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VHE g -ray observations of the AGN 1ES1959+650 with the HEGRA CT1 Cherenkov Telescope

VHE g -ray observations of the AGN 1ES1959+650 with the HEGRA CT1 Cherenkov Telescope. Overview. 1ES1959+650 CT1 Data, obs.time ALPHA distr. Light Curve Spectrum Summary. Nadia Tonello Max Planck Institute for Physics (Werner-Heisenberg-Institut), Munich, Germany

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VHE g -ray observations of the AGN 1ES1959+650 with the HEGRA CT1 Cherenkov Telescope

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  1. VHE g-ray observations of theAGN 1ES1959+650with the HEGRA CT1Cherenkov Telescope Overview • 1ES1959+650 • CT1 • Data, obs.time • ALPHA distr. • Light Curve • Spectrum • Summary Nadia Tonello Max Planck Institute for Physics (Werner-Heisenberg-Institut), Munich, Germany for the HEGRA Collaboration 28th ICRC, Tsukuba

  2. HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary The AGN 1ES1959 +650 1993: identified from the radio, optical and X-ray emissions (Einstein IPC Slew Survey) . 1998: First g-ray emission Seven Telescope Array in Utah (Nishiyama et al., 26th ICRC, OG.2.1) 2000: observations by the HEGRA Cherenkov Telescopes 2002: Short flare seen by the VERITAS collaboration (Dowdall et al., IAU Circ. 7903) Elliptical galaxy Active Galactic Nucleus BL Lac object z = 0.047 RA =19h59m59.8s Dec = +65d08'54'' Nadia Tonello MPI for Physics, Munich 1 28th ICRC, Tsukuba

  3. HEGRA CT1 Cherenkov Telescope for g-ray detection HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary 28.75°N 17.89°W 2200 asl ORM, La Palma, . Canary Islands Reflecting surface 10.3 m2 area aluminum mirrors Camera 127 pixels FOV 3° diam. Energy threshold 750 GeV at small ZA Sensitivity 3.3 s x for a Crab-like source Nadia Tonello MPI for Physics, Munich 2 28th ICRC, Tsukuba

  4. HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary Data and observation time 2000 2001 2002 Good dark nights, nom hv 58 h 86 h 174.2 h Weak moonlight no hv red.24 h 8.1 h Moonlight 4%hv reduction 12 h 16.1 h Moonlight 8%hv reduction8 h 6.1 h Moonlight 12%hv reduction7 h 2.9 h Dynamical cuts applied on the image parameter distributions of the showers: ZA, SIZE and DIST dependent Nadia Tonello MPI for Physics, Munich 3 28th ICRC, Tsukuba

  5. ALPHA distribution HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary MJD: 52412 - 52584 ZA range: 36.4°- 54.2° obs.time: 174.2 h nom data Cut in ALPHA= 13.1 deg Significance: 11.1 s Excess: 691 ± 42 off: 1826 ± 38 Comparison of the fit result with a normalized sample of off-data Nadia Tonello MPI for Physics, Munich 4 28th ICRC, Tsukuba

  6. Light curve HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary Nov. May Aug. June July Sept. Periods of high activity: 20 May (MJD52414) 2 June(MJD52427) 14-15 July (MJD52469-70) Nadia Tonello MPI for Physics, Munich 5 28th ICRC, Tsukuba

  7. Correlation study HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary HEGRA CT1 En.range 1 -10 TeV All-Sky-mon. En.range 2 -12 keV Nadia Tonello MPI for Physics, Munich 6 28th ICRC, Tsukuba

  8. Energy spectrum HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary MJD: 52412 - 52584 ZA range: 36.4°- 54.2° obs.time: 174.2 h nom data Fit: pure power law(dashed line) dF/dE = f0 (E/TeV) -a c2/d.o.f. = 9.9 / 5 f0 = (0.78± 0.13) 10 -11 cm -2 s-1 TeV-1 a = 3.52 ± 0.18 Fit: power law function and exponential cut-off (solid line) dF/dE = f0 (E/TeV) -a e -(E/E0) c2/d.o.f. = 6.3 / 5 f0 = (1.17± 0.27) 10 -11 cm -2 s-1 TeV-1 a = 2.3 (fixed) E0 = (1.79 ± 0.31) TeV Nadia Tonello MPI for Physics, Munich 7 28th ICRC, Tsukuba

  9. Summary and Conclusions HEGRA CT1 observations of 1ES1959+650 1ES1959+650 CT1 Data, obs.time ALPHA distrib. Light curve En. Spectrum Summary We observed 1ES1959+650 in 2000, 2001 and 2002. Low flux recorded in 2000, 2001 (no significant signal in CT1). In 2002, three periods of increased flux have been seen, one of them recorded during moonlight conditions. No clear correlation between flares in the X-ray and g-ray regions. Study in progress. Spectrum compatible with a power law, well described also adding a cut-off. Due to lack of statistics, no decisive discrimination possible. Nadia Tonello MPI for Physics, Munich 8 28th ICRC, Tsukuba

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