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Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration

Selected topics & results. OUTLINE: The telescope Dark Matter searches Extragalactic sources Gamma Ray Bursts. Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration C2CR07 – Lake Tahoe. Current generation Cherenkov telescopes. MAGIC.

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Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration

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  1. Selected topics & results • OUTLINE: • The telescope • Dark Matter searches • Extragalactic sources • Gamma Ray Bursts Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration C2CR07 – Lake Tahoe

  2. Current generation Cherenkov telescopes MAGIC De Lotto - C2CR07 Lake Tahoe HESS VERITAS CANGAROO-III

  3. The MAGIC site De Lotto - C2CR07 Lake Tahoe MAGIC MAGIC and its Control House La Palma, IAC 28° North, 18° West 2200 m asl

  4. The MAGIC-ray telescope Barcelona IFAE, UA Barcelona, U. Barcelona, HU Berlin, Instituto Astrofisica Canarias, U.C. Davis, U. Dortmund, U. Lodz, UCM Madrid, MPI München, INFN/ U. Padua, INFN/ U. Siena, INR Sofia, Tuorla Observatory, Yerevan Phys. Institute, INFN/ U. Udine, U. Würzburg, ETH Zürich De Lotto - C2CR07 Lake Tahoe • Largest Cherenkov Telescope:17 m Ø mirror dish • 3.5° FoV Camerawith 576 enhanced QE PMT’s • Fast repositioning for GRBs:average < 40 s • Trigger threshold:50 GeV • Sensitivity:2.5% Crab / 50 h • -PSF:~ 0.1° • Energy resolution:20 - 30%

  5. VHE -ray physics overview -quasar galactic center pulsar AGN pulsar windnebula GRBs shelltype SNR cosmological -ray horizon origin of cosmic rays cold dark matter quantum gravity effects De Lotto - C2CR07 Lake Tahoe > 30 sources above 100 GeV, rapid growth in recent years

  6. -ray emission from Dark Matter q  Z,H  q CDM density: Particlephysics: signature for IACTs: g-ray flux ~ r2 => search for CDM clumps observe: galactic center (high diffuse g bkg),other dense objects g-line Eg = mc g-line Eg = mc- mZ2/4 mc g continuum g-linessuppressed g-continuum with E << m dominates • Standard Cosmological scenario of Cold Dark Matter De Lotto - C2CR07 Lake Tahoe • Neutralino(lightest SUSY particle) attractive candidate g-flux from c annihilations:

  7. Past observations: the Galactic Center The high cutoff required by the data (> 10 TeV) most SUSY DM scenarios ratherunlikely  signal associated to astrophysical source (emission mechanism still unknown) HESS, PRL 97 (2006) 221102 ApJ L638 (2006) 101 De Lotto - C2CR07 Lake Tahoe • Clear VHE signal: • UNCUT power law spectrum up to > 10 TeV:spectral slope: -2.2 ± 0.2 • (in good agreement with HESS) • steady signal over 2 yearsno significant variability

  8. Proposals of candidates for observations (> June 2006) • “Mini-spike” model • [Bertone, Zentner, Silk, Phys. Rev. D72 (2005) 103517] • Possible formation of high r DM regions in association with Intermediate-Mass Black Holes in the galactic halo • Unidentified EGRET sources (>100): • high galactic latitude(more clean signal) • stable flux • no counterpart at large wavelengths • Look for identical cut-offs (DM mass) and similar spectra • Nearby galaxieswith: • high mass, low luminosity (M/L) •  possiblelarge DM content • low stellar gas, dust content • reduced background • northern hemisphere low Zd • High M/Ldwarf spheroidgalaxies • Draco De Lotto - C2CR07 Lake Tahoe ~20 h Draco and ~30 h 3EG_J1835+5918 observed up to now

