1. R. M. Wagner: AGN observations with MAGIC – p.1 R. M. W AGNER Max-Planck-Institut für Physik, München on behalf of the MAGIC C OLLABORATION AGN Observations in the GeV/TeV Energy Range with the MAGIC Telescope

2. R. M. Wagner: AGN observations with MAGIC – p.2 Contents Blazars & jets – how can TeV observations help? MAGIC blazar observation activities Blazars observed by MAGIC, some highlights Markarian 421 1ES 1959+650 1ES 1218+304 PG 1553+113 Markarian 501 Markarian 180 1ES 2344+514 BL Lacertae Conclusions 16 sources (incl M87) to date and counting seen in VHE  -rays

3. R. M. Wagner: AGN observations with MAGIC – p.3 Jets observed under small angle Rapid variability at all wavelengths Most violent and rapid often in VHE High Doppler factors: amplified emission, deep insight into jet Kino et al. synchrotron peak Inverse Compton peak (Buckley 1999) Hadronic TeV Blazars | E>100 GeV Mkn 501 HEGRA, Kranich 2001 How can TeV observations help?  -rays are crucial messengers: Dynamics of emission regions in the jets Study acceleration & energy loss timescales Decide: leptonic vs hadronic acceleration? -Hadronic models challenged by observed X/VHE correlations and by very rapid  -ray variability -Variability needs to be explained: Matter crossing the jet? sub-shocks?...jet structure Decide SSC/EIC

4. R. M. Wagner: AGN observations with MAGIC – p.4 The MAGIC Telescope 17m  Imaging Air Cherenkov Telescope: currently largest single-dish instrument 3.5°  FOV Optimized for extragalactic point-like sources Trigger threshold: 50 – 60 GeV Analysis thresh: 70 – 100GeV Energy resolution 30% at 150 GeV Sensitivity: 2.5% Crab Nebula in 50 hours at E=250 GeV Enhanced duty cycle (moon observations) 2nd telescope under construction Major Atmospheric Gamma-ray Imaging Cherenkov Telescope  Extensive blazar observation program: approx. 500 hours/year  Simultaneous optical monitoring during observations  MWL campaigns with Suzaku and other satellite experiments (results: see ICRC’07)  Numerous ToO agreements with optical; X-ray,  -ray satellites; telescopes, and  Global Network of Cherenkov Telescopes initiative  simultaneous observations w/HESS: wider energy coverage  sequential observations w/VERITAS: ext’d time coverage  Ongoing blazar monitoring of known bright sources: low state, flare statistics, blazar duty cycle MAGIC | AGN & blazar observation activities

5. R. M. Wagner: AGN observations with MAGIC – p.5 Mkn 421 | z=0.030 | Nov 2004 - Apr 2005 25.6 h observations, clear diurnal signal Energy threshold: 150 GeV Source-inherent cutoff 1.4 ± 0.3 TeV ApJ 663 in press astro-ph/0603478 historical TeV spectra MAGIC

6. R. M. Wagner: AGN observations with MAGIC – p.6 Mkn 421 | z=0.030 | Nov 2004 - Apr 2005 Variable fluxes on day-to-day scale, 0.5–2 Crab, but no flares shorter than 1h ApJ 663 in press astro-ph/0603478 F(E>200GeV) 2-10 keV optical Intra-night, 10 min bins: 6 nights, night-by-night Clear TeV/X-ray correlation, slope hardens with intensity: IC favored

7. R. M. Wagner: AGN observations with MAGIC – p.7 Mkn 501 | z=0.034 | June/July 2005 ApJ submitted astro-ph/0702008 Clear signal each night: > 85  Energy threshold 150 GeV No strong evidence for correlated optical/X/VHE emission June 30 July 09 Clear variability in  -rays Mkn501 ~ 0.5 Crab (‘low’) Unprecedented fast variations! (<3 min) Emission region severely constrained! June 30July 09 Mkn 501 2 min bins Obs during moontime!

