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Title: Rotation of the optical polarization angle associated with the 2008 γ-ray flare of blazar W Comae

An R-band photopolarimetric variability analysis of the TeV bright blazar W Comae between 2008 February 28 and 2013 May 17 is presented. The source showed a gradual tendency to decrease its mean flux level with a total change of 3 mJy. A maximum and minimum brightness states in the R band of 14.25 ± 0.04 and 16.52 ± 0.1 mag, respectively, were observed, corresponding to a maximum variation of ΔF = 5.40 mJy. We estimated a minimum variability timescale of Δt = 3.3 days. A maximum polarization degree P = 33.8% ± 1.6%, with a maximum variation of ΔP = 33.2%, was found. One of our main results is the detection of a large rotation of the polarization angle from 78° to 315° (Δθ ∼ 237°) that coincides in time with the γ-ray flare observed in 2008 June. This result indicates that both optical and γ-ray emission regions could be co-spatial. During this flare, a correlation between the R-band flux and polarization degree was found with a correlation coefficient of r {sub F} {sub –} {sub p} = 0.93 ± 0.11. From the Stokes parameters, we infer the existence of two optically thin synchrotron components that contribute to the polarizedmore » flux. One of them is stable with a constant polarization degree of 11%. Assuming a shock-in jet model during the 2008 flare, we estimated a maximum Doppler factor δ {sub D} ∼ 27 and a minimum of δ {sub D} ∼ 16; a minimum viewing angle of the jet ∼2.°0; and a magnetic field B ∼ 0.12 G.« less
Authors:
; ;  [1] ; ;  [2] ;  [3]
  1. Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. 70-264, Mexico D.F., 04510 (Mexico)
  2. Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. 810, Ensenada, B.C., 22800 (Mexico)
  3. Instituto Nacional de Astrofísica, Óptica y Electrónica, Apdo. Postal 51 y 216, 72000 Tonantzintla, Puebla (Mexico)
Publication Date:
OSTI Identifier:
22370490
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 794; 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; BRIGHTNESS; CORRELATIONS; DETECTION; DOPPLER EFFECT; EMISSION; GALAXIES; GAMMA RADIATION; JET MODEL; MAGNETIC FIELDS; PHOTOMETRY; POLARIZATION; ROTATION; STELLAR FLARES; STOKES PARAMETERS; SYNCHROTRON RADIATION; TEV RANGE