Results of MAGIC first observation cycle on Galactic sources Javier Rico for the MAGIC Collaboration Institut de Física d’Altes Energies Barcelona, Spain THE MULTI-MESSENGER APPROACH TO UNIDENTIFIED GAMMA-RAY SOURCES Barcelona (Spain) July 4 - 7, 2006

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources The MAGIC Collaboration Major Atmospheric Gamma-Ray Imaging Cherenkov 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 Summary Introduction: MAGIC Cycle I galactic targets LS I Previous data Discovery at VHE Emission models

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources The MAGIC telescope 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 5  in 50h Fast repositioning (<40s average) for GRB observation Observations under moonlight possible  50% extra observation time

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Observation cycle I 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 variable source Galactic Center HEGRA Unidentified TeV2032 Cataclysmic variable (AE Aquari) HESS J1834 MAGIC CRAB pulsar

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Artist’s view of  QSR

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Microquasars 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 T col ~ 2  10 7 M  1/4 Laboratories of jet physics Possible contributors to galactic cosmic rays Compacts jets Radio  IR  X?  gamma? (synchrotron) Disc + corona ? X therm + non therm Large scale ejection Radio & X gamma? Interaction with environment

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Spectral states 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.

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I LS I : 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 AU To observer

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I : radio and x-ray AU To observer Periodic radio outbursts at phases (close to apastron), with intensity and peak position modulated with a 4 yr period X-ray outburst observed ~10 days (  ~ 0.4) before radio outbursts A significant hardening of the x-ray spectrum is observed on the radio onset Photon index X-ray flux Radio flux Greiner & Rau 2001 Paredes et al periastron 33

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I : radio jets 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 The feature on the second day can be associated with the jet of the day before compatible with a velocity of 0.6c The projected angle changes by ~60  in 24 hours

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I :  -rays Hartman et al A HE  -ray (100 MeV – 10 GeV) source detected by EGRET is marginally associated with the position of LS I The emission is variable and peaking at periastron passage (  =0.2) and  ~ Interpreted as stellar photons upscattered (inverse Compton) by relativistic electrons in the jet Tavani et al Massi et al. 2004

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I at Very High Energies MAGIC has observed LS I for 54 hours from November 2005 to March 2006 (6 orbital cycles) A point-like source (E>200GeV) detected with significance of ~9  Position: RA=2 h 40 m 34 s, DEC=61  15’ 25” [  0.4’ (stat),  2’ (syst)] in agreement with LSI position  identification of  -ray source The source is quiet at periastron passage and at relatively high emission level (16% Crab Nebula flux) at later phases [ ] Albert et al. 2006

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Flux time variability Albert et al MAGIC has observed LSI during 6 orbital cycles A variable flux (probability of statistical fluctuation 3  ) detected Marginal detections at phases Maximum flux detected at phase 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!

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources LS I : the film Albert et al 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

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Contemporaneous radio observations 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 Albert et al. 2006

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Energy spectrum Albert et al The average energy spectrum from 200 GeV to 4 TeV is well fitted by a power law with spectral index  = -2.6  0.2 (stat)  0.2 (syst) The luminosity above 200 GeV is ~7 x erg s -1 (assuming a distance of 2 kpc) ~ 6 times that of  QSR LS 5039 (average) It displays more luminosity at TeV energies than at x-rays

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Broad band spectrum Chernyakova et al 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

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Alternative emission models Mirabel 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  -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 B Cons: no pulsed emission; radio jets; M o r e m u l t i - w a v e l e n g t h o b s e r v a t i o n s a r e n e e d e d, m a i n l y V H E + r a d i o Mirabel 2006

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Leptonic vs haroncic In the microquasar scenario, two alternative  -ray production mechanisms are possible: Inverse Compton scattering: e +  → e +  relativistic electrons from the jet with the star of synchrotron photons  Hadron interactions: p + p → X +  0 └→  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  -rays are produced at phase 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. M o r e  - r a y d a t a a n d M u l t i - m e s s e n g e r o b s e r v a t i o n s a r e n e e d e d !

J. Rico (IFAE)Results of MAGIC fist observation cycle on Galactic sources Conclusions The MAGIC IACT has completed its first observation cycle in May % 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 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  -ray production