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PD Dr. rer. nat. habil. Jochen Greiner

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Automatische Erkennung von nahen kurzen GRBs, um die Suche nach Kilonovae ohne Gravitationswellen-Detektion zu ermoeglichen

The recent detection of gravitational waves (GW) with the advanced LIGO/Virgo instruments in conjunction with a short gamma-ray burst (GRB) and the subsequent discovery of an optical/near-infrared counterpart, the kilonova, has been a spectacular success of multi-messenger astrophysics. The detection of the faint GRB emission far off-axis from the 5-10 deg narrow jet was a big surprise, suggesting that the rate of such events in the local (<100 Mpc) environment is much larger than previously thought.
 
With the special temporal and spectral properties of this GW-GRB as compared to most classical distant short GRBs, such events can also be searched for without GW triggers, as LIGO is upgraded, and thus not operational, until winter 2018. With two previous Bachelor theses  Having developed a physical background model allowing automated fitting, this thesis shall be devoted to establishing a Python program for rapid (<10 min) classification of short GRBs in the local environment.
 
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  (offline 17.12.2017 - 29.1.2018)

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
Themensteller(in): Jochen Greiner
Bestimmung der Masse Schwarzer Loecher in galaktischen Doppelsternsystemen

Some of the most compelling evidence for the existence of black holes in nature comes from the study of so-called X-ray novae,  which are close-binary systems in which matter is transferred  from a late-type companion star onto a compact object. While measuring the orbital periods (and thus a lower limit of the compact object mass) is observationally easy, the determination of the compact star's mass requires the knowledge of the inclination of the orbit. Knowing the mass of the black holes is crucial to determine the spin of black holes. Moreover, the black hole mass distribution is also highly relevant to models of stellar evolution of massive stars, as well as population synthesis models of binary stars due to the intriguing result that the masses of BH transient systems seemingly cluster narrowly around 8 solar masses.
 
The best way to derive the orbital 
inclination is through measuring the color-dependent ellipsoidal  variations along the orbit due to the tidal and rotational distortions  of the Roche-lobe filling secondary as well as its non-uniform suface brightness distribution.  With its capability of simultaneously measuring in seven wavelength channels, GROND provides the means to identify this effect. This thesis is devoted to the analysis and modelling (with the XBinary package) of the existing GROND data of 8 black hole binaries.
 
Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847 (offline 17.12.2017 - 29.1.2018)

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
Themensteller(in): Jochen Greiner
Konzept-Studie fuer einen GRB Cubesat

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-duratino 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 CubeSat (actually a CubeSat swarm). 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 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 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 are helpful. Joy in data analysis is required.

Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847 (offline: 17.12.2017-29.1.2018)

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Test des Shell-Kollisions-Modells mit GROND Daten

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. A current open issue is the origin of the occurence of sudden rebrightenings in the optical signal occasionally detected by MPE's GROND telescope in La Silla, Chile. One explanation for this phenomenon is that they result from late shells of gas ejected by the source and catching up with the forward shock wave.

The thesis shall explore this explanation by comparing the existing results of hydrodynamical simulations to existing GROND data. In particular, a parameter study should be performed in order to cover the range of observational appearance of such collisions. Based on this parameter study, physical parameters like Lorentz factor, total emitted energy and shell thickness should be derived for the sample of observed GRBs.

 The project includes elements from computational, theoretical and observational high-energy astrophysics. No reduction of raw data will be required, but some affinity with computer programming (e.g. c, c++, python) is a must.

 Contact: Jochen Greiner, jcg@mpe.mpg.de, MPE Room 1.3.13, Tel. 30000-3847 (offline 17.12.2017 - 29.1.2018)

geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
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