{
  "bibcode": "2009GCN..9221....1I",
  "body": "M. Im, Y. Jeon, C. Choi, W. Park, I. Lee Seoul National Univ),\n  Y.-B. Jeon (KASI) and Y. Urata (NCU) on behalf of EAFON team.\n\n  We took a series of Y-band photometry calibration data\n  for the field of GRB090423 using the 1.0m telescope at\n  Mt. Lemmon (Arizona, US) operated by the Korea Astronomy\n  Space Science Institute.\n\n   For the Y-band photometry standards, we used P239-C and\n  GD140 from UKIRT faint standards, and HIP 50459, a A0V star\n  from Hipparcos catalog. The zero points obtained for\n  these standards are applied to our observation of\n  the GRB090423 field, yielding Y-band photometry (Vega) for\n  objects in the GRB field down to Y(MKO) ~ 17.5 magnitude at 10-sigma.\n  The expected zero point accuracy is ~0.1mag.\n  To derive AB mag, add 0.63 mag to the values listed in\n  the catalog.\n\n  The calibration data and finding charts are available at\n  http://astro.snu.ac.kr/~mim/grb/readme\n  http://astro.snu.ac.kr/~mim/grb/grb090423_ycal.dat\n  http://astro.snu.ac.kr/~mim/grb/yobj.reg\n  http://astro.snu.ac.kr/~mim/grb/chart.gif\n\n  We thank the LOAO operator, J. Yoon for his assistance for this\n  observation.",
  "circularId": 9221,
  "createdOn": 1240576992000,
  "email": "mim@astro.snu.ac.kr",
  "subject": "GRB090423: Y-band field calibration",
  "submitter": "Myungshin Im at Seoul Nat U  <mim@astro.snu.ac.kr>",
  "eventId": "GRB 090423"
}