{
  "bibcode": "2021GCN.30338....1K",
  "body": "D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, \nDARK/NBI), M. Jelinek (ASU CAS Ondrejov), M. Blazek, C. Thoene, J. F. \nAgui Fernandez (all HETH/IAA-CSIC), and P. Minguez (CAHA) report:\n\nWe re-observed the afterglow of GRB 210619B (D'Avanzo et al., GCN \n#30261) with CAFOS mounted at the 2.2m Calar Alto telescope (Almeria, \nSpain). Image depth was influenced by moonlight but conditions were \ngood. We obtained 20 x 180 s images in r'.\n\nThe afterglow is faintly detected in the stacked image. Against \nPan-STARRS comparison stars, we derive r' = 22.56 +/- 0.16 mag at \n6.12346 d after the trigger.\n\nUsing selected data from GCN Circulars (Jelinek et al., GCN #30263, \n#30281; Pellegrin et al., GCN #30268; Perley, GCN #30271; Zheng & \nFilippenko, GCN #30273; Blazek et al., GCN #30274; Kann et al., GCN \n#30275; Xin et al., GCN #30277; D'Avanzo et al., GCN #30288; Moskvitin & \nMaslennikova, GCNs #303291, #30303, #30309; Romanov, GCN #30292; Hu et \nal., GCN #30293; Zhu et al., GCN #30294; Belkin et al., GCN #30299; \nRomanov & Lane, GCN #30305; Vinko et al., GCN #30320), we find the \nafterglow after 0.057 d can be fit by a smoothly broken power-law with a \nsharp break and parameters alpha_1 = 0.742 +/- 0.013, alpha_2 = 1.221 \n+/- 0.045, and break time t_b = 0.465 +/- 0.048 d (40136 +/- 4108 s).\n\nThis fully confirms the steepening decay reported by Jelinek et al., GCN \n#30281; Kumar et al., GCN #30286.\n\nNote that the best fit of the X-ray light curve at the time finds \nalpha_1 = 0.978 +0.012 -0.019, alpha_2 = 1.50 +/- 0.035, t_b = 0.152 \n+0.015 -0.024 d (13100 +1300 -2100 s). However, the early decay (alpha_0 \n= 0.773 +0.087 -0.141, up to 500 s) is very similar to the optical decay \nwe find from ~5000 s onward to the (optical) break. We note that the \npost-break decay slope would be extremely shallow if this were actually \na jet break, but no deviation from this decay is seen until ~6 d.",
  "circularId": 30338,
  "createdOn": 1624876167000,
  "email": "kann@iaa.es",
  "subject": "GRB 210619B: Deep CAHA 2.2m detection and late-time light curve behavior",
  "submitter": "Alexander Kann at IAA-CSIC  <kann@iaa.es>",
  "eventId": "GRB 210619B"
}