{
  "bibcode": "2003GCN..2144....1E",
  "body": "Y.Efimov, K.Antoniuk, V.Rumyantsev (CrAO) and A.Pozanenko (IKI)   report:\n\nWe  have  performed  linear  polarization  observations  of   the optical\ncounterpart to GRB030329 (Peterson and Price, GCN  1985; Torii,  GCN   1986)\nand   a  reference   star   (RA=161.153362, Decl=+21.449663,  Henden,  GCN\n2082)  with 125 cm reflector (AZT-11) equipped with  double  beams  UBVRI\npolarimeter. The observations  were done on March 29 between 0.76689 and\n0.9230 UT (JD2452728.2669  - 2452728.4230)  at  moderate  sky  condition and\nsometimes  variable  transparency.  Also the reference star appears to be an\neclipsing binary (J. Fitzgerald & J. Orosz, GCN 2056, 2070). However it can\nbe considered as a  reference star with a sufficient  accuracy because of\nboth the simultaneous observation of the star by V.Rumyantsev et al. (GCN\n2005) with accuracy better than 0.02mag @ 180 s and orbital period\nestimation (GCN  2070) show that the star was far from eclipsing phase.\n\nThe preliminary analysis of UBVRI photometric data shows no significant\ncolor variability of the OT, which is in agreement with the prediction of\ncolor behavior for \"standard\" afterglow models. More detailed analysis is in\nprogress.\n\nPolarization measurements were corrected for instrumental effects. The\nweighted mean  of  reported  polarization  degree and position angles are\nderived from the normalized Stokes parameters. The data obtained for OT and\nreference star are presented below. Indicated in the table are: fractions of\nJulian Day JD-2452827, filter, polarization parameters (degree P and\nposition angle PA), their mean errors ME, and the duration DT of\nmeasurements in minutes.\n\nWe found that the polarization in R filter may be considered as marginally\ndetected.  The interstellar polarization in the direction of GRB 030329 is\nless then 0.2% according to interstellar polarization data at high  galactic\nlatitude reported by  Berdyugin et al. (2001,A&A, 372,  276).  The\npolarization of the reference star combined from measurements in two nights\n(29 and 30 March, 2003) significantly differs from that found for OT of\nGRB030329.\n\nMid time, (GRB 30329) Date: March, 29, 2003\n  JD-2452729 FILTER  P (%)  ME    PA    ME   DT\n\n   0.3261    R       0.90   0.39  109   12   86\n\n(Reference star), Combined data March, 29-30, 2003\n  FILTER   P      ME     PA      ME      DT\n\n    R      0.33   0.17   174.2   13.7\n\nDetailed polarization analysis in all UBVRI filters is in progress.",
  "circularId": 2144,
  "createdOn": 1050576424000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB030329, UBVRI polarimetry, R-polarization",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 030329"
}