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

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 a3 times better sensitivity than MAGIC I

MAGIC II7-5 cleaning

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

Tobias Jogler Max-Planck Institute for Physics Taup 2007

LS I - a Microquasar ?

Production of γ - rays:

e + γ LE e + γVHE

γLE from synchrotron radiation

or γLE from companion star

p + Ion π0 + π±

γ 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 + γLE e + γVHE

γLE from companion star

e from relativistic PW

Features: - no accretion disc

- no jet

Mirabel 2006

p + Ion π0 + π±

γ 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. 1997 Tavani et al. 1998 Mendelson et al. 1989

optical + infraredHE (E< 10 GeV) radio, x-ray

Periodic

Periodic Periodic

Periodicvariable

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= + 6115’ 25”

In agreement with LS I position

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

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

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 > 4hPreliminary

2006/11/18 Φ~0.47

2006/12/18 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

2006/12/18

2006/10/27

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

SwiftCorrelation 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. 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)

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

Tobias Jogler Max-Planck Institute for Physics Taup 2007

Thank You