{
  "bibcode": "2010GCN.10814....1X",
  "body": "D. Xu (Weizmann Inst.), P. Jakobsson (Univ. Iceland), A. Irrgang (Karl \nRemeis Observatory & ECAP) report on behalf of a larger collaboration:\n\nWe observed the field of GRB 100528A (Del Monte et al., GCN 10810; Grupe \net al., GCN 10813) with the NOT equipped with ALFOSC in the B, V, R, and \ni filters. Observations started on May 29 at 04:08 UT (26.34 hrs after \nthe GRB). We obtained 3x180 s frames in each filter.\n\nAn optical source is found at the UVOT position (Grupe et al., GCN \n10813) and is clearly detected in the stacked frame in each filter. \nPreliminary analysis shows the following Vega magnitudes:\n\nm(B)=21.71+/-0.06  (mid_time=26.4417 hr)\nm(V)=20.95+/-0.03  (mid_time=26.6751 hr)\nm(R)=20.48+/-0.02  (mid_time=26.9090 hr)\nm(i)= 20.02+-0.02   (mid_time= 27.1415 hr),\n\nwhich are mainly calibrated against the #1178-0655113 star in the USNO \nB1 catalog and the Galactic extinction is not taken into account.\n\nThe source is very likely the afterglow of GRB 100528A as there exists \ndecay in the V filter compared with the measurement in Grupe et al. (GCN \n10813).",
  "circularId": 10814,
  "createdOn": 1275150612000,
  "email": "dong@astro.ku.dk",
  "subject": "GRB 100528A: NOT optical observation",
  "submitter": "Dong Xu at DARK,NBI  <dong@astro.ku.dk>",
  "eventId": "GRB 100528A"
}