann, C. Thoene,
J.F. Agui Fernandez, M. Blazek (HETH/IAA-CSIC), I. Vico and
A. Guijarro (CAHA) report:
We obtained further i-band imaging of the afterglow of GRB 211211A
(Fermi team GCN31201; D���Ai et al. GCN31202; Zheng and Filipenko
GCN 31203) from CAFOS/2.2m CAHA 2.66 days after the burst onset.
The observation consisted of 20x120s exposures under good seeing
and yielded a faint detection. The light curve decay, compared to our
previous observation from Calar Alto (de Ugarte Postigo et al., GCN
31228) indicates an extreme decay index of alpha = 3.25+/-0.40.
This is similar to what is observed from the XRT light curve, which
currently decays with an index of 3.2 (-0.7,+0.8)
(https://www.swift.ac.uk/xrt_live_cat/01088940/ <https://www.swift.ac.uk/xrt_live_cat/01088940/>; Evans et al. 2007;
Evans et al. 2009). We note that this is amongst the fastest post-break
decays that are normally observed for GRB afterglows.
Further observations with larger telescopes are encouraged.