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The MAGIC Collaboration

M ajor A tmospheric G amma-Ray I maging C herenkov Telescope International collaboration of 16 institutions from more than 10 countries, about 150 collaborators:

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The MAGIC Collaboration

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  1. Major Atmospheric Gamma-RayImagingCherenkov Telescope • International collaboration of 16 institutions from more than 10 countries, about 150 collaborators: • Barcelona IFAE, Barcelona UAB, Barcelona UB, Crimean Observatory, U.C. Davis, U. Lodz, UCM Madrid, MPI Munich, INFN/ U. Padua, INFN/ U. Siena, U. Humboldt Berlin, Tuorla Observatory, Yerevan Phys. Institute, INFN/U. Udine, U. Würzburg, ETH Zürich, INR Sofia, Univ. Dortmund The MAGIC Collaboration • Summary • Introduction: • MAGIC • Cycle I galactic targets • LS I +61 303 • Previous data • Discovery at VHE • Emission models

  2. MAGIC is a Imaging Air Cherenkov telescope operating in the energy range 50 GeV – 50 TeV • Located in the Roque de los Muchachos observatory, La Palma, Canary Island (Spain) at 28.8 N • Largest single-dish (17 m Ø)  lowest energy threshold • 576 high QE PMT camera with 3.5 Ø FOV • Good angular resolution~ 0.1 • Determination of point-like sources position within 2’ • Energy resolution 20-30% • Flux sensitivity: 2.5% Crab Nebula flux with 5s in 50h • Fast repositioning (<40s average) for GRB observation • Observations under moonlight possible  50% extra observation time The MAGIC telescope

  3. CRAB pulsar MAGIC HESS J1834 • Observations from November 2004 to May 2006 • About 25% total observation time for Galactic targets (apart from Crab Nebula) • Targets include: • SNR: • Intense EGRET sources • HESS galactic scan sources (HESS J1834, HESS J1813) • PWN • Pulsars: limits to Crab and PSR B1957 • Microquasars (low and high mass) • LS I +61 303 variable source • Galactic Center • HEGRA Unidentified TeV2032 • Cataclysmic variable (AE Aquari) Observation cycle I

  4. Artist’s view of mQSR

  5. Compacts jets Radio  IR  X?  gamma? (synchrotron) Disc + corona ? X therm + non therm Large scaleejection Radio & X gamma? Interaction with environment • Microquasars: • REXB displaying relativistic radio jets • Compact object Neutron Star or a Black Hole • In BH, the length and time scales are proportional to the mass, M. • The maximum temperature of the accretion disk is Tcol~2107M1/4 • Laboratories of jet physics • Possible contributors to galactic cosmic rays Microquasars

  6. X-ray and radio spectral states: • High/soft state steep power-law state. No radio emission. • Low/hard state (power-law state). Compact radio jet. • Intermediate and very high states  transitions. Transient radio emission. Spectral states

  7. 0.4 AU 0.7 0.5 0.3 To observer 0.9 0.2 0.1 • LS I +61 303: • High Mass x-ray binary at a distance of 2 kpc • Optical companion is a B0 Ve star of 10.7 mag with a circumstellar disc • Compact object probably a neutron star • High eccentricity or the orbit (0.7) • Modulation of the emission from radio to x-rays with period 26.5 days attributed to orbital period • Secondary modulation of period 4 years attributed to changes in the wind flow • Compact jets (100 AU) resolved with radio observations  microquasar LS I +61 303

  8. periastron periastron 0.4 AU 0.7 0.5 0.3 Paredes et al. 1990 To observer 0.9 Photon index 0.2 0.1 X-ray flux Radio flux Greiner & Rau 2001 • Periodic radio outbursts at phases 0.5-0.8 (close to apastron), with intensity and peak position modulated with a 4 yr period • X-ray outburst observed ~10 days (DF~ 0.4) before radio outbursts • A significant hardening of the x-ray spectrum is observed on the radio onset LS I +61 303: radio and x-ray 3s

  9. F = 0.67-0.68 F = 0.71-0.72 Massi et al 2004 • Double sided jets at milli-arsec scale (~200 AU) are resolved with radio interferometer MERLIN (5 GHz) • The jets display fast precession LS I +61 303: radio jets • The projected angle changes by ~60 in 24 hours • The feature on the second day can be associated with the jet of the day before compatible with a velocity of 0.6c

