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REVIEW 4 major objections 5 minor 28 references

FACT -- Multi-wavelength analysis of more than 30 flares of Mrk 421

T0 review · 4 major / 5 minor · reviewed 2026-08-14 · deepseek-v4-flash

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Pith's one-line read The paper shows that Mrk 421's TeV and X-ray flares are simultaneous to within about a quarter day, and that its 15 GHz radio light curve is a delayed, smeared echo of its GeV light curve arriving about 43 days later.

desk verdict A useful observational core on Mrk 421's TeV/X-ray connection, but the GeV-to-radio response claim is a fit, not a prediction, and needs uncertainties or an out-of-sample test. read the letter →

arxiv 1908.09770 v1 pith:WG3IKNRP submitted 2019-08-26 astro-ph.HE

Vitalii Sliusar , Axel Arbet-Engels , Dominik Baack , Matteo Balbo , Adrian Biland , Michael Blank , Tomas Bretz , Kai Bruegge
show 17 more authors
Michael Bulinski Jens Buss Manuel Doerr Daniela Dorner Dominik Elsaesser Dorothee Hildebrand Karl Mannheim Sebastian mueller Dominik Neise Maximilian Noethe Aleksander Paravac Wolfgang Rhode Bernd Schleicher Kevin Sedlaczek Amit Shukla Roland Walter Elan von Willert
This is my paper · ORCID
classification astro-ph.HE
keywords blazarvariabilityMrk421multi-wavelengthlightcurvesTeV/X-raycorrelationGeV-to-radiodelaysynchrotronself-ComptonemissionBayesianblocksconicaljet
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

Using 5.5 years of nearly continuous observations from radio to TeV energies, the paper identifies more than 30 individual flares of the blazar Mrk 421, an active galaxy whose jet points nearly toward Earth, and compares them across bands. Its central finding is that the TeV and X-ray light curves are strongly correlated with no significant lag, $(0.26 \pm 0.46)$ days, with 95% of short flares appearing in both bands. Its second finding is that the 15 GHz radio light curve can be reconstructed by convolving the GeV light curve with a fast-rise, slow-decay response profile delayed by about 43 days. Together these results argue that the high-energy variability is governed by two independent parameters, overall amplitude and cutoff energy, and that the radio emission is a delayed downstream echo of GeV-emitting activity.

What carries the argument

The machinery is the flaring light-curve sample itself: more than 30 flares picked out by the Bayesian Block algorithm, a change-point analysis that splits each light curve into statistically significant flux states, from TeV, GeV, and X-ray light curves assembled over 5.5 years. Two analytic devices carry the argument: the discrete correlation function, used to measure lags and correlations between irregularly sampled light curves, and a convolution of the GeV light curve with a two-component response profile, defined by rise time, fall time, and two spectral indices, plus an overall delay. That convolution converts the observed GeV-to-radio correlation into a concrete echo model, so it is the load-bearing step that turns a statistical association into a physical transfer function.

What would settle it

Take an isolated GeV flare with no neighboring activity and monitor the 15 GHz radio band daily for the next 60 days. The model predicts a radio bump that rises on a roughly 3-day timescale and decays on a roughly 7.7-day timescale, peaking about 43 days after the GeV flare; if no such bump appears, or if the delay changes from flare to flare, the single-template convolution claim is refuted.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that Mrk 421's multi-wavelength variability is organized by two distinct lag structures. TeV and X-ray flares rise and decay over a few days and are coincident at zero lag, with a combined lag of $(0.26 \pm 0.46)$ days and 95% of short flares shared between bands; the paper reads this as a single electron population driven by one parameter, the cutoff energy. Meanwhile the GeV light curve, convolved with a response profile having rise time $t_{\rm rise}=3$ days, fall time $t_{\rm fall}=7.7$ days, and spectral indices $\rho(\nu)=1.36$ and $\phi(\nu)=0.36$, plus a 43-day delay, reproduces the observed 15 GHz radio light curve with $\chi^2_\nu = 1.2$. The paper concludes that the blazar's variability is controlled by two independent parameters, amplitude and cutoff energy, and that proton-synchrotron or other hadronic mechanisms cannot account for the observed X-ray/TeV simultaneity.

