1. Long-term X-ray Variability in Blazars & its Multiwaveband Context Alan Marscher Boston University Research Web Page: www.bu.edu/blazars Alan Marscher Boston University Research Web Page: www.bu.edu/blazars Free Downloads! - Monthly 43 GHz VLBA images of 29 blazars - Original songs (MP3 format) on science topics

2. Main Collaborators: Major International Effort Svetlana Jorstad, Ritaban Chatterjee, Frannie D’Arcangelo (Boston U.) Vladimir A. Hagen-Thorn & Valeri Larionov (St. Petersburg State U., Russia) Margo & Hugh Aller (University of Michigan) Ian McHardy (U. Southampton, UK) José Luis Gómez & Iván Agudo (IAA, Granada, Spain) Anne Lähteenmäki & Merja Tornikoski (Metsähovi Radio Observatory) Walter Gear (Cardiff U., UK) Esko Valtaoja (Turku U., Finland) Thomas Balonek (Colgate U.) Gino Tosti (U. of Perugia Observatory, Italy) Omar Kurtanidze (Abastumani Observatory, Rep. of Georgia) Martin Gaskell (U. of Texas) H. R. Miller, Kevin Marshall, Wesley Ryle (Georgia St. U.) Matthew Lister (Purdue U.) Thomas Krichbaum, Lars Fuhrmann, Tuomas Savolainen, Yuri Kovalev (MPIfR) Funded by NASA & NSF

3. Main Instruments - A Truly Multiwaveband Effort Lowell Obs. Perkins Telescope: Prism (optical) & Mimir (H-band) (polarimetry) Calar Alto 2.2 m telescope (optical polarimetry) Liverpool Telescope (optical & near-IR light curves & polarimetry) Very Long Baseline Array (7 mm) & Global mm VLBI Array (3 mm) Crimean Astrophysical Observatory 70 cm telescope (polarimetry) St. Petersburg State University 0.4 m telescope (polarimetry) Rossi X-ray Timing Explorer, XMM-Newton, & Swift (X-ray light curves) Chandra, HST, Spitzer (imaging of kpc-scale jets) GLAST (gamma-ray light curves) IRAM 30 m (3 mm polarimetry) University of Michigan Radio Observatory (radio light curves & polarimetry) Metsähovi Radio Observatory (radio light curves) Numerous other optical telescopes & collaborators

4. Relativistic Jets on Parsec & Kiloparsec Scales 3C 111 Scale: 1 mas = 0.92 pc = 3.0 lt-yr (Ho=70) Approximate location of black hole mas

5. Goal: Probe Blazar Jets as far Upstream as Possible We want to probe the section of the jet from the mm-wave core down to the central engine - where we think the jet is accelerated & collimated We also want to study shocks & other disturbances, particle acceleration, changes in flow Lorentz factor, magnetic field geometry, turbulence, interaction with surrounding medium, bending/precession Unbeamed Beamed

6. The Quasar PKS 1510-089 (z=0.361) X-ray/Radio/Optical Light Curves Arrows: Times of superluminal ejections at 43 GHz Major outbursts usually seen at all wavebands, coincident with ejection of superluminal radio knot Which wavebands lead and lag is time dependent Need robust method for determining correlations & their uncertainties & connections with events seen in VLBI images of jet

7. Method for Probing Jet Upstream of Core: Identify Jet Features Responsible for High-frequency Variations Look for correlated polarization variability in optical, IR, submm, & mm-wave  Locate sites of variable high-frequency emission on mm- wave VLBA images  relate optical/near-IR light curves to images Connect radio-optical emission to X-ray &  -ray radiation by correlating light curves (RXTE, Swift, GLAST) with optical/near-IR, & mm-wave light curves  Dynamic multiwaveband emission maps

8. The Quasar 3C 279 (Chatterjee et al. 2008) Extreme variations in flux at optical & X-ray (& γ-ray) Variations in X-ray flux appear well-correlated with changes in optical brightness Cross-correlation analysis of 11 years of X-ray, optical, & radio (15 GHz) monitoring (Uttley et al.) 1.Compute raw PSD 2.Create many simulated light curves with random variations following raw PSD with sampling same as observed 3.Determine “true” PSD + error on slope  red noise spectrum 4.Use true PSD to create many simulated light curves with sampling same as observed 5.Use discrete cross-correlation method to determine correlation of light curves at different 6.Use simulations to determine probability that correlations could be obtained by chance

