| abstract |  To date, no neutrinos with energies in or above the GeV range have been identified from astrophysical objects. The aim of the two analyses described in this dissertation is to observe high-energy muon neutrinos from Gamma Ray Bursts (GRBs). GRBs are distant sources, which were discovered by satellites recording their flashes of high-energy electromagnetic radiation. In some cases, the gamma-ray flashes are followed by lower energy radiation. GRBs are observed to have a well localized position and a short duration. This allows us to reduce the background in searching the data of the AMANDA/IceCube detector for a possible signal. As no detection of those highly energetic neutrinos has succeeded so far, we aim to analyze our data in a rather unbiased way and limit the
dependence on theoretical modelling of the GRB engine. To this end we filter the
data using parameters which depend only weakly on the neutrino energy spectrum
(unlike a previous analysis in Achterberg et al. (2007)). Besides this, we allow for a
possible time di erence between the arrival time of the prompt photon emission and
the neutrino signal: our analyses are sensitive to signals arriving within one hour
of the satellite trigger time (whereas previous analyses followed an approach which
is only sensitive for signals within ten minutes centered around the arrival of the
prompt -s (Achterberg et al. 2008)).
The two separate analyses presented here di er in one important aspect: in the
analysis of the specific burst GRB080319B we analyze the data of one single GRB
event for the presence of neutrinos from this GRB. The central assumption is that this
”brightest GRB observed to date” might produce a high-energy neutrino flux which
is significantly higher than the average GRB neutrino flux. (This approach was also
followed in the analysis of the data of GRB030329 (Stamatikos & et al. 2005).) The
second analysis we present is based on stacking the data of multiple GRBs (with
average properties) to cope with low fluxes. The directional and timing information
of the GRBs used in our analyses is taken from these sources. As we do not use
complex spectral information and the required resolution on time and location is
moderate, we can incorporate the information of various experiments. Most of the
GRBs in our sample were observed by the Swift satellite, others by Fermi, Integral,
SuperAgile or IPN (the InterPlanetary Network).
In chapter 2 we briefly outline the leading GRB models and discuss to what extent
our analyses depend on model assumptions. In chapter 3 we give the characteristics
of our detector. Subsequently in chapter 4 we provide all details on how we calibrate
the detector and process the data. The method we will use to assess the significance
of our observations is outlined in chapter 5. The details of the analyses themselves
are given in chapters 6 and 7. We discuss the results in chapter 8. |
Order a printed copy