A search for spectral hysteresis and energy-dependent time lags from X-ray and TeV gamma-ray observations of Mrk 421

Abstract

Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray bands, where the broadband spectral energy distributions usually peak. In this work, we report on three "target-of-opportunity" (ToO) observations of Mrk 421, one of the brightest TeV blazars, triggered by a strong flaring event at TeV energies in 2014. These observations feature long, continuous, and simultaneous exposures with XMM-Newton (covering X-ray and optical/ultraviolet bands) and VERITAS (covering TeV gamma-ray band), along with contemporaneous observations from other gamma-ray facilities (MAGIC and Fermi-LAT) and a number of radio and optical facilities. Although neither rapid flares nor significant X-ray/TeV correlation are detected, these observations reveal subtle changes in the X-ray spectrum of the source over the course of a few days. We search the simultaneous X-ray and TeV data for spectral hysteresis patterns and time delays, which could provide insight into the emission mechanisms and the source properties (e.g. the radius of the emitting region, the strength of the magnetic field, and related timescales). The observed broadband spectra are consistent with a one-zone synchrotron self-Compton model. We find that the power spectral density distribution at $\gtrsim 4\times 10^{-4}$ Hz from the X-ray data can be described by a power-law model with an index value between 1.2 and 1.8, and do not find evidence for a steepening of the power spectral index (often associated with a characteristic length scale) compared to the previously reported values at lower frequencies.

arXiv comment45 pages, 15 figures

References in corpus (46)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs
• A Unifying View of the Spectral Energy Distributions of Blazars
• On characterising the variability properties of X-ray light curves from active galaxies
• Leptonic and Hadronic Modeling of Fermi-Detected Blazars
• The XMM-Newton Optical/UV Monitor Telescope
• The Connection between X-ray- and Radio-Selected BL Lacertae Objects
• 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
• TeV Gamma Rays from BL Lac Objects due to Synchrotron Radiation of Extremely High Energy Protons
• Constraints on the Physical Parameters of TeV Blazars
• Measuring the broadband power spectra of active galactic nuclei with RXTE
• Background Modelling in Very-High-Energy gamma-ray Astronomy
• Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope
• A Multi-wavelength View of the TeV Blazar Markarian 421: Correlated Variability, Flaring, and Spectral Evolution
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• X-Ray Spectral Variability Signatures of Flares in BL Lac Objects
• TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008
• Host galaxy subtraction of TeV candidate BL Lacertae objects
• Time Dependent Modeling of the Markarian 501 X-ray and TeV Gamma-Ray Data Taken During March and April, 1997
• Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
• Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
• The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
• Characteristic X-ray Variability of TeV Blazars: Probing the Link between the Jet and the Central Engine
• Variability Pattern and the Spectral Evolution of the BL Lacertae Object PKS 2155-304
• Limits on an Energy Dependence of the Speed of Light from a Flare of the Active Galaxy PKS 2155-304
• 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
• Discovery of Spectral Variability of Markarian 421 at TeV Energies
• Rapid TeV Gamma-Ray Flaring of BL Lacertae
• X-ray Flaring Activity of Mrk 421
• Correlation between the TeV and X-ray emission in high--energy peaked BL Lac objects
• Temporal and Spectral Variabilities of High Energy Emission from Blazars Using Synchrotron Self-Compton Models
• Mrk 421 as a case study for TeV and X-ray variability in leptohadronic models
• Observation of Markarian 421 in TeV gamma rays over a 14-year time span
• On Compton Scattering Scenarios for Blazar Flares
• Does the Blazar Gamma-Ray Spectrum Harden with Increasing Flux? Analysis of 9 Years of EGRET Data
• Connection between inner jet kinematics and broadband flux variability in the BL Lac object S5 0716+714
• MAXI investigation into the longterm X-ray variability from the very-high-energy gamma-ray blazar Mrk 421
• Statistical evaluation of the flux cross-calibration of the XMM-Newton EPIC cameras
• Self-consistent neutrino and UHE cosmic ray spectra from Mrk 421
• X-Ray Spectral Variability of Extreme BL Lac AGN H1426+428
• Hadronic-Origin orphan TeV flare from the 1ES 1959+650
• Testing Rate Dependent corrections on timing mode EPIC-pn spectra of the accreting Neutron Star GX 13+1
• A Search for Fast X-ray Variability from Active Galactic Nuclei using Swift

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• Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets
• Multiwavelength Variability Signatures of Relativistic Shocks in Blazar Jets
• The Great Markarian 421 Flare of February 2010: Multiwavelength variability and correlation studies
• Multiwavelength observations of the blazar BL Lacertae: a new fast TeV gamma-ray flare
• X-ray flux variability of active galactic nuclei observed using NuSTAR
• Possible Accretion Disk Origin of the Emission Variability of a Blazar Jet
• Swift observations of Mrk\,421 in selected epochs. iii. Extreme x-ray timing/spectral properties and multiwavelength lognormality in 2015\,December--2018\,April
• Systematic investigation of X-ray spectral variability of TeV blazars during flares in the $RXTE$ era
• The HAWC real-time flare monitor for rapid detection of transient events
• Probing an X-ray flare pattern in Mrk 421 induced by multiple stationary shocks: a solution to the bulk Lorentz factor crisis
• Long-term multi-wavelength study of 1ES 0647+250
• Extreme HBL-like behavior of Markarian 421 and its two-zone photohadronic interpretation
• A time-dependent particle acceleration and emission model: Understanding the particle spectral evolution and blazar flares
• Galactic and Extragalactic Sources of Very High Energy Gamma-rays
• Rapid X-ray Variability in Mkn 421 during a Multiwavelength Campaign
• Optical flux and spectral variability of BL Lacertae during its historical high outburst in 2020
• The origin of multi-TeV flares from the nearest blazar Markarian 421
• An Explanation for 13 consecutive days activities of Mrk 421
• Time-Dependent Modeling of the Sub-Hour Spectral Evolution During the 2013 Outburst of Mrk 421
• Separating source-intrinsic and Lorentz invariance violation induced delays in the very high energy emission of blazar flares
• Properties and Possible Physical Origins of $\gamma$-ray Emission in Extreme Synchrotron Blazars
• Future Detections of the Warm-Hot Intergalactic Medium using Bright Power Law Sources with NewAthena
• X-ray Fourier lag-frequency spectra modulated by stochastic turbulent acceleration in the jets of high-frequency-peaked BL Lac