1. Tobias Jogler Max-Planck Institute for Physics Taup 2007 MAGIC Observations of the HMXB LS I +61 303 in VHE gamma rays Tobias Jogler on behalf of the MAGIC Collaboration TAUP ’07

2. Tobias Jogler Max-Planck Institute for Physics Taup 2007 The MAGIC Telescope La Palma, asl. 2200m 17 m diameter mirror 3.5 ° FoV camera Trigger threshold of E = 60 GeV Sensitivity of 2.2 % Crab flux Can operate under moonlight conditions Very sensitive instrument to study faint VHE gamma ray sources

3. Tobias Jogler Max-Planck Institute for Physics Taup 2007 MAGIC II 2nd MAGIC telescope under constructionIn stereo observation mode with both telescopes we will have a 3 times better sensitivity than MAGIC I MAGIC II 7-5 cleaning

4. Tobias Jogler Max-Planck Institute for Physics Taup 2007 LS I +61 303 a HMXB HMXB: Binary systems with massive star and lighter compact object orbiting the massive star LS I +61 303 B0 V star with disc (Be) Compact object unknown Orbital period 26.496 days Distance ~ 2 kpc Periastron at  = 0.23 Eccentricity e = 0.73

5. Tobias Jogler Max-Planck Institute for Physics Taup 2007 LS I - a Microquasar ? Production of γ - rays: e + γ LE e + γ VHE γ LE from synchrotron radiation or γ LE from companion star p + Ion π 0 + π ± γ γγ γ Features: - accretion disc - jets - modulation with accretion rate Mirabel 2006

6. Tobias Jogler Max-Planck Institute for Physics Taup 2007 LS I a Binary Pulsar ? Production of γ - rays: e + γ LE e + γ VHE γ LE from companion star e from relativistic PW Features: - no accretion disc - no jet Mirabel 2006 p + Ion π 0 + π ± γ γγ γ

7. Tobias Jogler Max-Planck Institute for Physics Taup 2007 LS I Observation Detected in radio, optical, x-ray, possibly at HE (E< 10 GeV) gamma rays Paredes et al. 1997Tavani et al. 1998Mendelson et al. 1989 optical + infrared HE (E< 10 GeV) radio, x-ray Periodic variable

8. Tobias Jogler Max-Planck Institute for Physics Taup 2007 MAGIC Observations LS I was observed for 6 orbits between Oct 05 and March 06 54 hours of data, 22% of data taken during moon 2nd observation campaign in Sep to Dec 2006, 112 hours of data In total ~ 166 hours of data !!! Clear detection in 1st campaign with 8.7 sigma Excess position: RA=2h 40m 34s DEC= + 61  15’ 25” In agreement with LS I position

9. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Light Curve of LS I +61 303 Variable source Highest emission ~ phase 0.6 Quiet at periastron Periastron Oct 2005 Nov 2005 Dec 2005 Jan 2006 Feb 2005 Mar 2005

10. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Light Curve of LS I +61 303 Variable source Highest emission phase 0.6-0.7 Quiet at periastron Second peak in Dec 06 at 0.85 Oct 2006 Nov 2006 Sep 2006 Dec 2006 Preliminary Dec 2006 Swift, Esposito et al 2007

11. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Short Time Variability Search for short time variability on timescales 30 - 75 min No short time variability found within the sensitivity of MAGIC Searched in all nights, as examples the two longest nights with t > 4h Preliminary 2006/11/18 Φ~0.47 2006/12/18 Φ~0.62 Preliminary

12. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Spectral Behavior Spectral behavior is stable even if flux changes by factor of 3 Well fitted by power- law with spectral index 2.6  0.2 stat  0.2 sys 2006/12/18 2006/10/27 cycle II 0.6<Φ<0.7 Preliminary

13. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Gamma-ray / X-ray Correlation Swift observed LS I from Sep to Dec 2006 with XRT instrument using 24 pointings Swift Correlation r = 0.99 But not strictly simultaneous and Swift saw short time variability Interesting but should not be over-interpreted P.Esposito et al 2007 MAGIC

14. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Broad Band Spectrum Chernyakova et al. 2006 additional VHE γ - ray production due to hadronic mechanism? Multiwavelength campaigns are very important to understand LS I IC model for the Binary Pulsar scenario (data not simultaneous)

15. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Conclusion Detection of a variable galactic source in VHE γ – rays (recently confirmed by Veritas collaboration) Highest emission not at periastron but around phase 0.6-0.7 Spectral break between 10 and 200 GeV Acceleration mechanism still unknown No variability seen on timescales of 30 min to 75 min Stable spectral index in phase bins 0.5-0.7 within one year Periodicity analysis in progress

16. Tobias Jogler Max-Planck Institute for Physics Taup 2007 Thank You