8. R. M. Wagner: AGN observations with MAGIC – p.8 Mkn 501 | Intra-night flares ApJ submitted astro-ph/0702008 Two flares behave rather differently June 30 flare: No high (>600 GeV) energies July 09: all energies, “pre-flare“? June 30 July 09 150-250 GeV 250-600 GeV 600-1200 GeV 1200 GeV and above

9. R. M. Wagner: AGN observations with MAGIC – p.9 Constant fit :  2 /ndf = 76.6/25 (P=4×10 -7 ) Spectrum hardens with increasing flux Peak Peak in VHE distribution clearly observed in high-flux nights Peak location seems to depend on the source luminosity Mkn 501 | Spectral variations EBL corrected (Kneiske et al. 2004 “low IR”) measured ApJ submitted astro-ph/0702008 Flux-Spectral index correlationSED MAGIC

10. R. M. Wagner: AGN observations with MAGIC – p.10 1ES 2344+514 | z=0.044 | Aug 2005 – Dec 2005 ApJ 663 in press astro-ph/0612383 First time-resolved observation of the low blazar emission state Energy spectrum Discovery: Whipple, Flare Dec 1995, F (>350GeV) = 63% Crab Catanese et al. 1997 UL from Whipple (1997, 2000), HEGRA (1998-2002), TACTIC (2004-2005) MAGIC: observation Aug-Dec 2005 F(>350GeV)=6% Crab 11  - Clear detection Only marginal hints of variability

11. R. M. Wagner: AGN observations with MAGIC – p.11 PG 1553+113 | z>0.09 ApJL 654 (2007) 119 Blazar at unknown distance No emission lines: Jet outshines core? Very close alignment of jet axis to observer? High z? Small host galaxy? Discovery by H.E.S.S. & MAGIC Steepest observed  –ray spectrum: spectral slope  =4.2±0.3 – how much absorption is intrinsic? MAGIC VHE KVA optical 2005 2006 SSC modeling: Models based on different z: Disfavor z>0.56 on 4.5  level Light curve: No correlation with optical flare. Time lag?

12. R. M. Wagner: AGN observations with MAGIC – p.12 BL Lacertae | z=0.069 | Aug – Dec 2005 LBL-type blazar: Synchrotron peak in the optical: Expect steep slope at VHE  profit from low energy threshold!  First LBL discovered in VHE  –rays!  Relatively steep  –ray spectrum: spectral slope  =3.6±0.5 ApJL submitted astro-ph/0703084  Leptonic model, no EIC components necessary as required to explain 1997 flare seen by EGRET E peak =250 GeV 216 Excess events Significance: 5.1  Sky map Ravasio et al. 2002 O/VHE correlation?

13. R. M. Wagner: AGN observations with MAGIC – p.13 Summary & Conclusions There are now 16 blazars observed in  -rays above 100 GeV with more observations & detections in the pipeline VHE observations are crucial for modeling non-thermal emission regions in jets, but... Will need full time-dependent modeling & MWL observations Increased instrumental sensitivity helps precision observations of bright blazars Mkn 421, Mkn 501, 1ES 2344. Leptonic nature of acceleration? flux-hardness correlation, IC peak detected Fast blazar flaring: First time minute-scale variability in VHE! Low blazar emission state was mostly elusive before: now removing observational bias towards flaring sources in the VHE regime Many new sources discovered with interesting properties: Mkn 180: source detected upon optical trigger 1ES 1218: high redshift (now confirmed by VERITAS) PG 1553: probably very close alignment to jet axis BL Lacertæ: First LBL  -ray source

14. R. M. Wagner: AGN observations with MAGIC – p.14 Backup slides

15. R. M. Wagner: AGN observations with MAGIC – p.15 Detection of E>100 GeV  -rays  showers Narrow images Aligned towards source direction , 100 GeV Proton, 100 GeV Cosmic rays initiate extensive air showers Cherenkov light is emitted by relativistic particles in the shower Showers induced by  -rays and hadronic cosmic rays (  10 4 times more numerous) develop differently in the atmosphere Image parametrization Background suppression: Cuts in image parameters  candidate events from pointing direction hadronic showers Spread images Isotropic arrival direction

