Multi-year characterisation of the broad-band emission from the intermittent extreme BL Lac 1ES~2344+514

Abstract

The BL Lac 1ES 2344+514 is known for temporary extreme properties (e.g., a shift of the synchrotron SED peak energy ${\nu }_{synch,p}$ above 1keV). While those extreme states were so far observed only during high flux levels, additional multi-year observing campaigns are required to achieve a coherent picture. Here, we report the longest investigation of the source from radio to VHE performed so far, focusing on a systematic characterisation of the intermittent extreme states. While our results confirm that 1ES 2344+514 typically exhibits ${\nu }_{synch,p}>$1keV during elevated flux periods, we also find periods where the extreme state coincides with low flux activity. A strong spectral variability thus happens in the quiescent state, and is likely caused by an increase of the electron acceleration efficiency without a change in the electron injection luminosity. We also report a strong X-ray flare (among the brightest for 1ES 2344+514) without a significant shift of ${\nu }_{synch,p}$. During this particular flare, the X-ray spectrum is among the softest of the campaign. It unveils complexity in the spectral evolution, where the common harder-when-brighter trend observed in BL Lacs is violated. During a low and hard X-ray state, we find an excess of the UV flux with respect to an extrapolation of the X-ray spectrum to lower energies. This UV excess implies that at least two regions contribute significantly to the infrared/optical/ultraviolet/X-ray emission. Using the simultaneous MAGIC, XMM-Newton, NuSTAR, and AstroSat observations, we argue that a region possibly associated with the 10 GHz radio core may explain such an excess. Finally, we investigate a VHE flare, showing an absence of simultaneous variability in the 0.3-2keV band. Using a time-dependent leptonic modelling, we show that this behaviour, in contradiction to single-zone scenarios, can instead be explained by a two-component model.

arXiv commentAccepted for publication in Astronomy & Astrophysics

References in corpus (64)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• Correcting for the Effects of Interstellar Extinction
• The Swift X-ray Telescope
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• The Swift Ultra-Violet/Optical Telescope
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Fermi Large Area Telescope Fourth Source Catalog
• On characterising the variability properties of X-ray light curves from active galaxies
• The Pan-STARRS1 Photometric System
• Spectral Energy Distributions of Hard X-ray selected AGNs in the XMDS Survey
• On Uncertainties in Cross-Correlation Lags and the Reality of Wavelength-Dependent Continuum Lags in Active Galactic Nuclei
• Blazars in the Fermi Era: The OVRO 40-m Telescope Monitoring Program
• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• The Fermi Large Area Telescope On Orbit: Event Classification, Instrument Response Functions, and Calibration
• Constraints on the Physical Parameters of TeV Blazars
• Doppler factors, Lorentz factors and viewing angles for quasars, BL Lacertae objects and radio galaxies
• A Proton Synchrotron Blazar Model for Flaring in Markarian~501
• Multiwavelength Observations of Strong Flares From the TeV-Blazar 1ES 1959+650
• Log-parabolic spectra and particle acceleration in the BL Lac object Mkn 421: spectral analysis of the complete BeppoSAX wide band X-ray data set
• The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• Gamma-ray Light Curves and Variability of Bright Fermi-Detected Blazars
• Particle acceleration at ultrarelativistic shocks: an eigenfunction method
• Generating artificial light curves: Revisited and updated
• Swift observations of the very intense flaring activity of Mrk 421 during 2006: I. Phenomenological picture of electron acceleration and predictions for the MeV/GeV emission
• A hadronic origin for ultra-high-frequency-peaked BL Lac objects
• Extreme synchrotron BL Lac objects
• TeV BL Lac objects at the dawn of the Fermi era
• Log-parabolic spectra and particle acceleration in blazars. III: SSC emission in the TeV band from Mkn 501
• Blazar spectral variability as explained by a twisting inhomogeneous jet
• Discovery of >350 GeV Gamma Rays from the BL Lacertae Object 1ES 2344+514
• Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars
• Relativistic Jets in Active Galactic Nuclei und Microquasars
• Time-correlation between the radio and gamma-ray activity in blazars and the production site of the gamma-ray emission
• A method for the estimation of the significance of cross-correlations in unevenly sampled red-noise time series
• The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
• Radio/gamma-ray time delay in the parsec-scale cores of active galactic nuclei
• Log-parabolic spectra and particle acceleration in blazars - II: The BeppoSAX wide band X-ray spectra of Mkn 501
• Fermi Large Area Telescope Fourth Source Catalog Data Release 2
• MOJAVE: XVIII. Kinematics and Inner Jet Evolution of Bright Radio-Loud Active Galaxies
• The NuSTAR view on Hard-TeV BL Lacs
• Superorbital variability of X-ray and radio emission of Cyg X-1 - II. Dependence of the orbital modulation and spectral hardness on the superorbital phase
• Performance of the MAGIC telescopes under moonlight
• The extreme HBL behaviour of Markarian 501 during 2012
• Correlation between the TeV and X-ray emission in high--energy peaked BL Lac objects
• The radio delay of the exceptional 3C 454.3 outburst. Follow-up WEBT observations in 2005-2006
• The GASP-WEBT monitoring of 3C 454.3 during the 2008 optical-to-radio and gamma-ray outburst
• Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets
• Observation of very high energy gamma-rays from the AGN 1ES 2344+514 in a low emission state with the MAGIC telescope
• Detection of Exceptional X-Ray Spectral Variability in the TeV BL Lac 1ES 2344+514
• Multiwavelength Cross-Correlations and Flaring Activity in Bright Blazars
• A new hard X-ray selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties
• Synchrotron-Loss Spectral Breaks in Pulsar-Wind Nebulae and Extragalactic Jets
• A combined radio and GeV gamma-ray view of the 2012 and 2013 flares of Mrk 421
• Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017
• Electron-proton co-acceleration on relativistic shocks in extreme-TeV blazars
• The Simultaneous Low State Spectral Energy Distribution of 1ES 2344+514 from Radio to Very High Energies
• X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view
• Infrared properties of blazars: putting the GASP-WEBT sources into context
• An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state
• Radio$-\gamma -$ray response in blazars as a signature of adiabatic blob expansion
• Very-High-Energy $\gamma$-Ray Observations of the Blazar 1ES 2344+514 with VERITAS

Cited by in corpus (5)

• Insights into the broad-band emission of the TeV blazar Mrk 501 during the first X-ray polarization measurements
• X-Ray Spectral Variability of Thirteen TeV High Energy Peaked Blazars with XMM-Newton
• Properties and Possible Physical Origins of $\gamma$-ray Emission in Extreme Synchrotron Blazars
• Broadband Spectral Analysis of 1ES2344+514: A Multi-epoch study
• Extreme Blazars Observed with MAGIC: Second Catalog Release