Systematic investigation of X-ray spectral variability of TeV blazars during flares in the $RXTE$ era

Abstract

Utilizing all the 16-year $RXTE$ observations, we analyze the X-ray spectra of 32 TeV blazars, and perform a systematic investigation of X-ray spectral variability for the 5 brightest sources during their major flares that lasted several days. We obtain photon spectral index ($\alpha$), flux and synchrotron radiation peak energy ($E_{\mathrm{p}}$) from empirical spectral fitting, and electron spectral index ($p$) from theoretical synchrotron radiation modeling. We find that both $\alpha$ and $p$ generally display a harder-when-brighter trend, confirming the results of many previous works. Furthermore, we confirm and strengthen the result that $p$ must vary in order to explain the observed X-ray spectral variability during flares, which would have useful implications for interpreting the associated higher-energy spectral variability. We see apparent electron spectral hysteresis in many but not all $p$-flux plots that takes a form of "loop" or oblique"8". We obtain a tight $p$-hardness ratio (HR) relation and a tighter $p$-$\alpha$ relation using spectra of flaring periods, both of which are also applicable to stacked data of quiescent periods. We demonstrate that these two empirical relations can be used efficiently to estimate $p$ from HR or $\alpha$ that is readily achieved. Finally, we find that, when considering TeV blazars as a whole, $\alpha$ and X-ray luminosity are positively correlated, $E_{\mathrm{p}}$ is negatively correlated with $p$ and $\alpha$, and $E_{\mathrm{p}}$ is positively correlated with HR; all these correlations are in line with the blazar sequence. However, after correcting for the Doppler boosting effect, $\alpha$ and intrinsic X-ray luminosity follow an anti-correlation.

arXiv comment23 pages, 11 figures, 2 tables. Accepted for publication in ApJ

References in corpus (64)

• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• Unified Schemes for Radio-Loud Active Galactic Nuclei
• A Unifying View of the Spectral Energy Distributions of Blazars
• The Spectral Energy Distribution of Fermi bright blazars
• A theoretical unifying scheme for gamma-ray bright blazars
• Leptonic and Hadronic Modeling of Fermi-Detected Blazars
• The Connection between X-ray- and Radio-Selected BL Lacertae Objects
• BL Lac Objects in the Synchrotron Proton Blazar Model
• Fast TeV variability in blazars: jets in a jet
• TeV Gamma Rays from BL Lac Objects due to Synchrotron Radiation of Extremely High Energy Protons
• A Proton Synchrotron Blazar Model for Flaring in Markarian~501
• Internal shocks in the jets of radio-loud quasars
• 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
• BeppoSAX Observations of Unprecedented Synchrotron Activity in the BL Lac Object Mkn 501
• 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
• Neutral Beams from Blazar Jets
• A High Resolution X-ray Image of the Jet in M 87
• Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated Variability
• Spectral Properties of Bright Fermi-detected Blazars in the Gamma-ray Band
• The Spectral Energy Distributions of Fermi Blazars
• X-Ray Spectral Variability Signatures of Flares in BL Lac Objects
• TeV and Multi-wavelength Observations of Mrk 421 in 2006-2008
• The Outburst of HST-1 in the M87 Jet
• Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
• X-ray spectral evolution of TeV BL Lac objects: eleven years of observations with BeppoSAX, XMM-Newton and SWIFT satellites
• The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
• Variability Pattern and the Spectral Evolution of the BL Lacertae Object PKS 2155-304
• X-ray Emission of Mkn 421: New Clues From Its Spectral Evolution. II. Spectral Analysis and Physical Constraints
• Signatures of synchrotron emission and of electron acceleration in the X-ray spectra of Mrk 421
• Four Years Monitoring of Blazar PKS 2155-304 with BeppoSAX: Probing the Dynamics of the Jet
• Flaring X-ray Emission from HST-1, a Knot in the M87 Jet
• Blazar sequence - an artefact of Doppler boosting
• X-ray Flaring Activity of Mrk 421
• Intrinsic Curvature in the X-ray Spectra of BL Lacertae Objects
• Optical Polarization and Spectral Variability in the M87 Jet
• Observing Mkn 421 with XMM--Newton: the EPIC--PN point of view
• Simultaneous Multiwavelength Observations of Markarian 421 During Outburst
• Simultaneous Multiwavelength observation of Mkn 501 in a low state in 2006
• Long-Term X-Ray and TeV variability of Mrk 501
• Full Spectral Survey of Active Galactic Nuclei in the Rossi X-ray Timing Explorer Archive
• XMM-Newton timing mode observations of Mrk 421
• XMM-Newton view of PKS 2155-304: hardness ratio and cross-correlation analysis of EPIC pn observations
• Evolution of the Synchrotron Spectrum in Mrk421 during the 1998 Campaign
• Intrinsic Correlations for Flaring Blazars Detected by Fermi
• Role of Reconnection in AGN Jets
• X-ray Flares from Markarian 501
• Spectral Survey of X-Ray Bright Active Galactic Nuclei from the Rossi X-ray Timing Explorer
• A search for spectral hysteresis and energy-dependent time lags from X-ray and TeV gamma-ray observations of Mrk 421
• The debeamed luminosity, sychrotron peak frequency and black hole mass of BL Lac objects
• Observation of X-ray variability in the BL Lac object 1ES1959+65
• Modeling the Multiwavelength Spectra and Variability of BL Lacertae in 2000
• Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton
• X-Ray Spectral Variability of PKS 2005-489 During the Spectacular November 1998 Flare
• Multiwavelength Observations of the BL Lacertae Object PKS 2155-304 with XMM-Newton
• An active state of the BL Lac Object Markarian 421 detected by INTEGRAL in April 2013
• Flux and spectral variability of the blazar PKS 2155-304 with XMM-Newton: Evidence of Particle Acceleration and Synchrotron Cooling
• EGRET Spectral Index and the Low-Energy Peak Position in the Spectral Energy Distribution of EGRET-Detected Blazars
• Extremely rapid x-ray flares of tev blazars in the rxte era
• A Suzaku X-Ray Study of the Particle Acceleration Processes in the Relativistic Jet of Blazar Mrk 421
• TeV $\gamma$-ray fluxes from the long campaigns on Mrk421 as constraints on the emission of TeV-PeV Neutrinos and UHECRs
• X-ray Spectral Variability of TeV Blazars during Rapid Flares
• Lower Bound on the Cosmic TeV Gamma-ray Background Radiation
• Ground-based Gamma Ray Astronomy
• First Results from NuSTAR Observations of Mkn 421

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