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PD Dr. rer. nat. habil. Jochen Greiner

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

GEANT-4 Simulation eines Compton Teleskopes

The COMPTEL instrument measured the 0.7-30 MeV emission of the sky for nearly 10 years in the 90ies. This energy range includes interesting nuclear lines from elements which are produced in the winds of massive stars, or in supernova explosions. In addition, the instrument is a perfect polarimeter - and X-/gamma-ray polarimetry is still considered the holy grail of astrophysics. Even now, 20 years later, its data are unique, and no future mission is on the horizon for the next 20 years. However, our computational tools have drastically improved, allowing analysis types which were completely impractical at the time COMPTEL was operated.

This thesis shall take our mass model and perform GEANT4 simulations for two cases: (i) line emission from stellar gamma-ray sources, and (ii) polarized continuums emission. Based on the simulated data, new cuts in the multi-dimentional data space should be found which separate background photons from source photons. Finally, these cuts should be applied to a test data set of COMPTEL in order to evaluate the improvement in the performance.

Technically, this thesis involves learning about (i) data analysis of Compton gamma-ray detectors, (ii) understanding detector effects, (iii) simulating an observation with different levels of statistics, and (iv) characterizing a multi-dimentional parameter space using e.g. principal component analysis.

Some background in astrophysics is advantegeous, and experience with GEANT4 would be perfect. Some Python knowledge is required. Joy in data analysis is required.

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Interpretation von GRB afterglow Spektren mittels Modellspektren aus relativistischen Hydro-Simulationen

Gamma-ray bursts are flashes of gamma-ray resulting from the death of massive stars or the merger of neutron stars. They are followed by an `afterglow' signal that can be be detected from radio to X-rays, produced by a shock wave moving into the gas surrounding the burster at approximately the speed of light. New results from relativistic hydro-dynamical simulations suggest observable differences with respect to the hitherto used analytic description.

    The thesis shall explore these differences for one or more GRBs for which we have the whole set of multi-wavelength data from X-rays to radio. Particular emphasis will be placed on the influence of different priors in the fitting process, and the comparison with analytic results.

    The project includes elements from computational, theoretical and observational high-energy astrophysics. No reduction of raw data will be required, but strong affinity with computer programming (python) and statistical analysis (Bayesian) is a must. On the theoretical side, the project mostly involves (learning about) relativistic hydrodynamics and shock theory. 

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Lokalisierung von Gamma-Ray Bursts mittels Triangulation

Gamma-ray bursts (GRBs) are flashes of gamma-rays resulting from either the death of massive stars (leading to long-duration GRBs) or the merger of two neutron stars (short-duration GRBs). Since the discovery of gravitational waves in conjunction with a short GRB in August 2017, the quest of accurately localizing short GRBs is of utmost importance. Present detector technology has it that detectors with good localization capability detect predominantly long-duration GRBs, while those detectors sensitive to short GRBs have bad localization accuracy.

We have developed a concept for a GRB detection system which should provide accurate localisations for short GRBs, and at the same time is small and simple enough to be flown on a swarm of small satellites. The thesis shall take existing GRB data from the Fermi-GBM satellite, and quantify the sensitivity of the new detector concept. In particular, by using methods for the cross-correlation of unbinned light curves of a given GRB as seen in different detectors the requirements for time resolution and effective area should be derived.

Technically, this thesis involves learning of (i) data analysis of non-imaging gamma-ray detectors, (ii) understanding and correcting detector effects, (iii) simulating light curves with different count statistics, and (iv) analyzing the cross-correlation pattern for binned and unbinned data to derive the dependence of the detector sensitivity on the time resolution and effective area.

Some background in astrophysics is advantegeous. Python knowledge is required, and good programming skills and interest in Bayesian statistics are helpful. Joy in data analysis is required.

    Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Modellierung von physikalischen Prozessen der prompten und Nachleucht-Phase von Gamma-ray bursts

Gamma-ray bursts (GRBs) are flashes of gamma-ray resulting from the death of massive stars or the merger of neutron stars. They are followed by an `afterglow' signal that can be detected from radio to X-rays, produced by a shock wave moving into the gas surrounding the burster at approximately the speed of light. For both phemomena, prompt and afterglow emission, a huge amount of observational data exists. However, modelling is still mostly done with heuristic functions, like power laws, rather than testing against physical models.

We propose three projects aiming at modeling specific mechanisms of the prompt and afterglow phases of GRBs: the emphasis can be put on  (1) modelling of particle escape from GRB blast-waves, (2) theoretical study of correlations between the time evolution of the polarization state and other spectral observables (peak energy, luminosity etc), or (3) numerical computation of synchrotron radiation from an anisotropic electron distribution function and predictions for circular polarization in GRB afterglow.

Technically, this thesis involves learning about (i) physics of GRB prompt (synchrotron) and afterglow emission, (ii) polarization of synchrotron radiation and Compton scattering, (iii) modelling cross-sections of varous processes, and (iv) deriving predictions against which data can be compared with

Some background in astrophysics is advantegeous. Good numerical and or analytical skills are required.

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Suche nach Gamma-Transienten

The recent detection of gravitational waves (GW) with the advanced LIGO/Virgo instruments in conjunction with a short gamma-ray burst (GRB) has surprised gamma-ray astronomers because of the substantially different properties of the GRB signal as compared to canonical GRBs. This motivates an "open-mind" search for untriggered transient events in the data stream of the gamma-ray burst monitor (GBM) on the Fermi satellite. With two previous Bachelor theses we have developed a physical background model, paving the way for automated source and background fitting.

This thesis shall be devoted to establishing a Python program for identifying long-term (> few minutes) transients in Fermi/GBM data, and localizing them on the sky. The project includes elements from computational and observational
high-energy astrophysics, and will allow for obtaining extensive knowledge on the broad class of high-energy transients.

Some background in astrophysics is advantegeous, but affinity with Python programming is a must.

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
Themensteller(in): Jochen Greiner
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