  9. Extragalactic VHE -ray sources observer Blazars: • AGNwith relativistic jetaligned with observer’s line of sight • non-thermal emission, highly variable 15 blazars & 1 radio galaxy • MAGIC observations: • Mrk 421 z=0.030 astro-ph /0603478Mrk 501 z=0.034 astro-ph 0702008 • 1ES2344+514 z=0.044 astro-ph /0612383 • Mrk 180 z=0.045 ApJL 648 (2006) 105 • 1ES1959+650 z=0.047 ApJ 639 (2006) 761 • 1ES1218+308 z=0.182 ApJL 642 (2006) 119 • PG1553+113 z>0.09 ApJL 654 (2007) 119 • 3 more in pipeline De Lotto - C2CR07 Lake Tahoe redshift • VHE -rays: leptonic or hadronic origin? • Fast flares can be used for tests on light propagation • Gamma Ray Horizon • cosmological parameters

  10. Focus on particular features Light curves g-ray fluxes as a function of time Differential energy spectra most follow a pure power law De Lotto - C2CR07 Lake Tahoe 2 min bin 1ES1959+650 slope: - 2.72 ± 0.14- 3.2 ± 0.2

  11. Attenuation of VHE -rays 2.7K gVHEgEBL e+e- Red shifted stellar light Red shifted dust light x x x De Lotto - C2CR07 Lake Tahoe • Absorption leads to cutoff in spectrum • Measurement of spectral features allows to constrain EBL models

  12. known VHE sourcesnew effects, increased knowledge • Mkn 421 (z=0.030) • Slope: -2.20±0.08 (hardens with intensity) • cutoff 1.1 -1.6 TeV • TeV-Xray correlation De Lotto - C2CR07 Lake Tahoe Mkn 501 (z=0.034) • 23.1 h in June/July ’05 • 14k excess events • High variability • Spectrum hardens with intensity 1ES2344+514(z=0.044) Slope - 2.95 ± 0.12 1ES1959+650(z=0.047) Slope: - 2.72 ± 0.14 • Inverse Comptonclearly observed • in high-flux nights

  13. High time-resolution study of Mkn 501 flare 0.15-0.25 TeV De Lotto - C2CR07 Lake Tahoe • Unprecedented fast variations • Doubling time < 5 min • Spectrum shape changes within minutes: • implications on the dispersion relation for light 0.25-0.6 TeV 0.6-1.2 TeV 1.2-10 TeV Time (min)

  14. Dispersion of light in vacuo De Lotto - C2CR07 Lake Tahoe • In some QG approaches [Amelino-Camelia 1998] : Dv/c ~ E / EQG, EQG~EP ~ 1019 GeV • At 1st order, the arrival delay of g-rays emitted simultaneously from a distant source should be proportional to their energy difference and the path L to the source: • The expected delay is very small and to make it measurable one needs to observe very high energy g-rays coming from sources at cosmological distances. => new, stronger constraints on emission mechanism and light-speed dispersion relations could come from high time-resolution studies of AGN flares. Mkn 501 flare: assuming all g produced at the same moment EQG = (0.6 ± 0.2) 1017 GeV Caveat:blazars physical mechanisms (gradual e- acceleration in the emitting plasma) could explain the time delays

  15. new VHE sources PG1553 MAGIC DISCOVERIES! • PG1553+113 (z>0.09) • HESS: 4.0 hint (A&A 448L (2006)) • MAGIC: 8.8 from 19h observation in 2005-06 • Steepest observed g-ray spectrum: Mkn 180 (z=0.045)slope: - 3.3 ± 0.7 De Lotto - C2CR07 Lake Tahoe New Sources • 1ES1218+304(z=0.182) • Upper limits from HEGRA, WHIPPLE • Jan 2005, 8.2 h, 6.4  slope: - 3.0 ± 0.4 slope: - 4.2 ± 0.3 • Upper limit of z < 0.42 using MAGIC+HESS spectra • [Mazin & Goebel ApJL 655 (2007) 13]

  16. The g-ray horizon De Lotto - C2CR07 Lake Tahoe Spectra affected by EBL absorption optical depth t Distance estimator based on the absorption over g-ray path Fazio-Stecker relation: (E,z) = 1 • If model assumptions on EBL • possibility of accessing cosmological parameters • [ Blanch & Martinez, Astropart.Phys.23 (2005) 598] old generation IACTs MAGIC, HESS future IACTs • at 10 GeV the universe becomes transparent

