{
  "bibcode": "2021GCN.29291....1N",
  "body": "M. Nakamura, K. Hasuda, T. Sakamoto (AGU)\n\nWe observed the field of GRB 210104A (Troja et al., GCN Circ. 29233;\nMalacaria et al., GCN Circ. 29246; Frederiks et al., GCN Circ. 29258;\nCherry et al., GCN Circ. 29268) with the 14-inch AGU Robotic Optical\nMonitor for Astrophysical object - Narrow (AROMA-N) located at\nthe Sagamihara campus of Aoyama Gakuin University.\n\n60 images of 60 sec exposures were taken in the R filter starting\nfrom January 4 11:29:50 (UT) about 171 seconds after the trigger and\nstopped on January 4 12:45:20 (UT).  We detected the optical afterglow\nat the consistent position previously reported (Troja et al., GCN Circ. 29233;\nXin et al., GCN Circ. 29235; Hu et al., GCN Circ. 29236; Hosokawa et al.,\nGCN Circ. 29237; Kim et al., GCN Circ. 29238, 29265; Lipunov et al.,\nGCN Circ. 29239; Horiuchi et al., GCN Circ. 29241; Breeveld et al.,\nGCN Circ. 29247; Zhu et al., GCN Circ. 29252; Paek et al., GCN Circ. 29254;\nKumar et al., GCN Circ. 29257; Smartt et al., GCN Circ. 29262; Romanov,\nGCN Circ. 29269; Anandagoda et al., GCN Circ. 29273; Gokuldass, GCN Circ. 29274;\nMao et al., GCN Circ. 29275; Moskvitin et al., GCN Circ. 29277;\nBelkin et al., GCN Circ. 29286).  The clear decay signature was visible in our\nimages.  The magnitudes of the initial 60 s image and the combined\nimage from T+2915 sec to T+3577 sec images (total exposure of 540 sec)\nwere 14.3 mag and 17.1 mag.  The afterglow light curve of our data showed\nthe initial temporal decay of -1.4 following by the shallow decay of -0.6\nat the break around T+650 sec.  Our reported magnitudes are calibrated using\nthe USNO-B1 catalog.",
  "circularId": 29291,
  "createdOn": 1610433402000,
  "email": "tsakamoto@phys.aoyama.ac.jp",
  "subject": "GRB 210104A: AROMA-N Optical Afterglow Detection",
  "submitter": "Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>",
  "eventId": "GRB 210104A"
}