PD Dr. rer. nat. habil. Jochen Greiner

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30000-3847
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E-Mail
gu56sil@mytum.de
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Arbeitsgruppe
Max-Planck-Institut für extraterrestrische Physik (MPE)
Funktion
Privatdozent am Physik-Department

Lehrveranstaltungen und Termine

Ausgeschriebene Angebote für Abschlussarbeiten

Genaue Lokalisierungen von Gamma-Ray Bursts mit Fermi/GBM

Recently, we have solved a 25-year old problem of systematic uncertainties in the localization of gamma-ray bursts with scintillation detectors, in particular the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite. The corresponding software is running, and has been tested against 20 GRBs which have arcsec localisations from their X-ray afterglows: this test verifies that the previous systematic untertainty of 8-13 deg has vanished, and bright GRBs can be localized to better than 1 deg.

The present Master thesis shall exploit the science which can be achieved with this dramatic improvement in localization accuracy. First, rapid localizations allow afterglow identifications, and bright Fermi GRBs are expected to be systematically brighter than Swift GRBs, thus offering much more accurate measurements via afterglow spectroscopy. Second, searches for electromagnetic counterparts of gravitational wave triggers of advanced LIGO/Virgo offer a reduction of error boxes from 100 deg radius to 1 deg radius. Third, accurate positions also implies much more accurate spectra of the prompt emission - a systematic analysis is expected to provide stringent constraints on the synchrotron model, the generally accepted standard model of GRB prompt emission.

geeignet als
  • Masterarbeit Kern-, Teilchen- und Astrophysik
Themensteller(in): Jochen Greiner
Inferring the density structure around GRBs
geeignet als
  • Bachelorarbeit Physik
Themensteller(in): Jochen Greiner
Separierung der Emissionsprozesse in Kataklysmischen Veraenderlichen

Cataclysmic variables are binaries consisting of a white dwarf accreting matter from a late-type companion star. The accretion generates copious luminosity, making these systems bright in the optical/X-rays, and depending on the magnetic field strength of the white dwarf, characteristic cyclotron emission is seen in the near-IR. Such actively accreting binaries represent a short phase in the evolution of binary systems. Knowing the accurate space density of such objects would help constrain evolutionary scenarios. Unfortunately, distance estimates are notoriously difficult to measure, since the radiation from the donor needs to be disentangled from the accretion and cycltron components. Correspondingly, the space density is uncertain by about a factor of 2-3 at least.

With our proprietary GROND instrument at the 2.2m MPG telescope in Chile we have been observing a number of such systems. Covering 7 channels simultanously, we are in the position to separate the three emission components: the emission caused by accretion, the cyclotron emission, and the thermal emission from the companion star which in turn allows a distance estimate.

    Technically, this thesis involves learning of (i) astronomical imaging data analysis, (ii) correction of detector effects, (iii) calibration of data, (iv) accurate photometry of point-like objects, (v) decomposing the light into accretion and companion components, and (vi) determining distances based on the spectral properties of the companion.

    Some background in astrophysics is advantegeous. Python knowledge is helpful, and 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
Suche nach ultra-langen 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. Based on the duration of the prompt emission, two classes are known: short GRBs (<2 sec), and long GRBs (2-1000 sec). During the last few years, four GRBs with durations of 2-6 hours (!) have been found. This challenges the standard model of GRB production after the supernova explosion of a massive star, forming a black hole. Thus, it is of utmost interest to find more of such ultralong GRBs. But detections hitherto were only possible with (small) detectors on interplanetary spacecrafts, as those do not suffer the strong variation of background in near-Earth orbits on time-scales of 30 min.

Very recently, in a Master thesis a physical model was developed which successfully describes most of these background variations. This opens the possibility to search the nearly 10-yr data base of the Fermi/GBM detector for unrecognized ultralong GRBs.

Technically, this thesis involves learning of (i) data analysis of non-imaging gamma-ray detectors, (ii) understanding and correcting detector effects, (iii) improving the speed of the present fitting algorithm, and (iv) modelling the data with our background model and identifying transients with durations larger than 1000 sec.

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

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

Kondensierte Materie

Wenn Atome sich zusammen tun, wird es interessant: Grundlagenforschung an Festkörperelementen, Nanostrukturen und neuen Materialien mit überraschenden Eigenschaften treffen auf innovative Anwendungen.

Kern-, Teilchen-, Astrophysik

Ziel der Forschung ist das Verständnis unserer Welt auf subatomarem Niveau, von den Atomkernen im Zentrum der Atome bis hin zu den elementarsten Bausteinen unserer Welt.

Biophysik

Biologische Systeme, vom Protein bis hin zu lebenden Zellen und deren Verbänden, gehorchen physikalischen Prinzipien. Unser Forschungsbereich Biophysik ist deutschlandweit einer der größten Zusammenschlüsse in diesem Bereich.