  10. Hartman et al. 1999 Massi et al. 2004 Tavani et al. 1998 • A HE g-ray (100 MeV – 10 GeV) source detected by EGRET is marginally associated with the position of LS I +61 303. • The emission is variable and peaking at periastron passage (f=0.2) and f~ 0.5-0.6 LS I +61 303: g-rays • Interpreted as stellar photons upscattered (inverse Compton) by relativistic electrons in the jet

  11. MAGIC has observed LS I +61 303 for 54 hours from November 2005 to March 2006 (6 orbital cycles) LS I +61 303 at Very High Energies Albert et al. 2006 • A point-like source (E>200GeV) detected with significance of ~9s • Position: RA=2h40m34s, DEC=6115’ 25” [0.4’ (stat), 2’ (syst)] in agreement with LSI position  identification of g-ray source • The source is quiet at periastron passage and at relatively high emission level (16% Crab Nebula flux) at later phases [0.5-0.7]

  12. MAGIC has observed LSI during 6 orbital cycles • A variable flux (probability of statistical fluctuation 310-5) detected • Marginal detections at phases 0.2-0.4 • Maximum flux detected at phase 0.6-0.7 with a 16% of the Crab Nebula flux • Strong orbital modulation  the emission is produced by the interplay of the two objects in the binary • No emission at periastron, two maxima in consecutive cycles at similar phases  hint of periodicity! Flux time variability Albert et al. 2006

  13. LS I +61 303: the film Albert et al. 2006 • The average emission has a maximum at phase 0.6. • Search for intra-night flux variations (observed in radio and x-rays) yields negative result • Marginal detections occur at lower phases. We need more observation time at periastron passage • Parts of the orbit not covered due to similarities between orbital period (26.5 days) and Moon period

  14. Contemporaneous radio observations Albert et al. 2006 • We perform contemporaneous radio observations (Ryle telescope 15GHz) during the last observed orbital cycle • Two maxima are detected: just before periastron and higher at phase 0.7 • TeV peak is observed one day before

  15. Energy spectrum Albert et al. 2006 • The average energy spectrum from 200 GeV to 4 TeV is well fitted by a power law with spectral index a = -2.6  0.2 (stat)  0.2 (syst) • The luminosity above 200 GeV is ~7 x 1033 erg s-1 (assuming a distance of 2 kpc) ~ 6 times that of mQSR LS 5039 (average) • It displays more luminosity at TeV energies than at x-rays

  16. Broad band spectrum Chernyakova et al. 2006 • 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

  17. More multi-wavelength observations are needed, mainly VHE+radio Mirabel 2006 Mirabel 2006 • 1. Microquasar:Particles accelerated in the jet collide with stellar or synchrotron photons by inverse Compton scattering, boosting their energies to the TeV range. Similar to quasar. Pros: steady, double sided radio jets resolved; similar object known (LS 5039) Cons: No spectral cut-off from accretion disk is observed. No emission at periastron • 2. Binary pulsar: the g-rays are produced by the interaction of the winds of a young pulsar with that of the Be star Pros: spectral shape and time variability resembles that of young pulsars; similar object known PSR B1259-63 Cons: no pulsed emission; radio jets; Alternative emission models

  18. In the microquasar scenario, two alternative g-ray production mechanisms are possible: • Inverse Compton scattering: e + g→ e + g relativistic electrons from the jet with the star of synchrotron photons • Hadron interactions: p + p → X + p0 └→ g g relativistic protons in the jet interact with non-relativistic stellar wind ions,producing gamma-rays via neutral pion decay • Our result seems to favor the leptonic scenario since g-rays are produced at phase 0.5-0.6 i.e far from the companion star, and there the efficiency of the leptonic process is likely higher that that of the hadronic process • In either case opacity seems to play a major role near periastron (e.g. by gamma-ray cascading) • Neutrinos are expected to be produced in a hadronic scenario (from the decay of charged pions and muons) and would be unabsorbed. • Differences in the spectral shape are also expected. Leptonic vs haroncic More g-ray data and Multi-messenger observations are needed!

  19. The MAGIC IACT has completed its first observation cycle in May 2006 • 25% of the observation time has been devoted to Galactic objects • We have detected 5 TeV sources out of which a new discovery • The microquasar LS I +61 303 has been detected at TeV energies • The emission is variable • Possible hint of periodicity • The maximum of the emission happens 1/3 of the orbit away from periastron • New MAGIC+multi-wavelength/messenger will establish LSI nature and the mechanism of VHE g-ray production Conclusions

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