Blazar Optical Polarimetry: Current Progress in Observations and Theories

Zhang, Haocheng

doi:10.3390/galaxies7040085

Cited by 27 publications

(14 citation statements)

References 103 publications

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“…This can lead to overall similar radiation signatures as in the striped jet model. Additional constraints through, for instance, polarization signatures, may help to distinguish these models (Zhang 2019;Zhang et al 2020).…”

Section: Summary and Discussionmentioning

confidence: 99%

Radiation Signatures From Striped Blazar Jet

Zhang,

Giannios

2020

Preprint

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Relativistic jets from supermassive black holes are among the most powerful and luminous astrophysical systems in Universe. We propose that the open magnetic field lines through the black hole, which drive a strongly magnetized jet, may have their polarity reversing over time scales related to the growth of the magneto-rotational dynamo in the disc, resulting in dissipative structures in the jet characterized by reversing toroidal field polarities, referred to as "stripes". Magnetic reconnection between the stripes dissipates the magnetic energy and powers jet acceleration. The striped jet model can explain the jet acceleration, large-scale jet emission, and blazar emission signatures consistently in a unified physical picture. Specifically, we find that the jet accelerates to the bulk Lorentz factor Γ 10 within one parsec distance from the central engine. The acceleration slows down but continues at larger distances, with intrinsic acceleration rate Γ/Γ between 0.0005 yr −1 and 0.005 yr −1 at tens of parsecs, which is in very good agreement with recent radio observations. Magnetic reconnection continuously accelerates nonthermal particles over large distances from the central engine, resulting in the core-shift effect and overall flat-to-inverted synchrotron spectrum. The large-scale spectral luminosity peak 𝜈 peak is anti-proportional to the location of the peak of the dissipation, which is set by the minimal stripe width 𝑙 min . The blazar zone is approximately at the same location. At this distance, the jet is moderately magnetized, with the comoving magnetic field strength and dissipation power consistent with typical leptonic blazar model parameters.

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Section: Summary and Discussionmentioning

confidence: 99%

Radiation Signatures From Striped Blazar Jet

Zhang,

Giannios

2020

Preprint

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“…The detection of polarized emission has been considered the incontrovertible proof that the synchrotron emission dominates in the optical part of the spectrum of blazars (e.g., Itoh et al 2016;Zhang 2019). Polarization as high as 10 per cent and 36 per cent has been detected in the γ-ray-emitting NLSy1 SBS 0846+513 (Maune et al 2014) and PMN J0948+0022 (Itoh et al 2013) accompanied by intraday variation in the photometric light curves.…”

Section: Source Namementioning

confidence: 98%

Short time-scale variability of $γ$-ray-emitting narrow-line Seyfert 1 galaxies in optical and UV bands

D'Ammando

2020

Preprint

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We report the first systematic analysis of single exposures of all optical and ultraviolet (UV) observations performed by the UltraViolet and Optical Telescope (UVOT) on board the Neil Gehrels Swift Observatory satellite available up to 2019 April of six γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). Rapid variability has been significantly detected on hours time-scale for 1H 0323+342, SBS 0846+513, PMN J0948+0022, and PKS 2004-447 in 18 observations for a total of 34 events. In particular, we report the first detection of significant variability on short time-scale (3-6 ks) in optical for PKS 2004-447, and UV for 1H 0323+342 and PMN J0948+0022. The shortest variability time-scale observed for 1H 0323+342, SBS 0846+513, PMN J0948+0022, and PKS 2004-447 (assuming a Doppler factor δ = 10) gives a lower limit on the size of emission region between 9.7×10 14 (for SBS 0846+513) and 1.6×10 15 cm (for 1H 0323+342), suggesting that the optical and UV emission during these events is produced in compact regions within the jet. These observations provide unambiguous evidence about the relativistically beamed synchrotron emission in these sources, similar to blazars. A remarkable variability has been observed for PMN J0948+0022 on 2009 June 23 with an increase from ∼1.1 to 0.4 mag going from v to w2 filter in ∼1.6 h and a decrease at the initial level in a comparable time. The higher fractional flux change observed for this and other events at lower frequencies suggests that the synchrotron emission is more contaminated by thermal emission from accretion disc at higher frequencies.

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“…For an updated review of optical polarization in AGN jets, see [206] in this special issue. Variability in the optical polarization can also be used to put constraints on the geometry of the emitting regions, and in particular on the relative role of the small plasmoid (the single-zone that emits from optical to gamma-rays) and the larger jet [207,208].…”

Section: Polarization Signaturesmentioning

confidence: 99%

Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets

Cerruti

2020

Galaxies

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Supermassive black holes lying in the center of galaxies can launch relativistic jets of plasma along their polar axis. The physics of black-hole jets is a very active research topic in astrophysics, owing to the fact that many questions remain open on the physical mechanisms of jet launching, of particle acceleration in the jet, and on the radiative processes. In this work I focus on the last item, and present a review of the current understanding of radiative emission processes in supermassive-black-hole jets.

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Blazar Optical Polarimetry: Current Progress in Observations and Theories

Cited by 27 publications

References 103 publications

Radiation Signatures From Striped Blazar Jet

Radiation Signatures From Striped Blazar Jet

Short time-scale variability of $γ$-ray-emitting narrow-line Seyfert 1 galaxies in optical and UV bands

Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets

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