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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 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
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
Cerenkov cameras • Digitization of pixel currents (PM). • Single Photo Counting (APD or HPD). Erice, July 10th, 2004
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
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
Pulsed Signal The HEGRA-CT1 Optical Central Pixel 0.25° 0.1° CT1 central pixel LONS+Nebula Erice, July 10th, 2004
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
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
Crab light curve 30.9 Hz = 0 Nov 8th 2002 Erice, July 10th, 2004
Crab optical signal in 2 hours Nov 8th 2002 (Hz) Erice, July 10th, 2004
Camera point run Application: LONS around Crab Misspointing & PSF -Tauri: Erice, July 10th, 2004
Sensitivity of the method MAGIC for single photon count. method Log(s) MAGIC Single Photon Count.: CT1 5 30s 200s Erice, July 10th, 2004
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