16. R. M. Wagner: AGN observations with MAGIC – p.16 Kino et al. synchrotron peak Typical Spectral Energy Distribution Inverse Compton peak (Buckley 1999) Inverse Compton scattering on different possible target photon fields In particular in blazars: Synchrotron Self-Compton model: synchrotron photons target field for IC process Natural explanation of X-ray /  -ray correlated variability Acceleration and VHE  production Primary acceleration by diffusive shock acceleration in jets  Power law Electrons emit synchrotron radiation  Electron      Protons:  0 decay from photo-pion production or synchrotron emission from protons Difficult to accomodate X-ray /  -ray correlations Should observe simultaneous -emission Hadronic acceleration models:

17. R. M. Wagner: AGN observations with MAGIC – p.17 Low-level blazar emission 1ES 2344+514 Discovery: Flare during the night of 1995/12/21 Up to now VHE  -ray observations biased towards flaring states: What are the properties of blazars at non-flare times? MAGIC: Clear 11  signal from 23 observation nights MAGIC 2005 VHE  -ray light curve and with previous <5  observations Profit from MAGIC’s higher sensitivity Integral flux 5.7 times lower than during 1995 flare Light curve well compatible with low emisson state of the source All-time VHE  -ray light curve 1995 flare MAGIC significance well below 5  1995 flare data & 2005 MAGIC low emission data could be modeled using a one-zone SSC model. ApJ in press astro-ph/0612383

18. R. M. Wagner: AGN observations with MAGIC – p.18 PG 1553 probably distant source! Possibility to constrain redshift by assumptions on EBL and acceleration mechanism: z < 0.42 (Mazin & Goebel 2007) Once distance is known: Source probably decisive for EBL determination! Attenuation of VHE  -rays in the universe PG 1553+113 blazar with unknown distance Simultaneous discovery by MAGIC, H.E.S.S. MAGIC: 8.8  signal from 19 h observations Steepest observed  –ray spectrum: spectral slope  =4.2  0.3 MAGIC H.E.S.S. Crab nebula Modification of spectrum due to Extragalactic Background Light (EBL)  VHE +  EBL  e + e –  VHE is “lost” to observer IR (dust) Vis (starlight) Peak in  e + e –  GeV energies probe a specific energy range of the EBL spectrum Net effect in the >100 GeV range: Steepening of (power-law) spectra

19. R. M. Wagner: AGN observations with MAGIC – p.19 Mkn 180 | z=0.045 | 2006 March 23-31 New sources discovered by IACT: Mkn 180 Successful optical trigger 11.1 h, 5.5 , F (>200GeV) = 11% Crab, spectral slope  =3.3 ± 0.7 rather hard spectrum Earlier UL at comparable level No significant variability Need to understand whether O/VHE correlation ApJL 648 (2006) 105 SED Model: FO98 Model: CG02

20. R. M. Wagner: AGN observations with MAGIC – p.20 1ES1218+304 | z=0.182 Whipple: F (>350GeV) <8% C.U. HEGRA: F (>750GeV) <12% C.U. MAGIC: DISCOVERY! Jan 2005, 8.2 h 6.4 , F >120GeV = 13% C.U., spectral slope  =–3.0 ± 0.4  2 plot sky map ApJL 642 (2006) 119 SED

21. R. M. Wagner: AGN observations with MAGIC – p.21 High-peaked BL Lac objects Cycle-I: 181 hours, 13 source candidates Cycle-II: 99 hours Low-peaked BL Lac objects Cycle-I: 76 hours Cycle-II: 86 hours Monitoring of TeV-bright blazars Cycle-II: 38 hours (70% done) Time-of-Opportunity observations (externally triggered) Cycle-II: 11 hours Upper limit publication of cycle-I HBLs upcoming... MAGIC blazar observations