{
  "bibcode": "2020GCN.27971....1F",
  "body": "S.Y. Fu, Z.P. Zhu, X. Liu, D. Xu, J. Zheng, A.Y. Zhou (NAOC) report:\n\nWe continued to observe the field of GRB 200613A (Fermi GBM team, GCN \n27926; Bissaldi et al., GCN 27930; Ohno et al., GCN 27931) using the \nXinglong-2.16m telescope equipped with the BFOSC camera. Observations \nwere carried out starting at 12:55:02 UT on 2020-06-16, and 5x300s \nR-band frames were obtained.\n\nThe optical afterglow (e.g., Kann et al., GCN 27935; Kennea et al., GCN \n27936; Pozanenko et al., GCN 27937; Izzo et al., GCN 27939; Zhu et al., \nGCN 27943; Marshall, GCN 27944; Liu et al., GCN 27949; Belkin et al., \nGCN 27958) is still well detected in our stacked image, with R = 21.07 \n+/- 0.21 mag (at Tmid-T0 = 3.3175 days post-burst), calibrated with \nnearby Pan-STARRS1.\n\nCompared with our previous measurements, the afterglow now has turned to \ndecay quickly, with a temporal decay index of  \\alpha ~ 2.5 and a break \ntime of ~ 2.3 days post-burst. This break can be interpreted as a jet break.\n\nFurther observations are planned.",
  "circularId": 27971,
  "createdOn": 1592357974000,
  "email": "dxu@nao.cas.cn",
  "subject": "GRB 200613A: Jet-break from Xinglong-2.16m optical observations",
  "submitter": "Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>",
  "eventId": "GRB 200613A"
}