1. Jamie Holder School of Physics and Astronomy, University of Leeds, U.K Optical SETI at Leeds Using Cherenkov Light Buckets as Optical SETI Detectors RAS SETI Meeting May 2006

2. What is a ground based gamma-ray telescope? How can they be used for Optical SETI How well do they work? How well could they work? Overview

3. The Whipple 10m gamma-ray telescope 10m 7m Alt-Az mount

4. Incident cosmic ray Particle cascade Cherenkov Light

5. 379 1” PMTs PMT=0.12° PSF~0.14° >2 adjacent PMTs above discriminator threshold to trigger 10ns time coincidence Trigger rate: ~30Hz 2.5° Field of View

6. Simulated Photon Distributions In gamma-ray astronomy, use image shape differences to discriminate gammas from background protons

7. Symmetric: i.e. low ellipticity Ellipticity< 1.5 removes 80% background, keeps 97.5% OSETI flashes OSETI Images are ROUND

8. Optical SETI pulses are bright, with a small radius (R=(width 2 +length 2 )) Cutting below the curve reduces background to ~0. Real Cosmic Ray Images Simulated OSETI Images OSETI Images are COMPACT

9. Image centroid position can be measured to ~+/- 0.02 degree Targeting known star positions reduces background by (2.5/0.04) 2 =4000 Allows to lower minimum pulse size to ~10 photons m -2 HIP 107395 OSETI Images come from a STAR

10. Search Whipple data archive (7 years, 5000 hours) Cross-check with star catalogues Ongoing Work

11. Moonshine? Gamma-Ray Observations are only made when the moon is not visible ~ 800 hours/year of clear sky observations could be used for SETI work: Galactic Plane Survey? 5 minutes on all Northern “HabCat” stars? No investment other than observing and analysis.

12. CANGAROO III H.E.S.S. MAGICVERITAS

13. Increased sensitivity: Stereoscopy

14. Increased sensitivity: Better electronics Integrated Pulse Pulsed laser will have uniform time profile(?)

15. Increased sensitivity: Better optics/tracking PMT size OSETI images will be more compact Reduce allowed region around candidate star Problem – will rarely trigger Need dedicated trigger hardware

16. Optical SETI with Cherenkov light buckets works! Archival data searches ongoing. Follow up observations easy to arrange Dedicated SETI projects are possible with Whipple 10m (especially under moonlight) New arrays will be many times more sensitive, but require trigger hardware Optical SETI should provide some design input to the next generation instruments Many synergies (e.g. Harvard OSETI electronics, ATA mounts) Summary