1. 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

2. 2 Cerenkov telescopes 1.Huge reflectors, i.g. MAGIC has a 230 m 2 mirror: ~3 times more light than a 10 m optical telescope. 2.Very fast light detectors: good for transients. Advantages Targets Pulsarmvmv Crab17 PSR B0540-6914 Vela24 PSR B0656+1425 Geminga26 AGNmvmv Mkn 42114.0 Mkn 50114.5 1ES 195912.0 1ES 142616.5 3C27918.0 (ms time scale)(1 min-1 hour time scale)

3. Erice, July 10th, 20043 Cerenkov cameras 1.Digitization of pixel currents (PM). 2.Single Photo Counting (APD or HPD).

4. Erice, July 10th, 20044 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 de Oña-Wilhelmi et al., astro-ph/0405088

5. Erice, July 10th, 20045 The HEGRA-CT1 Optical Central Pixel Detection of the Crab optical pulsation: - Cerenkov detectors: Whipple (10 m reflector) CELESTE (solar farm) -HEGRA-CT1 (3.5 m diameter reflector) - Future plan: MAGIC Srinivisan et al. 1997 De Naurois et al. 2001 10 m 2 127 pixels each one 0.25° FOV

6. Erice, July 10th, 20046 0.1° 0.25° CT1 central pixel The HEGRA-CT1 Optical Central Pixel Pulsed Signal LONS+Nebula

7. Erice, July 10th, 20047 DAQ : PCI NI 6034 E card, 16 analogical inputs, 16 bits resolution High pass filter to reduce the background R=2 M  & C=100 pF -> 0.5 ms The CT1 Central Pixel: PM base and data acquisition

8. Erice, July 10th, 20048 Basic Transformations: Inertial Frame (SSB) Princeton monthly ephemeris: and derivates and T 0  i (t) =  (T o ) + (t i -T o ) + 1/2! d /dt (t i -T o ) 2 Periodicity search with statistical method (e.g.  2) 0 (15 Oct)  29.8 Hz Data analysis

9. Erice, July 10th, 20049  30.9 Hz = 0 Crab light curve Nov 8 th 2002

10. Erice, July 10th, 200410 Nov 8 th 2002 (Hz) Crab optical signal in 2 hours

11. Erice, July 10th, 200411 Application: LONS around Crab Camera point run Misspointing & PSF  -Tauri:

12. Erice, July 10th, 200412 Single Photon Count.: Log(s) CT1 MAGIC MAGIC for single photon count. method 5  200s30s Sensitivity of the method

13. Erice, July 10th, 200413 Conclusions 1.We detected the Crab Optical Pulsation in 200 s with a 3.5 m diameter telescope. 2.The detection allowed us to infer the LONS in the galactic anticenter: 2.5 times larger than previous measures done for an extragalactic zone. 3.Next steps: test the same procedure in MAGIC (DC currents) use an Hybrid Photo Detector (HPD)