9. The Quasar 3C 279 (cont.) Variations in X-ray flux well-correlated with changes in optical brightness → time lag of 15±6 days, with optical leading Discrete Cross-Correlation Coefficient (optical vs. X-ray) Positive delay: optical leads Optical/X-ray correlation varies on timescale of few yr - X-ray leads by up to 20 days (1995-1997) - Optical leads by up to 20 days (1999-2002) - ~ zero lag (1997-1999, 2002- 2004) - Weak, broad correlation (2003- 2007)

10. The Quasar 3C 279 (cont.) Variations in X-ray flux well-correlated with changes in jet direction → time lag of 80±150 days, with X-ray flux lagging  Direction of jet determines mean strength of next flare Discrete cross-correlation coefficient (X-ray vs. PA of inner jet, 0.2±0.1 mas from core)

11. The Quasar 3C 279 (Chatterjee et al. 2008) Cross-correlation Analysis  highly significant correlations between light curves: X-ray - optical (time lag varies between +20 and -20 days) X-ray - radio core and X-ray peaks - superluminal ejections (X-ray leads by 114±21 days)  Profiles of optical flares narrower than X-ray (higher E electrons make optical)  Optical-leading flares: shocks or SSC light-travel delays  X-ray-leading flares: gradual acceleration of electrons X/opt radiative E output ratio: ~1 when delay ~ 0 (upstream) Low when delay longer (downstream) »» X-ray & optical emission occurs in ≥ 2 sites upstream of 43 GHz core

12. BL Lac Reveals its Inner Jet (Marscher et al. 2008, Nature, 24/04/08) Late 2005: Double optical/X-ray flare, detection at TeV energies, rotation of optical polarization vector during first flare, radio outburst starts during 2nd flare Superluminal knot coincident with core Strong TeV detection X-ray Optical EVPA matches that of knot during 2nd flare P decreases during rotation  B is nearly circularly symmetric Scale: 1 mas = 1.2 pc TeV data: Albert et al. 2007 ApJL

13. BL Lac: Physical Picture Moving shock follows spiral streamline (does not cover entire jet cross-section) Passes through helical field pattern in acceleration + collimation zone of jet Becomes bright shortly before it emerges into zone of turbulent plasma Physical Picture of BL Lac: Exactly as Expected Theoretically* (It’s a Miracle!) *Vlahakis (2006, in Variability of Blazars: Entering the GLAST Era) - Similar to model for OJ287 by Kikuchi et al. 1988 A&A, 190, L8 & Sillanpää et al. 1993, ApSS, 206, 55 - Polarization rotation was smooth  not turbulence as in 0420-014 (D’Arcangelo et al. 2007, ApJL)

14. BLLac in Late 2005: What Caused the Flares Interpretation: First optical/X-ray/TeV flare: knot Lorentz factor increases up to peak  Flare from increase in Doppler beaming - X-rays: synchrotron - No radio flare 2nd flare (includes radio): knot interacts with standing shock in 7 mm core - X-rays: SSC - Major radio flare

15. Interpretation of BL Lac Observations Shock follows spiral streamlines until it exits region of coiled magnetic field 1st flare occurs just before shock exits acceleration & collimation zone 2nd flare caused by moving shock interacting with standing shock(s) in core site of 1st flare site of 2nd flare

16. Sketch of Physical Structure of Jet, AGN Magnetic acceleration zone with helical field gives way to turbulence (in spine of jet) Transverse velocity gradients shear magnetic field, partially align it parallel to jet Outbursts of radiation - including X- and  -rays - occur in disturbances (probably shocks that become superluminal knots) as they pass through: (1) end of acceleration zone, (2) standing shock(s) farther downstream (e.g., the “core”), or (3) locations (time dependent) where jet bends closer to line of sight

17. Radio galaxies show a connection between X-rays from central engine region & activity in jet, ~ as in microquasars The FR I Radio Galaxy 3C 120 (z=0.033) HST image (Harris & Cheung) Scale: 1 mas = 0.64 pc = 2.1 lt-yr (Ho=70) Superluminal apparent motion, ~5c (~2 milliarcsec/yr) X-ray spectrum similar to Seyferts Mass of central black hole ~ 5x10 7 solar masses (Marshall, Miller, & Marscher 2004; Peterson et al. 2004) Sequence of VLBA images (Marscher et al. 2002)

