XMM-Newton View of TeV Blazars

5th micro-quasar workshop 123/4/22

XMM-Newton View of TeV Blazars

张有宏清华大学天体物理中心

23/4/22 黑洞天体物理前沿问题年度研讨会（ 2006 ） 2

Outline Introduction to Blazars X-ray variability properties of TeV blazars Blazars vs GRBs vs micro-quasars/blazars Multi-wavelength observations of PKS2155-304

with XMM-Newton (our work); comparisons with other coordinated multi-wavelength observations

XMM-Newton timing mode observations of Mrk 421 (other work)

Physical implications inferred from the observations


Blazar SED Sequence Nonthermal emission

• Low energy: Synchrotron• High energy: Inverse Compton

Luminosity-related SED?• Peak energy (synchrotron)• HBLs, LBLs, FSRQs• Cooling-dependent

Variability comparison• Same mechanism• GRBs and micro-

quasars (micro-blazars)

X-rayoptical

(Fossati et al . 1998)


(Mirabel, Sky and Telescope, May 2002, 32)

Jet/Synchrotron Emission


TeV Blazars 6 TeV blazars (confirmed):

• Mrk 421, PKS 2155-304, Mrk 501 HBLs: synchrotron component peaks at UV-X-

rays • X-ray emission are the high energy tail of

synchrotron emission • X-rays are expected to be violently variable • To probe particle acceleration and cooling of

relativistic particles


由李 -马公式的引用看甚高能伽玛射线天文学的兴衰


X-ray Variability of TeV blazars: ASCA/SAX/RXTE Flux variations:

• Timescales: ~ days with rapid flicker superimposed• Variability amplitude: energy dependent• PSD: not useful, slpoe ~ 2.5• Cross-correlation function (CCF) time lags

Spectral evolution:• The higher flux, the harder spectrum• Peak energy shifts to higher energy with higher flux

Mrk 501: ~100 keV by SAX (Pian et al. 1998) Similar optical variability in LBLs (e.g., BL Lac

observed with Tsinghua 80cm telescopes)


X-ray time lags of TeV blazars Time lags are different from flare to flare:

• Soft lags: soft photons lag hard ones • Hard lags: hard photons lag soft ones• Amplitude of lags: 0 - ~3 hours?

Time lags appear to correlate with• Photon energy • Flare’s duration• Spectral slope• Timescale (Fourier frequency) ?


Lags: TeV blazars vs microquasars and GRBs TeV blazars: X-ray soft/hard lags GRBs: gamma-ray soft lags (hard lags?):cooling/accelerating time scales of relativistical electrons

jet/synchrotron mechanism for X-ray (optical-UV) in TeV blazars, and gamma-ray (X-ray-Optical) in GRBs

Microblazars, microquasars, X-ray binaries• Hard lags: Comptonization of soft photons by reletivistic

electrons From hot corona or from the jets Hard (Soft?) lags jet/synchrotron X-ray (lower energy) emission?

• More complicated: e.g. soft X-rays may be dominated by the accretion disk


Multi-wavelength variability of TeV blazars Strongest constraints on emission models

Multi-wavelength variability: • Peak fluxes correlated: Mrk 421• Different correlations over different timescales

Whether X-ray variability properties can be extrapolated to UV-Optical bands?• Coordinated multi-wavelength observations• Optical-UV and X-ray instruments onboard XMM


XMM-Newton observations of TeV blazars

Calibration sources, observed about twice per year (and Guest Observers)

Mrk 421 (31obs. > 9 orbits) and PKS 2155-304 (9 orbits) over about 6 years

Optical-UV-X-ray observations of PKS 2155-304

X-ray timing mode observations of Mrk 421


UV and X-ray observations of PKS 2155-304 Orbit 087: 2000 May 30-31 (Zhang et al. 2006) ~ 0.3 days lag of UV to soft X-rays???


UV and X-ray observations of PKS 2155-304 Orbit 171: 2000 Nov 19-20 (Zhang et al. 2006) ~ no detectable lag of UV to X-ray (if, hard

lag?)


UV and X-ray observations of PKS 2155-304 Variability amplitude vs energy


UV and X-ray observations of PKS 2155-304 Soft X-ray/UV hardness ratio vs count-rate


Optical and X-ray observations of PKS 2155-304

Orbit 362: 2001 November 30


Comparison with previous multi-wavelength observations 1991 November, achromatic quasi-periodic

variability, soft X-rays (25A) led UV (1400A) by ~ 1 hour (Edelson et al. 1995)


Comparison with previous multi-wavelength observations 1994 May: well-defined flare; variability amplitude

decreased, and temporal profile broadened with increasing wavelengths; X-rays led EUV and UV by ~ 1 and 2 days (Urry et al. 1997)


XMM-Newton multi-wavelength observations: intra-day variability

Previous coordinated multi-wavelength observations: inter-day variability

Complex multi-wavelength observations can occur over different timescales

XMM-Newton multi-wavelength observations are superior:• Resolution• Signal-to-noise ratio


XMM timing mode observations of Mrk421 Currently the highest Signal-to-noise ratio (Brinkmann

et al. 2005)


Time-resolved CCF analysis Sliding window (2000s, 6000s, and 20000s)


Characteristic timescales? 5.2 ks, 7.2 ks, 10 ks for orbit 084, 546, 807


Physical implications Correlations at different time lags a common

“synchrotron” origin Substantially different patterns of variability

over different timescales constraints on radiation models would be different from epoch to epoch, requiring, e.g., • changes in the parameters characterizing the emitting

region or • different mechanisms operating


Homogeneous Scenario

the smaller the lag, the larger the combination of B andδ

Zhang et al. (2002)


UV vs X-ray lags ~ 2 days in 1994 May < 800 s in 2000 November

the ratio of B between 2000 November and 1994 May would be> 36 (δ ～ 10)

the extreme values of B to be unacceptable in reality, but


Interpretation of the observed lags may be very likely affected by, e.g., inhomogeneous emitting region(s):• stratified shock model or • an energy dependent volume


Shoch-in-jet model At tobs, emission from certain position R(t), and earlier emission

from all positions; >~ 60% “background emission” Two-colliding-shell model: shock structure developed;

noticeable changes of the physical state of emission region and unexpected changes of emission properties (Brinkmann et al. 2005).


Conclusions The complex variability behaviour of TeV blazars; It appears hard to uniquely constrain the underlying

physical properties for the emission process from the observations;

Better observations and extended relativistic MHD numerical simulations

Well-defined major fares (possibly a single episode) might still provide the most likely situation to probe any detailed insight, e.g., • any connection between the sign of the lags and the rise

and decay of the flux, and • any relation between the lags (sign) and the peak energy

of the synchrotron emission.

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XMM-Newton View of TeV Blazars