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Optical Astronomy with Cerenkov telescopes

Optical Astronomy with Cerenkov telescopes. E. Oña-Wilhelmi 1,2 , O.C. de Jager 1 , J. Cortina 3 , V. Fonseca 2 1 NWU, Potchefstroom, South Africa. 2 UCM, Madrid, Spain. 3 IFAE, Barcelona, Spain. Erice, July 10 th , 2004. Cerenkov telescopes. Advantages.

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Optical Astronomy with Cerenkov telescopes

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  1. Optical Astronomy with Cerenkov telescopes E. Oña-Wilhelmi1,2, O.C. de Jager1, J. Cortina3, V. Fonseca2 1 NWU, Potchefstroom, South Africa. 2 UCM, Madrid, Spain. 3 IFAE, Barcelona, Spain. Erice, July 10th, 2004

  2. Cerenkov telescopes Advantages • Huge reflectors, i.g. MAGIC has a 230 m2 mirror: ~3 times more light than a 10 m optical telescope. • Very fast light detectors: good for transients. Targets (ms time scale) (1 min-1 hour time scale) Erice, July 10th, 2004

  3. Cerenkov cameras • Digitization of pixel currents (PM). • Single Photo Counting (APD or HPD). Erice, July 10th, 2004

  4. de Oña-Wilhelmi et al., astro-ph/0405088 The Optical Central Pixel Why using an optical central pixel?: Contemporary ephemeris for active pulsars Monitoring of atmospheric conditions Monitoring of transients (high variability of Active Galaxies) Test the telescope data acquisition and analysis software Light of the Night Sky Background What to do in MAGIC?: Test in HEGRA-CT1 to detect the Crab Optical Pulsation HPD testing in progress Erice, July 10th, 2004

  5. 127 pixels each one 0.25° FOV 10 m2 The HEGRA-CT1 Optical Central Pixel • Detection of the Crab optical pulsation: • Cerenkov detectors: • Whipple (10 mreflector) • CELESTE (solar farm) • HEGRA-CT1 (3.5 m diameter reflector) • Future plan: MAGIC Srinivisan et al. 1997 De Naurois et al. 2001 Erice, July 10th, 2004

  6. Pulsed Signal The HEGRA-CT1 Optical Central Pixel 0.25° 0.1° CT1 central pixel LONS+Nebula Erice, July 10th, 2004

  7. The CT1 Central Pixel: PM base and data acquisition R=2 M & C=100 pF -> 0.5 ms • DAQ : PCI NI 6034 E card, 16 analogical inputs, 16 bits resolution • High pass filter to reduce the background Erice, July 10th, 2004

  8. Data analysis • Basic Transformations: Inertial Frame (SSB) • Princeton monthly ephemeris:  and derivates and T0 • i(t) = (To) + (ti-To) + 1/2! d/dt (ti-To)2 • Periodicity search with statistical method (e.g. 2) • 0 (15 Oct)  29.8 Hz Erice, July 10th, 2004

  9. Crab light curve   30.9 Hz  = 0 Nov 8th 2002 Erice, July 10th, 2004

  10. Crab optical signal in 2 hours Nov 8th 2002 (Hz) Erice, July 10th, 2004

  11. Camera point run Application: LONS around Crab Misspointing & PSF -Tauri: Erice, July 10th, 2004

  12. Sensitivity of the method MAGIC for single photon count. method Log(s) MAGIC Single Photon Count.: CT1 5  30s 200s Erice, July 10th, 2004

  13. Conclusions • We detected the Crab Optical Pulsation in 200 s with a 3.5 m diameter telescope. • The detection allowed us to infer the LONS in the galactic anticenter: 2.5 times larger than previous measures done for an extragalactic zone. • Next steps: test the same procedure in MAGIC (DC currents) • use an Hybrid Photo Detector (HPD) Erice, July 10th, 2004

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