{
  "bibcode": "2021GCN.29502....1K",
  "body": "D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, \nDARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all \nHETH/IAA-CSIC), P. Minguez, and S. Pedraz (both CAHA) report:\n\nWe again observed the afterglow (Laha et al., GCN #29444, Lipunov et \nal., GCN #29447, de Ugarte Postigo et al., GCN #29450, Breeveld & Laha, \nGCN #29457, Strausbaugh & Cucchiara, GCN #29459, Jelinek et al., GCN \n#29469, Kann et al., GCN #29476, Dimple et al., GCN #2948 of GRB 210210A \n(Laha et al., GCN #29444) with CAFOS mounted on the 2.2m Calar Alto \ntelescope (Almeria, Spain). We obtained 6 x 600 s image in Rc. We detect \nthe optical afterglow faintly in the stacked Rc image.\n\nUsing the same comparison star used by de Ugarte Postigo et al., and \ntransforming to Rc following the equations of Lupton (2005), then \ntransforming back to AB magnitudes, we derive a preliminary magnitude:\n\nRc = 23.05 +/- 0.14 mag at 3.129261 days after the trigger.\n\nUsing the R-band magnitudes from the GCNs listed above, now also \nincluding Dimple et al., GCN #29488, we confirm the steeper decay found \nby Kann et al., GCN #29476, finding, with a host-galaxy magnitude as a \nfree parameter:\n\nalpha_1 = 1.06 +/- 0.18,\nalpha_1 = 2.50 +/- 0.90,\nt_b = 0.45 +/- 0.23 days,\nm_h = 23.19 +/- 0.27 mag (AB).\n\nThis fit can be improved with a dedicated host-galaxy observation. We \nnote that the X-ray light curve also shows evidence for a possible jet \nbreak at 0.35 +0.27 -0.13 days, in agreement with our result.",
  "circularId": 29502,
  "createdOn": 1613215305000,
  "email": "kann@iaa.es",
  "subject": "GRB 210210A: CAHA 2nd epoch and jet break confirmation",
  "submitter": "Alexander Kann at IAA-CSIC  <kann@iaa.es>",
  "eventId": "GRB 210210A"
}