{
  "bibcode": "2021GCN.30211....1K",
  "body": "D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, \nDARK/NBI), J. F. Agui Fernandez, C. C. Thoene, M. Blazek (all \nHETH/IAA-CSIC), A. Fernandez, I. Hermelo, and S. Pedraz (all CAHA) \nreport:\n\nWe observed the afterglow (Page et al., GCN #30160; Hosokawa et al., \nGCNs #30161, #30169; Xu et a., GCN #30162; Kumar et al., GCN #30163; \nLipunov et al., GCN #30166; de Wet et al., GCN #30168; Sun et al., GCN \n#30185; Watson et al., GCN #30191; Zheng et al., GCN #30203) of GRB \n210610A, discovered by Swift (Page et al., GCN #30160) and also detected \nby Konus-Wind (Frederiks et al., GCN #30197) at redshift z=3.54 (Zhu et \nal., GCN #30164; Dutta et al., GCN #30200). with CAFOS mounted on the \n2.2m telescope at Calar Alto, Almeria, Spain. We obtained 5 x 180 s in \nSloan i' before switching to observations of GRB 210610B. After these, \nwe obtained 3 x 300 s each in Sloan r' and g'.\n\nThe afterglow is detected in individual frames. Stacking the images, we \nmeasure, against nearby comparison stars from the SDSS catalog (AB mags, \nnot corrected for Galactic extinction):\n\ni' = 20.18 +/- 0.04 mag at 0.23677 d;\nr' = 20.87 +/- 0.05 mag at 0.36333 d;\ng' = 21.92 +/- 0.08 mag at 0.37687 d.\n\nUsing our data as well as data given in the GCN Circulars cited above, \nwe find that after 0.03 d, the light curve can be described with a \nbroken power-law fit, with alpha_1 = 0.84, alpha_2 = 1.24, and t_break = \n0.16 d. Earlier data is brighter than the back-extrapolation of the fit, \nindicating a steeper decay must have taken place.",
  "circularId": 30211,
  "createdOn": 1623445111000,
  "email": "kann@iaa.es",
  "subject": "GRB 210610A: CAHA 2.2m observations and light-curve behavior",
  "submitter": "Alexander Kann at IAA-CSIC  <kann@iaa.es>",
  "eventId": "GRB 210610A"
}