  17. Gamma Ray Bursts Brightest, most violent known phenomena Origin still unclear Short (0.1 – 100 s) Needfast repositioningafter GRB alert Origin at cosmological distances => High energy -rays will be absorbed by EBL => Need low energy threshold De Lotto - C2CR07 Lake Tahoe GRB Positions in Galactic Coordinates, BATSE Only to be seen by all sky monitor detectors Acc. by MAGIC DURATION OF GRBs

  18. GRBs and MAGIC • MAGIC is the right instrument, due to its fast movement & low threshold • MAGIC is in the GCN Network • GRB alert active since Apr 2005 De Lotto - C2CR07 Lake Tahoe 13

  19. GRB observation with MAGIC GRB050713a ApJ L641 (2006) 9 De Lotto - C2CR07 Lake Tahoe MAGIC data-taking GRB-alarm from SWIFT • No VHE g emission from GRB positively detected yet... • (all other observed GRB very short or at very high z) We are on the track!

  20. Conclusions Conclusions De Lotto - C2CR07 Lake Tahoe • MAGIC is delivering very good physics results • detected ~15 sources (galactic sources not covered in this talk) • discovered 4 new VHE -ray sources • 17 scientific publications (printed or submitted) • Cycle2 almost completed: important commitment to test fundamental physics (DM, Lorentz violation, …) • A second telescope will see the first light soon (end 2007) 2 x better sensitivity  no. of sources may increase up to ~50

  21. BACKUP De Lotto - C2CR07 Lake Tahoe

  22. Incoming g-ray Hadron Particle shower ~ 10 km ~ 1o Gamma Cherenkov light ~ 120 m Observational Technique De Lotto - C2CR07 Lake Tahoe

  23. The threshold • We are publishing with a threshold of 70 GV • We detect significant signal above 40 GeV • Understanding our efficiency towards the goal of 40 GeV. A special task force (UHU) has been set up; preliminary physics results at 50 GeV. • Substantial improvement on DM studies and determination of cosmological constants De Lotto - C2CR07 Lake Tahoe Secret 

  24. TeV blazars • Active Galactic Nuclei: • • Extragalactic sources • • Small fraction of observed galaxies harbor active nuclei • • Supermassive black hole ole of 106 – 1010 solar masses • • Relativistically rotating accretion disk • Emission of collimated relativistic jets • Blazars: • • Strong nonthermal radiation • • High variability at all wavelenghts • • Jets viewed under small angle • • High Doppler factors expected: Jets may • attain high luminosities Lobs~L d4 De Lotto - C2CR07 Lake Tahoe g-rays are messenger particles particles, revealing properties of: • Leptonic acceleration • Hadronic acceleration in the jets

  25. Absorption of extragalactic  - rays Any  that crosses cosmological distances through the universe interacts with the EBL De Lotto - C2CR07 Lake Tahoe Attenuated flux function of g-energy and redshift z. For the energy range of IACTs (10 GeV-10 TeV), the interaction takes place with the infrared (0.01 eV-3 eV, 100 m-1 m). Star formation, Radiation of stars, Absorption and reemission by ISM EBL By measuring the cutoffs in the spectra of AGNs, any suitable type of detector can help in determining the IR background-> needs good energy resolution Acc. by new detectors

  26. De Lotto - C2CR07 Lake Tahoe

  27. AGN at a glance De Lotto - C2CR07 Lake Tahoe At least a handle on EBL but also the possibility of accessing cosmological constants (Martinez et al.) could become reality soon (maybe including X-ray obs.)

  28. Constraining the EBL density (and paving the way to a measurement of cosmological parameters) PKS 2155-304 H1426+428 H2356-309 PKS2005-489 1ES1218+304 1ES1101-232 1ES1959+650 Mkn 421 Mkn 501 GRH/GRH(WM=0.3,WL=0.0) Simulated measurements De Lotto - C2CR07 Lake Tahoe Blanch & Martinez 2004 Different EBL models Simulated measurements Mkn 421 Mkn 501 1ES1959+650 PKS2005-489 PKS 2155-304 H1426+428 1ES1218+304 1ES1101-232 H2356-309

  29. Energy spectrum • The absence of a spectral feature between 10 and 100 keV goes against an accretion scenario • Contemporaneous multiwavelength observations are needed to understand the nature of the object De Lotto - C2CR07 Lake Tahoe Albert et al. 2006

  30. De Lotto - C2CR07 Lake Tahoe

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