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The RINGO2 and DIPOL optical polarization catalogue of blazars

Jermak, HE and Steele, IA and Lindfors, E and Hovatta, T and Nilsson, K and Lamb, GP and Mundell, CG and Barres de Almeida, U and Berdyugin, A and Kadenius, V and Reinthal, R and Takalo, L (2016) The RINGO2 and DIPOL optical polarization catalogue of blazars. Monthly Notices of the Royal Astronomical Society, 462 (4). pp. 4267-4299. ISSN 0035-8711

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Abstract

We present ∼2000 polarimetric and ∼3000 photometric observations of 15 γ-ray bright blazars over a period of 936 days (2008-10-11 to 2012-10-26) using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT) and Fermi-LAT γ-ray data). In 11 out of 15 sources we identify a total of 19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We group the sources into subclasses based on their broad-band spectral characteristics and compare their observed optical and γ-ray properties. We find that (1) the optical magnitude and γ-ray flux are positively correlated, (2) EVPA rotations can occur in any blazar subclass, four sources show rotations that go in one direction and immediately rotate back, (3) we see no difference in the γ-ray flaring rates in the sample; flares can occur during and outside of rotations with no preference for this behaviour, (4) the average degree of polarization (DoP), optical magnitude and γ-ray flux are lower during an EVPA rotation compared with during non-rotation and the distribution of the DoP during EVPA rotations is not drawn from the same parent sample as the distribution outside rotations, (5) the number of observed flaring events and optical polarization rotations are correlated, however we find no strong evidence for a temporal association between individual flares and rotations and (6) the maximum observed DoP increases from ∼10 per cent to ∼30 per cent to ∼40 per cent for subclasses with synchrotron peaks at high, intermediate and low frequencies, respectively.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 19 Jan 2017 10:48
Last Modified: 07 Sep 2017 22:15
DOI or Identification number: 10.1093/mnras/stw1770
URI: http://researchonline.ljmu.ac.uk/id/eprint/5301

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