{
  "circularId": 16,
  "eventId": "GRB 971214",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Tyler Barna at University of Minnesota <tylerpbarna@gmail.com>",
  "body": "GRB971214 Optical Observations and Calibrations                     #016\n\nA.A. Henden, C.B. Luginbuhl and F.J. Vrba, U.S. Naval Observatory\nFlagstaff Station, report a single measure of the OT reported by Halpern\net al. (IAUC 6788), obtained from a composite R-Band image with 80min\ntotal exposure spread over Dec 15.4535-15.5593 UT (midpoint Dec 15.5064) as\nR=21.67 +/- 0.10.  This is in effect a differential magnitude with\nrespect to stars 1,5-9 listed in the table below.  We caution that this\nmeasure is approximate since we as yet have no calibrated color\ninformation for the OT to permit accurate transformation to the\nstandard system; the error of +/- 0.10 mag includes only the photon\nstatistical contribution and does not include any error introduced by\nthe lack of the color correction.  We would like to here acknowledge\nthe assistance of Jan van Paradijs at UAH/University of Amsterdam and\nJ. Heise at SRON Utrecht, whose prompt dissemination of the SAX-WFC\nposition allowed us to make this early observation.\n\nLocal Standards in the GRB971214 Field\n\nWe have further obtained calibrated BVR photometry for several objects\nnear the OT position, and offer them as local \"standards\" for\ncalibrating measures of the OT.  The \"standards\" are listed here with\nRA and DEC positions based on the GSC; we omit the RA hours (all 11)\nand Declination degrees (all +65).\n\n Obj     RA (2000) DEC      B     err     V     err     R     err    I     err\n  1   56 29.896 12 16.29  17.651 0.024  16.835 0.011  16.370 0.009\n  2   56 25.832 11 36.29                              20.1   0.1\n  3   56 20.239 12 34.64\n  4   56 13.434 11 16.00\n  5   56 15.102  9 47.35  19.378 0.079  18.039 0.022  17.175 0.009\n  6   56  6.309 10  5.77  15.412 0.018  14.816 0.090  14.445 0.008\n  7   56 22.332  8 26.01                18.261 0.027  17.249 0.009\n  8   56 33.250  9 17.90  16.449 0.019  15.861 0.009  15.471 0.021\n  9   55 52.290 10 15.61                19.964 0.120  18.919 0.019\n\nNOTES: The object referred to as Ref1 by Dierks et al. (GCN Message 17\nDec 1997 and IAUC 6791) is our #2; our measure of R~20.1 is an\nindependent measure from the APM measure and is approximate because of\na poor measure at V and therefore uncertain color correction, but\nnonetheless verifies their measure. We caution that their object Ref2\nis slightly non-stellar in our images and should probably be avoided as\na local calibration source.  Castander et al. (IAUC 6791) report\nR=20.14 +/- 0.02 for our #2.  The source located approximately 26\" SSW\nas noted by Rhodes et al. (GCN Message 17 Dec 1997 and IAUC 6793) is\nalso our #2; their object 26\" NE of the OT is our #1 (they report\nI=15.93 and 18.46 for #1 and #2, respectively); their object 55\" NW is\nour #3.\n\nWe plan to obtain further calibrated VR and I measures in this field,\nweather permitting, in the coming months.  A finding chart showing\nthese local \"standards\" is posted on our ftp site at\n\n        ftp.nofs.navy.mil  (192.68.148.67)\n\nas file /pub/outgoing/fjv/grb971214/locstds.ps.gz.  We will update the\nphotometric measures as we obtain and reduce more data, and will keep\nthe latest data in the file /pub/outgoing/fjv/grb971214/locstds.dat.  We\nencourage observers to consult this file to put their measures on a\nstandard system.\n\nThis message is quotable in publications.\n\nC.B. Luginbuhl; cbl@nofs.navy.mil",
  "format": "text/plain",
  "submitter": "Arne A Henden at USNO/USRA <aah@nofs.navy.mil>",
  "email": "circulars@gcn.nasa.gov",
  "createdOn": 882921600000,
  "editedOn": 1721067933107,
  "subject": "GRB971214: Optical Observations and Calibrations ",
  "bibcode": "1997GCN....16....1H",
  "version": 2
}