18. X-Ray Dip/Superluminal Ejection Connection in 3C 120: Older data Superluminal ejections follow X- ray dips by ~ 60 days  Somewhat similar to microquasar GRS 1915+105 3mm core must lie at least 0.4 pc from black hole to produce the observed X-ray dip/superluminal ejection delay of ~ 60 days Marscher et al. 2002, Nature, 417, 625

19. X-Ray Dips/Ejections in 3C 120: Data since 2002 Superluminal ejections still follow X-ray dips by ~ 60 days Anti-correlation between X-ray flux or spectral index & 37 GHz flux - delay of 62 days

20. Comparison of GRS1915+105 with 3C 120 Light Curves + BH mass of 3C 120 ~4x10 6 times that of GRS 1915+105, so timescales of hours to months in 3C 120 are similar to the scaled-up quasi-periods (0.15 to 10 s) of 1915+105 +Typical fractional amplitude of dips is also similar - Random fluctuations higher amplitude in 3C 120 - Long, deep dips not yet seen in 3C 120, jet not seen during this stage of 1915+105 blow- up 150 s of blow-up should scale up to ~17 yr in 3C 120 if timescales  M bh  GRS 1915+105 over 3000 s on 9/9/97 Light curve (top) & PSD (bottom) (Taken from Markwardt et al. 1999 ApJL) Above: X-ray light curves of GRS 1915+105 over 150 s & 3C 120 over 5 yr

21. FR II Radio Galaxy 3C 111 (z=0.0485) Seems to Do the Same Ejection of bright superluminal knot follows start of X-ray dip by 0.35± yr 3mm core must lie at least 0.6 pc from black hole to produce the observed X-ray dip/superluminal ejection delay May 2004 August 2004 New knot 1 milliarcsec

22. FR II Radio Galaxy 3C 111 X-ray/Optical Correlation X-ray variations lead optical by 20 days - as expected if X-rays come from corona near black hole & optical from farther out in accretion disk

23. Connection between Disk + Jet Events Corona Possible scenarios of X-ray dip & hardening + faster jet flow → shock down jet: 1.Wind → jet; faster wind off disk → less dense corona, weaker X-ray, faster jet 2.B from ergosphere makes jet; fewer particles injected at base → weaker X-ray (if corona = base of jet), faster jet downstream (borrowed idea from G. Ghisellini) Flatter X-ray spectrum because downstream jet contributes higher fraction of X-rays when X-rays from base are weaker

24. Summary X-ray emission in the jet can occur in 2 or more sites: outer part of jet ’ s acceleration/collimation zone & standing shocks (or bends) At least some outbursts, flares, & pairs of flares come from superluminal knots Time delays between optical & X-ray sometimes consistent with shock model, sometimes with gradual e  acceleration 3C 120 and 3C 111 behave in a manner not ridiculously different from GRS1915+105 except that (1) we see no QPOs (2) we have yet to observe a prolonged low-hard state (3) the stage of 1915+105 with X-ray light curve most closely resembling 3C 120's has no observable jet  The physical connection between disk/corona/ & jet doesn't simply scale with black hole mass X-ray emission in the jet can occur in 2 or more sites: outer part of jet ’ s acceleration/collimation zone & standing shocks (or bends) At least some outbursts, flares, & pairs of flares come from superluminal knots Time delays between optical & X-ray sometimes consistent with shock model, sometimes with gradual e  acceleration 3C 120 and 3C 111 behave in a manner not ridiculously different from GRS1915+105 except that (1) we see no QPOs (2) we have yet to observe a prolonged low-hard state (3) the stage of 1915+105 with X-ray light curve most closely resembling 3C 120's has no observable jet  The physical connection between disk/corona/ & jet doesn't simply scale with black hole mass

25. BL Lac:Fit to EVPA Rotation Curvature of rotation: uniform rotation in source frame, axis at an angle of 45 o Can explain if streamline direction is aberrated (jet axis 7.7 o from l.o.s.; Jorstad et al. 2005 - J05)  Requires Lorentz factor ~ 7 (same as derived from knots by J05)  Magnetic helical pattern cannot be aberrated (Poynting flux advection speed not highly relativistic) without causing dominant polarization parallel to axis - consistent with stationary helical field pattern expected in MHD launched jets BL Lac in Late 2005: Fit to Optical EVPA Rotation