Load-bearing premise

The radio-reproduction claim rests on the assumption that one fixed response shape, borrowed from modeling another source's flares, together with a 43-day delay, correctly describes how Mrk 421's GeV flares are transferred into the radio; if the radio variability is generated independently, the claimed GeV-to-radio echo loses its support.

Editorial extensions

If this is right

  • If the TeV and X-ray bands respond at zero lag, the radiating electrons must cool and radiate on sub-day timescales, which rules out proton-synchrotron emission as the dominant TeV mechanism.
  • If the radio light curve is a delayed convolution of the GeV light curve, then radio variations are not an independent component but the delayed, broadened signature of GeV activity, consistent with a shock moving outward and becoming transparent to radio later.
  • If variability is controlled by amplitude and cutoff energy, then no one-zone, one-parameter model can describe the broadband behavior of Mrk 421; models must allow both parameters to vary from flare to flare.
  • The existence of flares seen only in GeV and only in TeV implies that more than one particle population with different spectral shapes contributes to the gamma-ray emission.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • Because the 43-day delay is read from a broad 40-70 day correlation peak, a natural extension is to fit the response model on isolated GeV flares and test whether the delay is actually constant from flare to flare.
  • The same convolution approach could be applied to other bright blazars with continuous GeV and radio monitoring; if the inferred delay scales with jet power or black-hole mass, that would support the propagating-shock picture beyond this one source.
  • The claim that cutoff energy drives variability predicts that X-ray and TeV spectral hardness should track the rise and decay of each flare; a spectral-timing analysis of the same light curves could test that prediction.
  • The GeV-only flares may point to a distinct emission component whose physical nature is not constrained by light curves alone; simultaneous GeV spectra during such flares would be needed to separate it from the dominant electron population.
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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 5 minor

Summary. The paper analyzes 5.5 years of multi-wavelength light curves of the blazar Mrk 421, combining FACT TeV data with Fermi LAT GeV, Swift BAT/XRT, MAXI, UVOT, optical, and OVRO 15 GHz radio data. It reports (1) a strong TeV-X-ray correlation at zero lag, with a combined lag of (0.26 ± 0.46) days (1σ) and 95% of short X-ray and TeV flares coincident based on Bayesian-block flare identification; (2) that the OVRO radio light curve can be reproduced by convolving the Fermi GeV light curve with a fast-rise, slow-decay response profile from Türler et al. (1999), with best-fit parameters t_rise=3 d, t_fall=7.7 d, ρ=1.36, φ=0.36, and an added delay of 43 days, yielding χ²ν=1.2. The paper interprets these results as evidence that the TeV/X-ray variability is dominated by changes in the electron cutoff energy, while the GeV-to-radio connection supports a shock propagating in a conical jet.

Significance. If the TeV-X-ray zero-lag correlation and the accompanying flare catalog are taken as the main observational contribution, the paper provides a useful, long-term, unbiased monitoring result for Mrk 421. The Monte Carlo based lag uncertainty for the TeV-X-ray DCF and the Bayesian-block flare identifications are positive features, and the public multi-wavelength dataset is valuable. The claimed GeV-to-radio reproduction, however, would be an important physical result if established, but as presented it is not an independent prediction: the response parameters and delay are fit to the same radio data that the model is then said to reproduce. The paper's physical conclusions about a propagating shock and about a two-parameter variability description rest substantially on this unsecured claim.

