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Title: ANTI-CORRELATED OPTICAL FLUX AND POLARIZATION VARIABILITY IN BL LAC

We present the results of photometric (V band) and polarimetric observations of the blazar BL Lac during 2008-2010 using TRISPEC attached to the KANATA 1.5 m telescope in Japan. The data reveal a great deal of variability ranging from days to months with detection of strong variations in fractional polarization. The V band flux strongly anticorrelates with the degree of polarization during the first of two observing seasons but not during the second. The direction of the electric vector, however, remained roughly constant during all of our observations. These results are consistent with a model with at least two emission regions being present, with the more variable component having a polarization direction nearly perpendicular to that of the relatively quiescent region so that a rising flux can produce a decline in degree of polarization. We also computed models involving helical jet structures and single transverse shocks in jets and show that they might also be able to agree with the anticorrelations between flux and fractional polarization.
Authors:
 [1] ;  [2] ;  [3] ; ; ;  [4]
  1. Inter-University Centre for Astronomy and Astrophysics (IUCAA), Ganeshkhind, Pune 411 007 (India)
  2. Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263 129 (India)
  3. Department of Physics, The College of New Jersey, P.O. Box 7718, Ewing, NJ 08628-0718 (United States)
  4. Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan)
Publication Date:
OSTI Identifier:
22364037
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BL LACERTAE OBJECTS; DETECTION; EMISSION; GALAXIES; JAPAN; JETS; PHOTOMETRY; POLARIZATION; TELESCOPES; VARIATIONS; VECTORS