Promotionsvortrag Physik: „From the Lab to the Telescopes – Intensity Interferometry with H.E.S.S.“

Ankündigung des Promotionsvortrags von: Herrn Andreas Zmija

Stellar intensity interferometers measure correlations in the flux of photons from the same star (an effect called photon bunching) detected by separated telescopes. By subsequent analysis the an-gular sizes of the stars can be determined. The design of an astronomical intensity interferometer can be simplified to a light collector (telescope) focusing light into a photo-detector. Given that the telescopes do not need high optical quality, arrays of Imaging Atmospheric Cherenkov Telescopes – constructed primarily for the purpose of measuring gamma- and cosmic rays – are ideal candi-dates to operate as stellar intensity interferometers at optical wavelengths.

This talk describes the development of an intensity interferometry application for use at the 12m-diameter telescopes of the High Energy Stereoscopic System (H.E.S.S.) – a gamma-ray telescope array located in Namibia. Initial measurements in the laboratory are presented, where photon bunching was detected and characterized in LED light, measured at low photon rates by time-tagging the arriving photons, as well as in light of a xenon lamp, measured at high photon rates by sampling the photo-current. In a following comparison study, signal-to-noise investigations showed that the photo-current sampling method is perfectly suitable for large telescopes. In 2022, the in-tensity interferometer was installed onto two of the H.E.S.S. telescopes, and measurements of three bright star systems were performed. From these measurements, angular uniform disk di-ameters of the single star σ Sgr as well as of the two primary components in the (effective) binary star system λ Sco – assuming equal stellar diameters – were extracted.

(Vortrag auf Englisch)

Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.