major comments (4)
  1. [Section 3.3] The synthetic radio light curve is constructed by convolving the GeV light curve with the response profile of Section 3.2 of [25], using t_rise, t_fall, ρ, φ, and an additional delay Δt=43 d. These five parameters are adjusted to match the OVRO 15 GHz data, and the quoted χ²ν=1.2 is therefore a goodness-of-fit statistic, not evidence that the model independently reproduces the radio variability. No parameter uncertainties, number of degrees of freedom, treatment of OVRO measurement errors, or synthetic sampling procedure are given, so the fit quality cannot be assessed. An out-of-sample test (e.g., fitting the first half of the light curve and predicting the second half) or an explicit alternative model comparison (e.g., direct delayed radio response with independent variability) is required before conclusion 2 in Section 4 can be drawn.
  2. [Section 3.2 and 3.3] The 40–70 day DCF peak between GeV and radio is broad and both input light curves are strongly autocorrelated, so this peak does not uniquely determine the 43-day delay used in the convolution. The paper reports Monte Carlo lag uncertainties for the TeV-X-ray correlation but does not provide a comparable lag distribution or uncertainty for the GeV-radio DCF. Without an uncertainty on the delay, the specific value Δt=43 d and the physical interpretation of a delayed shock propagation in Section 4 are not quantitatively supported.
  3. [Section 4] The conclusion that the observed variability is controlled by two independent parameters, the amplitude and the cutoff energy, is not directly tested by the presented analysis. The fractional-variability humps and TeV-X-ray zero-lag correlation are consistent with such a picture, but the paper does not show spectral variability measurements (e.g., hardness-intensity diagrams, evolution of the synchrotron peak or cutoff energy) that would demonstrate that the cutoff energy is the second parameter. As written, this is an interpretive leap rather than a derived result.
  4. [Section 3.3] The text notes that the synthetic radio light curve reproduces the data 'except a fast radio flare near MJD 56897.' This is a resolved, months-long feature in the OVRO data, and the model's failure to reproduce it is a substantive exception that is mentioned only in passing. The exception should be quantified (e.g., residual amplitude, significance relative to the fit) and discussed, because a single strong flare that the convolution cannot reproduce weakens the claim that the GeV light curve drives all of the radio variability.
minor comments (5)
  1. [Section 4] The text states that 95% of the short X-ray and TeV flares are coincident, but Table 1 lists 31 TeV flares (18 in TeV+GeV+X-rays, 11 in TeV+X-rays, and 2 TeV-only), of which 29 also appear in X-rays, i.e., 93.5%. The quoted 95% is not directly supported by the table.
  2. [Section 3.2] The Monte Carlo procedure for the lag uncertainties is described only briefly as 'standard deviation of the distribution of the lags obtained for the random subsets.' More detail is needed on how the random subsets are drawn, how many are used, and how the DCF peak is selected, especially because the paper relies on these uncertainties for the headline TeV-X-ray lag.
  3. [Figure 3] The top and bottom panels of Figure 3 use different y-axis scales (arbitrary units for the synthetic radio curve, Jy for OVRO), and the synthetic curve is not overlaid with the data or residuals. Showing residuals or at least an overlay would make the quality of the χ²ν=1.2 fit apparent.
  4. [Table 1] The table lists time ranges in MJD but the column header simply says 'Time ranges, MJD'; for readability, a note that these are days since MJD 55000 or similar would help, and a column header or caption should define the start and end of each flare interval.
  5. [Section 3.2] The sentence 'Flares observed from the X-rays to the TeV are narrow enough to be identified individually' is somewhat unclear, since the Bayesian-block definition requires a duration of at least 2 days and a 2σ amplitude threshold; please state this explicitly in the text before referring to 'flares.'

Circularity Check

1 steps flagged · score 6.0 of 10

The zero-lag TeV/X-ray correlation is independent, but the 'reproduction' of the radio light curve is an in-sample convolution fit presented as confirmation of a GeV-driven conical shock.

