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

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

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

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

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

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

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 optical + infrared HE (E< 10 GeV) radio, x-ray Periodic variable

Tobias Jogler Max-Planck Institute for Physics Taup 2007 MAGIC Observations LS I was observed for 6 orbits between Oct 05 and March 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

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

Tobias Jogler Max-Planck Institute for Physics Taup 2007 Light Curve of LS I Variable source Highest emission phase 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

Tobias Jogler Max-Planck Institute for Physics Taup 2007 Short Time Variability Search for short time variability on timescales 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~ /12/18 Φ~0.62 Preliminary

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/ /10/27 cycle II 0.6<Φ<0.7 Preliminary

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

Tobias Jogler Max-Planck Institute for Physics Taup 2007 Broad Band Spectrum Chernyakova et al 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)

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 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 within one year Periodicity analysis in progress

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