GCN Circular 30211
Subject
GRB 210610A: CAHA 2.2m observations and light-curve behavior
Event
Date
2021-06-11T20:58:31Z (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), J. F. Agui Fernandez, C. C. Thoene, M. Blazek (all
HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and S. Pedraz (all CAHA)
report:
We observed the afterglow (Page et al., GCN #30160; Hosokawa et al.,
GCNs #30161, #30169; Xu et a., GCN #30162; Kumar et al., GCN #30163;
Lipunov et al., GCN #30166; de Wet et al., GCN #30168; Sun et al., GCN
#30185; Watson et al., GCN #30191; Zheng et al., GCN #30203) of GRB
210610A, discovered by Swift (Page et al., GCN #30160) and also detected
by Konus-Wind (Frederiks et al., GCN #30197) at redshift z=3.54 (Zhu et
al., GCN #30164; Dutta et al., GCN #30200). with CAFOS mounted on the
2.2m telescope at Calar Alto, Almeria, Spain. We obtained 5 x 180 s in
Sloan i' before switching to observations of GRB 210610B. After these,
we obtained 3 x 300 s each in Sloan r' and g'.
The afterglow is detected in individual frames. Stacking the images, we
measure, against nearby comparison stars from the SDSS catalog (AB mags,
not corrected for Galactic extinction):
i' = 20.18 +/- 0.04 mag at 0.23677 d;
r' = 20.87 +/- 0.05 mag at 0.36333 d;
g' = 21.92 +/- 0.08 mag at 0.37687 d.
Using our data as well as data given in the GCN Circulars cited above,
we find that after 0.03 d, the light curve can be described with a
broken power-law fit, with alpha_1 = 0.84, alpha_2 = 1.24, and t_break =
0.16 d. Earlier data is brighter than the back-extrapolation of the fit,
indicating a steeper decay must have taken place.