  1. fitted input called prediction [Section 3.3 ('GeV to radio response'), Fig. 3, and result 2 in Section 4]
    "Due to a strong and wide correlation of GeV and radio light curves, we attempted to reconstruct the radio light curve as a convolution of the GeV one with a response profile ... The response profile is defined by the equations (1) and (2) of section 3.2 of [25]. We find that the profile has trise = 3 days, tfall = 7.7 days, ρ(ν) = 1.36, φ(ν) = 0.36. An additional delay ∆t = 43 days was added ... We can reproduce the radio light curve (χ2ν = 1.2) except a fast radio flare near MJD 56897."

    The synthetic radio curve is constructed by convolving the GeV light curve with a response kernel whose parameters (trise, tfall, ρ, φ, Δt, plus normalization and baseline) are adjusted to the same OVRO 15 GHz data. Reporting that this curve 'reproduces' the radio light curve with χ2ν = 1.2 is therefore an in-sample goodness-of-fit, not an independent confirmation of a GeV-to-radio transfer law: a flexible kernel fitted to the data will track it by construction. The 43-day delay and the conical-shock interpretation are read off from the fitted kernel, so the fit itself cannot validate them. The zero-lag TeV/X-ray result is not affected by this circularity.

full rationale

Most of the paper is a self-contained empirical analysis: the zero-lag TeV/X-ray correlation (DCF, Bayesian blocks, flare coincidences) and the fractional-variability study are derived directly from the observations and do not reduce to model inputs. The TeV/X-ray result is therefore not circular. The self-citations are also not load-bearing: [25] is an external 3C 273 model, and [26] merely provides a precedent for introducing a delay. However, the second headline result is a fitted model presented as a confirmation. Section 3.3 reconstructs the radio light curve as a convolution of the GeV data with a response kernel whose parameters are found or adopted, and then quotes χ2ν = 1.2 as evidence. The synthetic curve in Fig. 3 is not an out-of-sample prediction; it is the output of a fit to the same OVRO data. The good χ2ν therefore reflects in-sample fit quality, and the 43-day delay and conical-shock inference are properties of the fitted kernel rather than independent consequences. This makes the radio-reproduction claim partially circular, warranting a score of 6, while preserving the independence of the TeV/X-ray analysis.

Assumptions & free parameters 6 free parameters · 5 assumptions · 0 invented entities

The central quantitative claims rest on several fitted response parameters (t_rise, t_fall, rho, phi, delay), a hand-chosen Bayesian-block threshold, and the applicability of a 3C273 response parameterization to Mrk 421. Standard time-series tools (DCF, Bayesian blocks, fractional variability) are assumed reliable. No new physical entities are introduced.

free parameters (6)
  • Radio response rise time t_rise = 3 days
    Chosen so the synthetic radio light curve matches OVRO 15 GHz data in Section 3.3; no uncertainty is quoted.
  • Radio response fall time t_fall = 7.7 days
    Second shape parameter of the response profile, fitted to the OVRO radio light curve in Section 3.3; no uncertainty is quoted.
  • Radio response spectral index rho = 1.36
    Parameter of the Türler et al. response profile (Eq. (1)-(2) of [25]), fitted to the OVRO radio light curve.
  • Radio response phase phi = 0.36
    Additional parameter of the response profile from [25], fitted to the OVRO radio light curve.
  • GeV-to-radio delay Delta t = 43 days
    Added to align the synthetic radio curve with the observed one; lies within the wide 40-70 day DCF lag range reported in Section 3.2.
  • Bayesian Block false-positive probability = 5%
    Hand-chosen threshold for declaring flares in Section 3.2; directly affects the flare catalog and the 95% coincidence fraction.
assumptions (5)
  • domain assumption DCF with 1-day bins and Monte Carlo lag uncertainties reliably estimates cross-correlation lags from irregularly sampled multi-band light curves.
    Invoked throughout Section 3.2 to report zero-lag TeV/X-ray and 30-70 day GeV/radio lags; the paper provides only a sketch of the Monte Carlo procedure.
  • ad hoc to paper The Türler et al. (1999) response profile (Eq. (1)-(2) of [25]) describes the GeV-to-radio transfer function of Mrk 421 with a single fixed delay.
    Borrowed from 3C273 modeling and used in Section 3.3 without an independent justification for Mrk 421; the central radio-reproduction claim depends on it.
  • domain assumption FACT TeV and Swift/MAXI X-ray bands trace the same electron population in a one-zone SSC jet, so near-zero lag implies a common driver.
    This is the interpretive bridge in Section 4 between the observed DCF and the conclusion that variability is controlled by cutoff-energy changes.
  • domain assumption The two-hump fractional variability spectrum indicates variability of the cutoff energies of the two SSC components, rather than other mechanisms.
    Section 3.1 and Section 4; this is a plausible model interpretation but is not derived uniquely from the fractional variability values.
  • domain assumption Proton acceleration and cooling timescales in lepto-hadronic models are much longer than the observed TeV-X-ray delay, making proton-synchrotron emission unable to explain the TeV band.
    Section 4 conclusion; no derivation or reference for the timescale comparison is given in this proceedings paper.

