The RoboPol optical polarization survey of gamma-ray-loud blazars

Pavlidou, V.; Angelakis, E.; Myserlis, I.; Blinov, D.; King, O. G.; Papadakis, I. E.; Tassis, Konstantinos; Hovatta, T.; Pazderska, B.; Paleologou, E. V.; Baloković, Mislav; Feiler, R.; Fuhrmann, L.; Khodade, P.; Kus, A. J.; Kylafis, N. D.; Modi, Deepa; Panopoulou, G. V.; Papamastorakis, I.; Pazderski, E.; Pearson, T. J.; Rajarshi, C.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Zensus, J. A.

doi:10.1093/mnras/stu904

Cited by 67 publications

(98 citation statements)

References 26 publications

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“…We calculate the duty cycle in our sample in the same way as they do by taking the first observation of each source and calculating the fraction of sources that have polarization fraction > 4%. In the calculation of the duty cycle, we account for the Ricean bias and de-bias our polarization fraction observations similarly as in Pavlidou et al (2014). Accounting for the uncertainties in the measurements, we find the duty cycle in our TeV objects to be 59 +6.9 −15.1 % and in the non-TeV sources 74 +15.8 −21.1 %, which are consistent with each other within uncertainties.…”

Section: Fraction Of Polarized Sources and The Duty Cycle Of High Polsupporting

confidence: 73%

Optical polarization of high-energy BL Lacertae objects

Hovatta

Lindfors

Blinov

et al. 2016

A&A

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Context. We investigate the optical polarization properties of high-energy BL Lac objects using data from the RoboPol blazar monitoring program and the Nordic Optical Telescope. Aims. We wish to understand if there are differences in the BL Lac objects that are detected with the current-generation TeV instruments compared to those that have not yet been detected. Methods. We use a maximum likelihood method to investigate the optical polarization fraction and its variability in these sources. In order to study the polarization position angle variability, we calculate the time derivative of the electric vector position angle (EVPA) change. We also study the spread in the Stokes Q/I − U/I-plane and rotations in the polarization plane. Results. The mean polarization fraction of the TeV-detected BL Lacs is 5% while the non-TeV sources show a higher mean polarization fraction of 7%. This difference in polarization fraction disappears when the dilution by the unpolarized light of the host galaxy is accounted for. The TeV sources show somewhat lower fractional polarization variability amplitudes than the non-TeV sources. Also the fraction of sources with a smaller spread in the Q/I − U/I-plane and a clumped distribution of points away from the origin, possibly indicating a preferred polarization angle, is larger in the TeV than in the non-TeV sources. These differences between TeV and non-TeV samples seems to arise from differences between intermediate and high spectral peaking sources instead of the TeV detection. When the EVPA variations are studied, the rate of EVPA change is similar in both samples. We detect significant EVPA rotations in both TeV and non-TeV sources, showing that rotations can occur in high spectral peaking BL Lac objects when the monitoring cadence is dense enough. Our simulations show that we cannot exclude a random walk origin for these rotations. Conclusions. These results indicate that there are no intrinsic differences in the polarization properties of the TeV-detected and nonTeV-detected high-energy BL Lac objects. This suggests that the polarization properties are not directly related to the TeV-detection, but instead the TeV loudness is connected to the general flaring activity, redshift, and the synchrotron peak location.

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Section: Fraction Of Polarized Sources and The Duty Cycle Of High Polsupporting

confidence: 73%

Optical polarization of high-energy BL Lacertae objects

Hovatta

Lindfors

Blinov

et al. 2016

A&A

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“…An additional 105 AGNs are members of either the precursor survey to MOJAVE (the 2cm VLBA survey; Kellermann et al 1998), the low-luminosity MOJAVE AGN sample (Lister et al 2013), the 3rd EGRET γ-ray catalog (Hartman et al 1999), the 3FGL Fermi LAT γ-ray catalog (Acero et al 2015), or the ROBOPOL optical polarization monitoring sample (Pavlidou et al 2014). Finally, we have included 13 AGNs that were originally candidates for the above samples, but did not meet the final selection criteria.…”

Section: Sample Selectionmentioning

confidence: 99%

MOJAVE. XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-scale AGN Jets from 1996 to 2017

Lister

Aller

et al. 2018

ApJS

279

234

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We present 5321 milliarcsecond-resolution total intensity and linear polarization maps of 437 active galactic nuclei (AGNs) obtained with the VLBA at 15 GHz as part of the MOJAVE survey, and also from the NRAO data archive. The former is a long-term program to study the structure and evolution of powerful parsec-scale outflows associated with AGNs. The targeted AGNs are drawn from several flux-limited radio and γ-ray samples, and all have correlated VLBA flux densities greater than ∼ 50 mJy at 15 GHz. Approximately 80% of these AGNs are associated with γ-ray sources detected by the Fermi LAT instrument. The vast majority were observed with the VLBA on 5 to 15 occasions between 1996 January 19 and 2016 December 26, at intervals ranging from a month to several years, with the most typical sampling interval being six months. A detailed analysis of the linear and circular polarization evolution of these AGN jets are presented in other papers in this series.

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“…Since 2013 RoboPol has been monitoring the optical linear polarisation of a sample of 60 blazars including 47 F-GAMMA sources. First polarisation results of RoboPol are presented in Pavlidou et al (2014); Blinov et al (2015Blinov et al ( , 2016.…”

Section: Other Facilitiesmentioning

confidence: 99%

The F-GAMMA programme: multi-frequency study of active galactic nuclei in theFermiera

Fuhrmann

Angelakis

Zensus

et al. 2016

A&A

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Context. To fully exploit the scientific potential of the Fermi mission for AGN physics, we initiated the F-GAMMA program. Between 2007 and 2015 the F-GAMMA was the prime provider of complementary multi-frequency monitoring in the radio regime. Aims. We quantify the radio variability of γ-ray blazars. We investigate its dependence on source class and examine whether the radio variability is related to the γ-ray loudness. Finally, we assess the validity of a putative correlation between the two bands. Methods. The F-GAMMA monitored monthly a sample of about 60 sources at up to twelve radio frequencies between 2.64 and 228.39 GHz. We perform a time series analysis on the first 2.5-year dataset to obtain variability parameters. A maximum likelihood analysis is used to assess the significance of a correlation between radio and γ-ray fluxes.Results. We present light curves and spectra (coherent within ten days) obtained with the Effelsberg 100-m and IRAM 30-m telescopes. All sources are variable across all frequency bands with amplitudes increasing with frequency up to rest frame frequencies of around 60-80 GHz as expected by shock-in-jet models. Compared to FSRQs, BL Lacs show systematically lower variability amplitudes, brightness temperatures and Doppler factors at lower frequencies, while the difference vanishes towards higher ones. The time scales appear similar for the two classes. The distribution of spectral indices appears flatter or more inverted at higher frequencies for BL Lacs. Evolving synchrotron self-absorbed components can naturally account for the observed spectral variability. We find that the Fermi-detected sources show larger variability amplitudes as well as brightness temperatures and Doppler factors, than non-detected ones. Flux densities at 86.2 and 142.3 GHz correlate with 1 GeV fluxes at a significance level better than 3σ, implying that γ rays are produced very close to the mm-band emission region.

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The RoboPol optical polarization survey of gamma-ray-loud blazars

Cited by 67 publications

References 26 publications

Optical polarization of high-energy BL Lacertae objects

Optical polarization of high-energy BL Lacertae objects

MOJAVE. XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-scale AGN Jets from 1996 to 2017

The F-GAMMA programme: multi-frequency study of active galactic nuclei in theFermiera

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