1. Incontri di Fisica delle Alte Energie IFAE 2006 Pavia Vincenzo Vitale Recent Results in Gamma Ray Astronomy with IACTs

2. Introduction Instruments and techniques Scientific highlights and observations Summary Outline

3. Introduction Cosmic gamma-ray observation: - directly from satellites (HE) < O(10 GeV) and - indirectly from ground-based installations (VHE) > O(100 GeV) Satellites: EGRET -> HE gamma-ray astronomy already consolidated. EGRET: Around 350 sources (250 unidentified)

4. Ground based vs satellite Satellite : primary detection small effective area ~1m 2 lower sensitivity large angular opening large duty-cycle large cost lower energy low bkg IACT/ground based Secondary detection huge effective area ~10 4 m 2 Higher sensitivity small angular opening small duty-cycle low cost high energy high bkg

5. Sensitivity of γ detectors High galactic latitudes  b =2 10 -5  cm -2 s -1 sr -1 (100 MeV/E) 1.1 ). Cerenkov telescopes sensitivities (Veritas, MAGIC, Whipple, Hess, Celeste, Stacee, Hegra) are for 50 hours of observations.Large field of view detectors sensitivities (AGILE, GLAST, Milagro, ARGO, AMS) are for 1 year of observation.

6. STACEE CACTUS MILAGRO TIBET ARGO-YBJ PACT GRAPES TACTIC VERITAS MAGIC HESS CANGAROO TIBET MILAGRO STACEE TACTIC VHE γ detectors

7. Observation tecnique ~ 10 km Particle shower Detection of TeV gamma rays using Cherenkov telescopes ~ 1 o Cherenkov light ~ 120 m

8. Image intensity  Shower energy Image orientation  Shower direction Image shape  Primary particle

9. Better bkgd reduction Better angular resolution Better energy resolution Slide fro Pr W. Hofmann

10. Galactic Sources  Acceleration of Galactic cosmic rays in SNR  Galactic center emissions  New type of sources

11. HESS galactic plane survey 330° Sources > 6 sigma: 9 new, 11 total Sources > 4 sigma: 7 new Most sources: Shell-type SNR Pulsar-Wind- Nebulae Unidentified New objects

12. RX J1713-3946  Unambiguous evidence for particle acceleration in an SNR shell  Resolved shell in VHE g-rays  Close correlation between X-rays and g-rays

13. RX J1713-3946 Preliminary Index ~ 2.1 – 2.2 Little variation across SNR No evidence of cutoff or break at high energy  Acceleration of primary particles in SNR shock to well beyond 100 TeV

14. Galactic Center Sgr A Diffuse emission Nature, Feb. 9th 2006

15. Galactic Center Unbroken power law, index 2.3 Good agreement between HESS and MAGIC (large zenith angle observation ).

16. PSR B1259-63  Binary system  Strong stellar wind  Shock at wind- pulsar interaction

17. Extragalactic Sources  Physics of AGN jets  Cosmological extragalactic background light (EBL)

18. AGN summary SourceRedshiftType First Detection Confimation M870.004 FR I HEGRAHESS Mkn 421 0.031 BL Lac WhippleMany Mkn 501 0.034 BL Lac WhippleMany 1ES 2344+514 0.044 BL Lac WhippleHEGRA 1ES 1959+650 0.047 BL Lac Tel. Array Many PKS 2005-489 0.071 BL Lac HESS PKS 2155-304 0.116 BL Lac Mark VI HESS H1426+4280.129 BL Lac WhippleMany H2356-3090.165 HESS 1ES 1218+304 0.182 BL Lac MAGIC 1ES 1101-232 0.186 BL Lac HESS

19. Extrag. Background Light  Cosmological radiation from star formation and evolution.  Spectral signature from gg absorption for Eg ~ 50-2000 GeV.  Use measured AGN spectra to constrain EBL. 1ES 1101-232 (HESS col.) Gamma ray horizon Martinez et al 2005

20. AGN with orphan flares  Source observed already by Whipple and HEGRA in flaring state.  Orphan flares (hadronic origin ?)  MAGIC observation: low threshold and low flux (low state).  Two neutrinos in AMANDA data ?.  Two HiRes stereo events ?.  => Connection btw. Gamma-ray astronomy and neutrino/UHECR astronomy ?.

21. High resolution flare study Huge Mkn 501 flare on 1st July 2005 -> 4 Crab intensity. Intensity variation in 2 minute bins -> new, much stronger, constraints on emission mechanism and light-speed dispersion relations (effective quantum gravity scale). Preliminary 2 minutes time bins Preliminary Crab

22. GRBs observation with MAGIC # GRB Event Satellite Onset [UTC] Dt alert [sec] Dt obs. [sec]q[deg]z1GRB050408HETE16:22:50143138481.23 2GRB050421SWIFT04:11:525811252 3GRB050502SWIFT02:14:1818990333.79 4GRB050505SWIFT23:22:21540793504.27 5GRB050509ASWIFT01:46:291611557 6GRB050509BSWIFT04:00:1915368690.23 7GRB050528SWIFT04:06:45437752 8GRB050713ASWIFT04:29:02134049 On 13 July 2005 MAGIC has observed a GRB with only 40 s delay Preliminary analysis shows no signal Constrain models on prompt emission

23. Mrk421 Mrk501 Crab Pulsar AGN The VHE γ ray sky + some additional sources in galactic plane. 1995 2005

24. Source Counts Source Type* 20032005 Pulsar Wind Nebula (e.g. Crab, MSH 15-52 …) 16 Supernova Remnants (e.g. Cas-A, RXJ 1713 …) 26 Binary Pulsar (B1259-63) 01 Micro-quasar (LS 5039) 01 Diffuse (GC clouds) 01 AGN (e.g. Mkn 421, PKS 2155 …) 711 Unidentified26 TOTAL1232  Explosion in the number of VHE sources.

25. Summary  Galactic Plane rich in number and type of VHE emitters.  PWN and SNRs firmly established as TeV sources.  Unprecedented spectrum and morphology studies.  Discovery of VHE gamma-ray emission from a binary Pulsar and from a Microquasar.  Wide-range spectrum of gamma-ray emission from GC. No hint for DM annihilation signals.  Increased number of TeV blazars at large redshift. Constraints in cosmological EBL.  2 minutes-resolution light-curve of a fast flare. Constraints in emission models and light-speed dispersion relations.  First GRB follow-up in coincidence with X-ray observation. Constraints in GRB models.

26. γ /hadron separation  CR (2) Shape:  –rays are narrower than cosmic rays.

27. γ /hadron separation Proton shower Gamma shower Crab Nebula

28. New Cherenkov Telescopes HESS-II New 28m telescope. 2048 pixel camera. Lower energy 40-50 GeV First light in 2008. MAGIC-II Improved 17m telescope. Faster FADCs and a high-QE camera. First light in 2007. MAGIC-I MAGIC-II 85m VERITAS 4x 12m telescopes at Kitt-Peak in 2006.