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Cite this review

Pith. "Pith review of FACT -- Multi-wavelength analysis of more than 30 flares of Mrk 421." pith.science (2026). https://pith.science/paper/WG3IKNRP

@misc{pith2026190809770,
  author       = {Pith},
  title        = {Pith review of: FACT -- Multi-wavelength analysis of more than 30 flares of Mrk 421},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/WG3IKNRP}},
  note         = {Machine review of arXiv:1908.09770}
}
read the original abstract

Mrk 421 is a high-synchrotron-peaked blazar featuring bright and persistent GeV and TeV emission. We use multi-wavelength light curves of Mrk 421 spanning 5.5 years with FACT (TeV) and Fermi LAT (GeV) in the gamma rays, Swift BAT, Swift XRT and MAXI in the X-rays, together with optical and radio data and investigate the physical processes driving the emission and variability. Observations by FACT are continuous and not triggered, so the source was found in a wide range of flux states and more than 30 flares were identified from X-rays to TeV. The light curves in TeV and X-rays feature very similar flares with rise and decay times of a few days and zero lag, characteristic for electron processes. At least two parameters per flare, the amplitude and the cut-off energy, are required to explain the observed variability. In addition, the GeV light curve leads and is strongly correlated with the optical and radio light curves as expected from SSC emitting shock propagating in a conical jet.

Figures

Figures reproduced from arXiv: 1908.09770 by the authors.

Figure 1
Figure 1. DCF cross-correlations of TeV (FACT) and X-rays (M [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. GeV to radio response profile. The y axis is in arbitrary units. 4 [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Synthetic radio light curve (top) derived from Fer [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗

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Works this paper leans on

28 extracted references · 11 canonical work pages

  1. [25]

    Türler, T

    M. Türler, T. J.-L. Courvoisier and S. Paltani, Modelling the submillimetre-to-radio flaring behaviour of 3C 273 , A&A 349 (1999) 45 [ astro-ph/9906274]

    arXiv 1999

  2. [1]

    A. A. Abdo, M. Ackermann, M. Ajello, L. Baldini, J. Ballet , G. Barbiellini et al., Fermi Large Area Telescope Observations of Markarian 421: The Mis sing Piece of its Spectral Energy Distribution, ApJ 736 (2011) 131 [1106.1348]

    arXiv 2011

  3. [2]

    Cerruti, A

    M. Cerruti, A. Zech, C. Boisson and S. Inoue, A hadronic origin for ultra-high-frequency-peaked BL Lac objects, MNRAS 448 (2015) 910 [1411.5968]

    arXiv 2015

  4. [3]

    Mücke and R

    A. Mücke and R. J. Protheroe, A proton synchrotron blazar model for flaring in Markarian 501, Astroparticle Physics 15 (2001) 121 [ astro-ph/0004052]

    arXiv 2001

  5. [4]

