Research

Astroparticle Physics

For more than six years, I am working in the field of astroparticle physics, more specifically in the area of high-energy-astrophysics and gamma-ray astronomy. My main scientific interest is focused on active galactic nuclei (AGN).
The work for my Diploma thesis, conducted under the supervision of Prof. Dr. Karl Mannheim at the University of Würzburg, relied on data from the MAGIC telescopes (La Palma, Canary islands) and was focused on the gamma-ray variability time scales of IC 310, an AGN with a remarkable, radio-emitting jet and further exciting properties. This object had been classified as a so-called head-tail radio galaxy for more than 40 years. The findings from the MAGIC observation with regards to the flux variability indicated a different nature of the object. Indeed, first VLBI radio observations conducted by my collaborators and myself afterwards showed a blazar-like radio jet structure (see Kadler, Eisenacher et al. 2012).
After obtaining the Diploma degree, I continued working on fast variability of active galactic nuclei in the same research group, but expanded my research by additional broadband multiwavelength emission data from different sources. Among other things, I led and conducted the first multiwavelength campaign on IC 310 including radio, optical, UV, X-ray, and gamma-ray instruments. Furthermore, I am very actively working on MAGIC data analysis using ROOT (C/C++, analysis and statistic software package from CERN) and looking for new approaches in this respect.
The scientific findings from my research have been published in several articles, conference proceedings, and peer-reviewed journals. Among the latter, I would like to draw your attention to the article, in which we identify acceleration processes close to the black hole of IC 310 based on a combination of ultra-rapid variability inferred from MAGIC data and high-resolution very-long baseline observations with EVN. The corresponding results give clues on key questions of AGN and high-energy astronomy such as how jets in AGN could be created, acceleration processes of cosmic rays, production of gamma-rays, and physics of shocks. Thanks to these investigations and my current work, I obtain deep insight into theoretical models for variability in light curves of AGN with shock-acceleration, relativistic reconnection, star/jet interactions, and magnetospheric models (see figure above), as well as the modeling of broad-band spectral energy distributions.
In addition, I have contributed in the study of AGN in the Southern Hemisphere within TANAMI program. Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) is a multiwavelength program for monitoring extragalactic jets of AGN on the Southern Hemisphere. Also, in cooperation with the ANTARES Collaboration, we have conducted multi-messenger studies of AGN located spatially close to the PeV neutrinos detected by IceCube (see Krauß et al., A&A, 2014, Adrián-Martínez et al. 2015, arXiv: 1501.07843, and Kadler et al. 2016, Nature Physics, arXiv: 1602.02012).

Observations

Until 2016, I was a member of the MAGIC Collaboration. MAGIC (Major Atmospheric Gamma Imaging Cherenkov) is a system of two 17 m diameter Imaging Atmospheric Cherenkov Telescopes (IACT) located on the Canary Island of La Palma, Spain. Since 2017, I working with H.E.S.S. (High Energy Stereoscopic System). The IACT technique enables us to perform measurement of gamma rays in the energy range of the electromagnetic spectrum between 30 GeV and 50 TeV. Besides my usual observational shifts, I participated in the commissioning of the MAGIC telescopes after a major upgrade for two one-month periods in 2011 and 2012.
In addition to the aforementioned work, there are several occasions at which I have the chance to work with colleagues from the radio, optical, X-ray, MeV-GeV (Fermi-LAT) communities. I already have successfully submitted several proposals as principal investigator to other telescopes. Prominent examples are the European VLBI Network (EVN), the Effelsberg 100m telescope, INTEGRAL, Swift, and XMM-Newton.