GCN Circular 31228
Subject
GRB 211211A: Further observations from CAFOS/2.2m CAHA
Date
2021-12-13T17:22:44Z (3 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 a second imaging observation of the optical afterglow
of GRB 211211A (Fermi team GCN31201; D���Ai et al. GCN31202;
Zheng and Filipenko GCN 31203) with CAFOS, mounted on the
2.2m telescope, at the Calar Alto Observatory (Almer��a, Spain).
The observation started at 04:47 UT (39.6 hr after the GRB) and
consisted of 30x90s in i-band. The optical afterglow is still detected,
at a magnitude (AB) of i = 22.45+/-0.09, as compared to field stars
from the SDSS catalogue. With respect to our earlier CAFOS
photometry (de Ugarte Postigo et al. GCN 31218) this implies a
rapid decay rate of alpha = 1.65, where F_nu ~ t^-alpha, which
would indicate a post-jet break evolution.