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 De Lotto - C2CR07 Lake Tahoe HESS VERITAS CANGAROO-III

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

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 Camera with 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%

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

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

Past observations: the Galactic Center 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 years no significant variability The high cutoff required by the data (> 10 TeV)  most SUSY DM scenarios rather unlikely  signal associated to astrophysical source (emission mechanism still unknown) HESS, PRL 97 (2006) 221102

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 galaxies with: high mass, low luminosity (M/L)  possible large DM content low stellar gas, dust content reduced background northern hemisphere  low Zd High M/L dwarf spheroid galaxies Draco De Lotto - C2CR07 Lake Tahoe ~20 h Draco and ~30 h 3EG_J1835+5918 observed up to now

Extragalactic VHE -ray sources 15 blazars & 1 radio galaxy MAGIC observations: Mrk 421 z=0.030 astro-ph /0603478 Mrk 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 AGN with relativistic jet aligned with observer’s line of sight non-thermal emission, highly variable Blazars: observer AGN are supermassive Black Holes in the center of mostly elliptical galaxies with a strong accretion of mass and jets emerging perpendicular to the accretion disk from the BH. Nearly half of all discovered cosmic VHE  sources are AGNs. Most of them show intense flaring at the highest  energy while there is no or very little variation in visible light emission. VHE -rays: leptonic or hadronic origin? Fast flares can be used for tests on light propagation Gamma Ray Horizon  cosmological parameters

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

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

known VHE sources new 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 Mkn 501 (z=0.034) 23.1 h in June/July ’05 14k excess events High variability Spectrum hardens with intensity De Lotto - C2CR07 Lake Tahoe 1ES2344+514 (z=0.044) Slope - 2.95 ± 0.12 1ES1959+650 (z=0.047) Slope: - 2.72 ± 0.14 Inverse Compton clearly observed in high-flux nights

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 Fuer QG limits: Tau limitiert auf 50sec+/- 50%, alle 3 symmetrisch 1.2-10 TeV Time (min)

Dispersion of light in vacuo 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. De Lotto - C2CR07 Lake Tahoe Caveat: blazars physical mechanisms (gradual e- acceleration in the emitting plasma) could explain the time delays Mkn 501 flare: assuming all g produced at the same moment EQG = (0.6 ± 0.2) 1017 GeV

new VHE sources PG1553+113 (z>0.09) MAGIC DISCOVERIES! PG1553 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]

The g-ray horizon at 10 GeV the universe becomes transparent Spectra affected by EBL absorption optical depth t De Lotto - C2CR07 Lake Tahoe Fazio-Stecker relation: (E,z) = 1 Distance estimator based on the absorption over g-ray path 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

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

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

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!

Conclusions Conclusions 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 De Lotto - C2CR07 Lake Tahoe

De Lotto - C2CR07 Lake Tahoe BACKUP

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

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 

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

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

De Lotto - C2CR07 Lake Tahoe

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.)

Constraining the EBL density (and paving the way to a measurement of cosmological parameters) Simulated measurements Mkn 421 Mkn 501 1ES1959+650 PKS2005-489 1ES1218+304 1ES1101-232 H2356-309 PKS 2155-304 H1426+428 GRH/GRH(WM=0.3,WL=0.0) 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

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

De Lotto - C2CR07 Lake Tahoe