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

Teräsranta et al. 2005

- 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

1) Nature of variations JETS. SHOCKS.

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

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

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)

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?

- 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.

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

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

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

Marscher et al., Nature (tomorrow!)

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

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

MOVIE!

Six times 3C 279, June 1991

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 %

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

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

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.

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

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

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.]

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

...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 2007 + others)

dee ja nyypeak

There is no blazar sequence. [Nieppola poster]

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

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)

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

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

Big BH mass  fast jet ?

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

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

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.