1. Total intensity radio variations in blazars
Esko Valtaoja
Tuorla Observatory, University of Turku, Finland
Metsähovi Radio Observatory, Helsinki University of Technology
TUORLA-METSÄHOVI AGN GROUP: Talvikki Hovatta, Elina
Lindfors, Anne Lähteenmäki, Elina Nieppola, Pia-Maria
Saloranta, Ilona Torniainen, Merja Tornikoski, Kaj Wiik

3. Teräsranta et al. 2005

4. - what causes the radio flux and variability?
Nature of variations
- what causes the radio flux and variability?
2) Multifrequency comparisons
- the advantage of a movie over a snapshot
3) Fundamental physics of AGN
- understanding the basics

5. 1) Nature of variations
JETS.
SHOCKS.

6. Marscher & Gear shock-in-jet model (1985)
(picture
courtesy of
Marc Türler)

7. Valtaoja et al. 1992
Valtaoja et al. 1988
Stevens et al. 1995

8. Ten years of 3C 279 cm-to-optical variations modelled as
”M & G” shocks in a jet (Lindfors et al., 2006, original
code developed by Marc Türler)

9. Exponential rise, sharp peak, exponential decay
(Valtaoja et al. 1999)
Theory and simulations: quite different flare shapes
(Gomez et al. 1997) ... are we missing something crucial?

10. - does one mechanism (shocks) explain all major variations?
what about flickering, intraday variability (too high Tb!)
primary causes & parameters: timescales, luminosities, frequency
of shocks, specificity of individual shocks (high/low-peaking), etc.

11. inverse correlation
between  and time
interval between flares?
(flare frequency related
to jet opening angle??)
[Hovatta et al. 2007]
sources with most luminous
shocks are also the most
active? (no”memory” in
shock production?)
remarkably narrow range in
flare timescales (occurrence,
duration) over 5 mags of
luminosity

12. KNOW where radio variations come from: spatial and temporal anchor
© Alan Marscher

13. 2) Multifrequency comparisons: movies!
OJ 287, 12-year periodic flaring

14. Marscher et al., Nature (tomorrow!)

15. Origin of gamma-rays? external photon synchrotron photon
dominated (EC)
”where the photons are”
synchrotron photon
dominated (SSC)
”where the electrons are”

16. Six times 3C 279,
June 1991
theoretical synchrotron spectra with little (no)
connection to reality
one-zone model spectra, in disagreement with the
basic shocked jet framework
- snapshots with no temporal framework or constraints

17. MOVIE!

18. Six times 3C 279,
June 1991

19. EGRET vs continuum sample: radio flare starts before gamma flare
3C 279: the more
distant the shock, the
weaker the gamma
flare [Lindfors et al. 2006]
P = 99,98%
EGRET vs continuum sample: radio
flare starts before gamma flare
[Valtaoja & Teräsranta 1995; Lähteenmäki
& Valtaoja 2003]
P = 99,9 %

20. - - - parsec(s) - - -
- - - parsec(s) - - -
2) gamma-ray flare
(EC photons)
radio flare / new shock
emerges

21. - - - parsec(s) - - -
- - - parsec(s) - - -
radio flare / new shock
emerges from radio core
2) shock grows, gamma
peaks (SSC photons)

22. External Compton fails.
All continuum + VLBI data vs EGRET:
strong gamma radiation comes from shocks
on the average 2 months old (observer’s
frame) = several parsecs down the jet
[Jorstad et al. 2001; Lähteenmäki & Valtaoja 2003]
radio and
gamma come
from here!
EC photons
are here
External Compton fails.

23. 3C 279, June 1991:Synchrotron-self-Compton also fails.
(Lindfors, Valtaoja & Türler, A&A 2005)

24. 3) Fundamental physics of AGN jet speed BH mass accretion rate BH spin
jet luminosity
viewing angle
3) Fundamental
physics of AGN

25. variability timescale  brightness temperature Tb(obs) 
Doppler boosting factor
Dvar = [Tb(obs)/Tb(lim)]1/3
apparent expansion speed app+ D
 Lorentz factor 
+ viewing angle 
[Lähteenmäki & Valtaoja 1999; Hovatta et al. in prep.]

26. Blazar sequence? (Ghisellini et al. 1998) One-parameter
Most powerful sources
have lowest synchrotron
peak frequencies
One-parameter
(total power) family:

27. ...but fuller samples destroy the sequence!
Nieppola et al. 2006:
381 Northern Veron-
Cetty&Veron BL Lacs,
a ”complete” sample
(also Giommi et al. 2005; Padovani others)

28. dee ja nyypeak

29. There is no blazar sequence. [Nieppola poster]

30. BL Lacs: D-corrected
[Nieppola poster]
TeV sources:
most luminous
rarest
least Doppler-boosted
(smallest Lorentz
factors?)

31. There’s something wrong with...
... common assumptions about the
gamma-ray generation mechanism
(no external accretion disk / cloud photons)
... common assumptions about the
basic physical parameters of blazars
(no blazar sequence)
... common assumptions about the
nature of TeV sources
(true properties opposite to those assumed
by theoreticians)

32. Classification, unification...
Classification, unification...
Lähteenmäki & Valta-
oja 1999; Hovatta et al.,
in preparation

33. BH MASS as the fundamental parameter?
(work in progress, Tuorla & Metsähovi & UNAM):
from spectroscopy
and imaging
BH MASS
2 more
observables:
L(peak, IC)
n(peak, IC)
2 main observables:
L(peak) DOPPLER-
n(peak) CORRECTED!
2 main jet parameters:
G (jet speed)
q (viewing angle)
from continuum and VLBI
monitoring: D + bapp G + 
(Lähteenmäki and Valtaoja 1999)
from SEDs

34. Big BH mass  fast jet ?

35. SED peak frequency depends also on other
parameters than just black hole mass ?

36. Fast jets have low SED peak frequencies
quasars / BL Lacs
Fast jets have low SED peak frequencies

37. Radio monitoring provides movies (with not too many
frames missing) instead of snapshots: temporal anchor
Only in radio we are pretty sure where the flux
and the variability comes from: spatial anchor
Especially when combined with other multifrequency and
multiapproach data, radio monitoring is a very powerful
tool for testing various theoretical models, AGN classification
and unification, and a key for deriving the fundamental
properties of jets.