    Aleksi ´c, L

    J. Aleksi ´c, L. A. Antonelli, P . Antoranz, A. Babic, U. Barres de Almeid a, J. A. Barrio et al., Rapid and multiband variability of the TeV bright active nuc leus of the galaxy IC 310 , A&A 563 (2014) A91 [ 1305.5147]

    arXiv 2014

  6. [5]

    Evolution of the Synchrotron Spectrum in Mrk421 during the 1998 Campaign

    C. Tanihata, J. Kataoka, T. Takahashi and G. M. Madejski, Evolution of the Synchrotron Spectrum in Markarian 421 during the 1998 Campaign , ApJ 601 (2004) 759 [astro-ph/0310592]

    work page Pith review arXiv 2004

  7. [6]

    Aleksi ´c, S

    J. Aleksi ´c, S. Ansoldi, L. A. Antonelli, P . Antoranz, A. Babic, P . Bangale et al., The 2009 multiwavelength campaign on Mrk 421: V ariability and correlation studies, A&A 576 (2015) A126 [1502.02650]

    arXiv 2015

  8. [7]

    FACT - Long-term Monitoring of Bright TeV-Blazars

    D. Dorner, A. Biland, T. Bretz, J. Buss, S. Einecke, D. Eis enacher et al., F ACT - Long-term Monitoring of Bright TeV-Blazars, arXiv e-prints (2013) [ 1311.0478]

    work page Pith review arXiv 2013

Show all 28 references
  1. [8]

    Anderhub, M

    H. Anderhub, M. Backes, A. Biland, V . Boccone, I. Braun, T . Bretz et al., Design and operation of F ACT - the first G-APD Cherenkov telescope , Journal of Instrumentation 8 (2013) P06008 [ 1304.1710]

    2013 arXiv

  2. [9]

    Hildebrand, M

    D. Hildebrand, M. L. Ahnen, M. Balbo, A. Biland, T. Bretz, J. Buss et al., Using Charged Cosmic Ray Particles to Monitor the Data Quality of F ACT, 35th International Cosmic Ray Conference, Proceedings of Science 301 (2017) 779

    2017

  3. [10]

    Mahlke, T

    M. Mahlke, T. Bretz, J. Adam, L. M. Ahnen, D. Baack, M. Bal bo et al., F ACT - Searching for periodicity in five-year light-curves of Active Galacti c Nuclei, 35th International Cosmic Ray Conference, Proceedings of Science 301 (2017) 612. 6 Multi-wavelength analysis of more th...

    2017

  4. [11]

    Bretz, Zenith angle dependence of the cosmic ray rate as measured wi th imaging air-Cherenkov telescopes, Astroparticle Physics 111 (2019) 72 [ 1902.03875]

    T. Bretz, Zenith angle dependence of the cosmic ray rate as measured wi th imaging air-Cherenkov telescopes, Astroparticle Physics 111 (2019) 72 [ 1902.03875]

    2019 arXiv

  5. [12]

    Riegel, T

    B. Riegel, T. Bretz, D. Dorner, K. Berger and D. Höhne, A systematic study of the interdependence of IACT image parameters, 29th International Cosmic Ray Conference 5 (2005) 215

    2005

  6. [13]

    W. B. Atwood, A. A. Abdo, M. Ackermann, W. Althouse, B. An derson, M. Axelsson et al., The Large Area Telescope on the Fermi Gamma-Ray Space Telescope Mission, ApJ 697 (2009) 1071 [ 0902.1089]

    2009 arXiv

  7. [14]

    W. H. Baumgartner, J. Tueller, C. B. Markwardt, G. K. Ski nner, S. Barthelmy, R. F. Mushotzky et al., The 70 Month Swift-BAT All-sky Hard X-Ray Survey , ApJS 207 (2013) 19 [1212.3336]

    2013 arXiv

  8. [15]

