Homage for Alexander Konopelko

On August 10, Dr. Alexander Konopelko, a long-time scientific associate of our institute and a member of the HEGRA and H.E.S.S. Collaborations, died in a car accident near Pittsburg, Kansas (U.S.A.). He was an Assistant Professor at Pittsburg State University.

Alexander Konopelko, whom we called Sascha – as his Russian friends did – was a student of Professor Alexander Plyasheshnikov at the Physics Department of Altai University in Barnaul (Russia). In his PhD thesis he extended Plyasheshnikov’s simulations of atmospheric Air Showers, induced by energetic particles incident on the Earth from space, and applied them especially in the direction of their Cherenkov light emission. This numerical code by Plyasheshnikov and Konopelko is called the “Altai code”. Sascha came originally in the 1990s as a regular guest to the institute and later worked here as research associate. Then he joined the Humboldt University group of H.E.S.S. in Berlin. In 2004 he moved to the US, first to Purdue University and then to Pittsburg State University.

Konopelko made important contributions to the problem of the discrimination of the charged particle background for imaging atmospheric Cherenkov telescopes and the energy estimation of very high energy gamma rays, among related activities. Together with others he also applied these results to systems of telescopes. His simulations for the HEGRA project ( = High Energy Gamma-Ray Astronomy) on La Palma constituted the basis for the transposition of the telescope measurements to telescope energy thresholds, actual photon energies, fluxes and energy spectra. For the analysis of observations of expected gamma-ray sources like the Crab Nebula he derived the data cuts not from the data themselves or from neural net analyses, but rather from the direct Monte Carlo simulations of the cosmic ray background which he compared with the measured background distributions. The fact that theses comparisons showed such a close correspondence lent a special credibility to the data analysis. He was also an active observer on La Palma.

Subsequently he was instrumental in studies for the Cherenkov project H.E.S.S. ( = High Energy Stereoscopic System) in Namibia where MPIK is a major part of a, by now, large European collaboration. Almost all the early Monte Carlo estimates concerning the instrument threshold, flux sensitivities, point spread function and energy resolution are due to him. The corresponding two publications in Vol. 6 of the journal Astroparticle Physics: “The Potential of Ground-Based Arrays of Imaging Atmospheric Cherenkov Telescopes I, II”, in 1997, by Aharonian, Hofmann, Konopelko, and Völk, were the basis for the concept of this array.

Alex Konopelko has been extremely active in Heidelberg. He was one of the key members of the Astrophysics Division and we all liked him as a colleague. Besides his instrumental work he became interested in questions of high energy astrophysics pursued with these instruments. Among other efforts he has been involved in interpretative efforts regarding the gamma-ray emission from the Blazar Mrk 501, and his interest concerned supernova remnants as potential cosmic-ray sources, as well as Pulsars und Pulsar Wind Nebulae.

Alex Konopelko was a very likeable person. He was not outgoing, sometimes even shy. But he had a good sense of humour which made life with him pleasant and enjoyable. Last year he visited the institute with a group of students from Pittsburg State University. They heard science presentations by institute members and we enjoyed their youthful interest.
Alex Konopelko is leaving behind his wife and his two daughters. We shall keep his memory in honour and sympathy.