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 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 B Vela24 PSR B Geminga26 AGNmvmv Mkn Mkn ES ES C (ms time scale)(1 min-1 hour time scale)

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

Erice, July 10th, 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/

Erice, July 10th, 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 De Naurois et al m pixels each one 0.25° FOV

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

Erice, July 10th, 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

Erice, July 10th, 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

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

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

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

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

Erice, July 10th, 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)