The multi-messenger group
The focus of our group is the search for point sources of neutrinos with IceCube and the development of a multi-messenger approach, by
combining information on high energy neutrinos and other messengers (e.g. gamma-rays).
For details on our activities please visit our
web site or contact
elisa.bernardini at desy.de
Improvement of the IceCube performance
Algorithms for the reconstruction and selection of events to search of an extraterrestrial
signal from point sources have been
developed over several years by the AMANDA collaboration (e.g. [1,2]).
The IceCube telescope, currenly under construction, will instrument a volume a factor ... bigger.
An extension of the concepts previously used to reconstruct and select events is therefore necessary. In addition, the availability of
a much bigger detector will allow us
the identification of several classes of events, each provinding different information (for example covering a different region in energy).
One of our goals is the extension of the region of sensitivity of the IceCube telescope, both at high and low energies.
We also aim at developing a statistical approach that will allow
us to combine different classes of events.
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Angular regions suitable to the search for cosmic neutrinos. IceCube is optimzed to investigate the TeV region ("up-going events"). At highest energy the earth is not anymore trasparent to neutrinos and searches have to be extended to the horizon.
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Search for time-variable neutrino signals (multi-messenger approach)
The chance to detect cosmic neutrinos from pre-selected objects can be increased by using the
information from established observational windows (multi-messenger approach).
In case of objects showing large time variations in the electromagnetic emission, if correlation is expected between those signals and neutrinos,
data on the electromagnetic emission can be used to select "period of interest".
By limiting the neutrino exposures only on those periods, the signal-to-noise can be largely enhanced and the chance to discover neutrino signals increased [3].
Part of our activities are devoted at collecting and cross-calibrating large amounts of multi-wavelength data (special focus on high energy gamma-rays)
to study the correlations with high energy neutrinos.
A few members of the group work for the MAGIC project, to characterize the behavior of Active galactic Nuclei.
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Example of the multi-messenger approach: the hypotetical flux in gamma-rays is shown for a higly variable object
(bottom).
Whenever the flux in gamma-rays is enhanced (i.e. the source is in a "high state") we can expect that neutrinos are also more likely
to be emitted. By limiting the neutrino observations only on those periods, the integrated background will be lower (top),
improving the signal-to-noise ratio.
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Neutrino triggered Target of Opportunity observations
Due to the limited field-of-view of most telescopes, (quasi-)simultaneous observations at different wavelengths are typically meager.
Target of Opportunity programs (e.g. [5]) address this problem by coordinating measurements at different wavelengths.
The aim of our neutrino triggered Target of Opportunity project is to extend this idea and complement “off-line" time correlation analyses.
Whenever “interesting” neutrino events would be detected from given directions of the sky an alert
can be sent to one ore more telescopes to monitor the corresponding electromagnetic emission.
In some cases the detection of positive coincidences could enhance the discovery chance.
More generally the availability of simultaneous observations is increased. Once the first neutrino signals are established,
this approach may allow constraints on the source modeling. In collaboration with the Max-Planck group in Munich, we realized a first technical implementation of this scheme involving AMANDA and MAGIC, with the aim of a feasibility study (e.g. [6]).
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