Time correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission

Max-Moerbeck, W.; Hovatta, T.; Richards, J. L.; King, O. G.; Pearson, T. J.; Readhead, A. C. S.; Reeves, R.; Shepherd, M. C.; Stevenson, M. A.; Angelakis, E.; Fuhrmann, L.; Grainge, Keith; Pavlidou, V.; Romani, Roger W.; Zensus, J. A.

doi:10.1093/mnras/stu1749

Cited by 138 publications

(134 citation statements)

References 47 publications

(44 reference statements)

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“…This arises from the low fraction (7%) of gamma-ray loud sources in the radio-weak sample (Figure 11, right), as compared to the higher 50% fraction of gamma-ray loud sources in the radio-strong sample (Figure 11, middle), as expected due to the known radio-gammaray flux correlation in blazars (e.g. Ackermann et al 2011a;Max-Moerbeck et al 2014). This selection bias, combined with the significantly higher m5 of radio-weak sources relative to the radio-strong sources (Section 5.1), dilutes the relationship between m5 and gamma-ray loudness clearly seen when they are separated by flux density.…”

Section: Gamma-ray Loudnessmentioning

confidence: 63%

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

Koay

Macquart

Jauncey

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We investigate the relationship between 5 GHz interstellar scintillation (ISS) and 15 GHz intrinsic variability of compact, radio-selected AGNs drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory (OVRO) blazar monitoring program. We discover that the strongest scintillators at 5 GHz (modulation index, m 5 ≥ 0.02) all exhibit strong 15 GHz intrinsic variability (m 15 ≥ 0.1). This relationship can be attributed mainly to the mutual dependence of intrinsic variability and ISS amplitudes on radio core compactness at ∼ 100 µas scales, and to a lesser extent, on their mutual dependences on source flux density, arcsec-scale core dominance and redshift. However, not all sources displaying strong intrinsic variations show high amplitude scintillation, since ISS is also strongly dependent on Galactic line-of-sight scattering properties. This observed relationship between intrinsic variability and ISS highlights the importance of optimizing the observing frequency, cadence, timespan and sky coverage of future radio variability surveys, such that these two effects can be better distinguished to study the underlying physics. For the full MASIV sample, we find that Fermi-detected gamma-ray loud sources exhibit significantly higher 5 GHz ISS amplitudes than gamma-ray quiet sources. This relationship is weaker than the known correlation between gamma-ray loudness and the 15 GHz variability amplitudes, most likely due to jet opacity effects.

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Section: Gamma-ray Loudnessmentioning

confidence: 63%

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

Koay

Macquart

Jauncey

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…From that combination it follows that the γ-ray emission region is best constrained to a distance of (1.9 ± 1.1) pc away from the jet base. In a similar study, Max-Moerbeck et al (2014) obtain a time lag of (−40 ± 13) d between the leading γ rays and the lagging 15 GHz radio emission. Following their reasoning, this time lag translates into a relative distance of (2 ± 1) pc between the 15 GHz unit-opacity surface and the γ-ray site.…”

Section: Localizing the γ-Ray Emissionmentioning

confidence: 67%

What can the 2008/10 broadband flare of PKS 1502+106 tell us?

Karamanavis

Fuhrmann

Angelakis

et al. 2016

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Context. The origin of blazar variability, as seen from radio up to γ rays, is still a heavily debated matter, and broadband flares offer a unique testbed for developing a better understanding of these extreme objects. One of these energetic outbursts was detected by Fermi/LAT in 2008 from the blazar PKS 1502+106. The outburst was observed from γ rays down to radio frequencies. Aims. Through the delay between flare maxima at different radio frequencies, we study the frequency-dependent position of the unitopacity surface and infer its absolute position with respect to the jet base. This nuclear opacity profile enables the jet's magnetic field tomography. We also localize the γ-ray emission region and explore the flare production mechanism. Methods. The PKS 1502+106 radio flare is studied through single-dish flux density measurements at 12 frequencies in the range 2.64 to 226.5 GHz. To quantify the flare, we employ both a Gaussian process regression and a discrete cross-correlation function analysis. Results. We find that the light curve parameters (flare amplitude and cross-band delays) show a power-law dependence on frequency. Delays decrease with frequency, and the flare amplitudes increase up to about 43 GHz, and then decay. This behavior is consistent with the propagation of a shock downstream in the jet. The self-absorbed radio cores are located between approximately ten and four pc from the jet base, and their magnetic field strengths range between 14 and 176 mG, at the frequencies 2.64 to 86.24 GHz. Finally, the γ-ray active region is located at (1.9 ± 1.1) pc away from the jet base.

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“…Note that in Figure 14 we show the light curves on a logarithmic scale with a fixed dynamic range in order to facilitate direct comparison with Figure 7; on a linear plot both the γ-ray and the radio flare appear strikingly peaked. Based on the statistical properties of Fermi-LAT and OVRO 15GHz light curves, Max-Moerbeck et al (2014) have shown that the γ-ray and the radio flare are likely causally related. During most of the flaring activity in 2012, Mrk 421 was very close to the Sun on the sky, which resulted in relatively poor multiwavelength coverage.…”

Section: Brief Summary Of the Flaring Activity In 2012mentioning

confidence: 99%

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

Baloković¹,

Paneque²,

Madejski³

et al. 2016

ApJ

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We present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy(VHE) γ-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep 3 G » power law, with no evidence for an exponential cutoff or additional hard components up to ∼80keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure that relates to the two bumps of the broadband SED. In each bump, the variability increases with energy, which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in situ electron acceleration and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states.

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Time correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission

Cited by 138 publications

References 47 publications

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

The MASIV Survey – IV. Relationship between intra-day scintillation and intrinsic variability of radio AGNs

What can the 2008/10 broadband flare of PKS 1502+106 tell us?

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

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