{
  "bibcode": "2002GCN..1596....1R",
  "body": "GRB 021004: polarimetric observations\n---------------------------------------\n\nE. Rol (University of Amsterdam), J.M. Castro Cerón (ROA, San Fernando),\nJ. Gorosabel, A.J. Castro-Tirado (IAA-CSIC, Granada), A. Fruchter (STScI,\nBaltimore), J. Greiner (MPE, Garching), J. Hjorth (Univ. of Copenhagen),\nE. Pian (OAT-INAF, Trieste) R.A.M. Wijers and E. van den Heuvel (Univ.\nof Amsterdam), on behalf of GRACE, report:\n\n\n\"We have performed polarimetric observations of the afterglow of\nGRB 021004 (Fox, GCN 1564; Shirasaki et al. GCN 1565) with the FORS1\ninstrument at the VLT. The observations were done between October 5.15\nand October 5.20 UT in the V-band.\n   Independently of Covino et al. (GCN 1595), we find a polarization value\nfor the OT of P = (1.32 +/- 0.28) %, with a position angle of theta =\n(125 +/- 1) degrees.\n   Correcting for possible polarization due to the interstellar medium is\nrather difficult, since there are few bright stars close to the OT position.\nUsing 12 bright stars within 4.5 arcmin from this position, we find a mean\nISM polarization of P = (0.7 +/- 0.3) % and theta = (116 +/- 4) degrees.\nThe error in the degree of polarization is obtained from the spread in the\nvalues found for the field stars.\n   The resultant degree of polarization for the OT is P = (0.57 +/- 0.40) %.\nSince this result could be entirely due to polarization induced by ISM,\nwe derive a 3-sigma upper limit of P = 1.2 % for the degree of\npolarization.\n   The QU Stokes' parameter plane can be seen at:\n http://zon.wins.uva.nl/~evert/grb021004/\n\nThis note can be cited.\"",
  "circularId": 1596,
  "email": "ajct@iaa.es",
  "subject": "GRB 021004: polarimetric observations",
  "format": "text/plain",
  "version": 2,
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "submitter": "Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>",
  "editedOn": 1731775277066,
  "createdOn": 1033994519000,
  "eventId": "GRB 021004"
}