    D. N. Burrows, J. E. Hill, J. A. Nousek, J. A. Kennea, A. We lls, J. P . Osborne et al., The Swift X-Ray Telescope, Space~Sci.~Rev. 120 (2005) 165 [astro-ph/0508071]

    2005 arXiv

  9. [16]

    Matsuoka, K

    M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Suzuki et al., The MAXI Mission on the ISS: Science and Instruments for Monitoring A ll-Sky X-Ray Images, PASJ 61 (2009) 999 [0906.0631]

    2009 arXiv

  10. [17]

    P . W. A. Roming, T. E. Kennedy, K. O. Mason, J. A. Nousek, L . Ahr, R. E. Bingham et al., The Swift Ultra-Violet/Optical Telescope, Space~Sci.~Rev. 120 (2005) 95 [astro-ph/0507413]

    2005 arXiv

  11. [18]

    P . S. Smith, E. Montiel, S. Rightley, J. Turner, G. D. Sch midt and B. T. Jannuzi, Coordinated Fermi/Optical Monitoring of Blazars and the Great 2009 September G amma-ray Flare of 3C 454.3, arXiv e-prints (2009) [ 0912.3621]

    2009 arXiv

  12. [19]

    V aughan, R

    S. V aughan, R. Edelson, R. S. Warwick and P . Uttley, On characterizing the variability properties of X-ray light curves from active galaxies , MNRAS 345 (2003) 1271 [astro-ph/0307420]

    2003 arXiv

  13. [20]

    Poutanen, A

    J. Poutanen, A. A. Zdziarski and A. Ibragimov, Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulatio n and spectral hardness on the superorbital phase, MNRAS 389 (2008) 1427 [ 0802.1391]

    2008 arXiv

  14. [21]

    Aleksi ´c, S

    J. Aleksi ´c, S. Ansoldi, L. A. Antonelli, P . Antoranz, A. Babic, P . Bangale et al., Unprecedented study of the broadband emission of Mrk 421 dur ing flaring activity in March 2010, A&A 578 (2015) A22 [1412.3576]

    2015 arXiv

  15. [22]

    B. M. Peterson, I. Wanders, K. Horne, S. Collier, T. Alex ander, S. Kaspi et al., On Uncertainties in Cross-Correlation Lags and the Reality of Wavelength-dependent Continuum Lags in Active Galactic Nuclei , PASP 110 (1998) 660 [astro-ph/9802103]

    1998 arXiv

  16. [23]

    M. L. Ahnen, S. Ansoldi, L. A. Antonelli, P . Antoranz, A. Babic, B. Banerjee et al., Long-term multi-wavelength variability and correlation s tudy of Markarian 421 from 2007 to 2009, A&A 593 (2016) A91 [ 1605.09017]. 7 Multi-wavelength analysis of more than 30 flares of Mrk 42...

    2016

  17. [24]

    J. D. Scargle, J. P . Norris, B. Jackson and J. Chiang, Studies in Astronomical Time Series Analysis. VI. Bayesian Block Representations, ApJ 764 (2013) 167 [1207.5578]

    2013 arXiv

  18. [26]

    Esposito, R

    V . Esposito, R. Walter, P . Jean, A. Tramacere, M. Türler, A. Lähteenmäki et al., The high energy spectrum of 3C 273 , A&A 576 (2015) A122 [1503.02980]

    2015 arXiv

  19. [27]

    J. L. Richards, W. Max-Moerbeck, V . Pavlidou, O. G. King , T. J. Pearson, A. C. S. Readhead et al., Blazars in the Fermi Era: The OVRO 40 m Telescope Monitoring P rogram, ApJS 194 (2011) 29 [ 1011.3111]

    2011 arXiv

  20. [28]

    Gehrels and Swift Team, The Swift γ-ray burst mission, New Astronomy Reviews 48 (2004) 431

    N. Gehrels and Swift Team, The Swift γ-ray burst mission, New Astronomy Reviews 48 (2004) 431. 8

    2004

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