19 research outputs found
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
An upper limit to the photon fraction in cosmic rays above 1019 eV from the Pierre Auger Observatory
An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 1019 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample support the conclusion that a photon origin of the observed events is not favored. © 2006 Elsevier B.V. All rights reserved
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for anisotropies near the direction of the Galactic Centre at EeV energies. The exposure of the surface array in this part of the sky is already significantly larger than that of the fore-runner experiments. Our results do not support previous findings of localized excesses in the AGASA and SUGAR data. We set an upper bound on a point-like flux of cosmic rays arriving from the Galactic Centre which excludes several scenarios predicting sources of EeV neutrons from Sagittarius A. Also the events detected simultaneously by the surface and fluorescence detectors (the 'hybrid' data set), which have better pointing accuracy but are less numerous than those of the surface array alone, do not show any significant localized excess from this direction. © 2006 Elsevier B.V. All rights reserved
Properties and performance of the prototype instrument for the Pierre Auger Observatory
Copyright © 2003 Elsevier B.V. All rights reserved.Construction of the first stage of the Pierre Auger Observatory has begun. The aim of the Observatory is to collect unprecedented information about cosmic rays above 1018 eV. The first phase of the project, the construction and operation of a prototype system, known as the engineering array, has now been completed. It has allowed all of the sub-systems that will be used in the full instrument to be tested under field conditions. In this paper, the properties and performance of these sub-systems are described and their success illustrated with descriptions of some of the events recorded thus far.Auger Collaboration, ..., J. A. Bellido, ..., R. W. Clay, ..., B. R. Dawson, ..., G. J. Thornton, ..., N. R. Wild, et al.http://www.elsevier.com/wps/find/journaldescription.cws_home/505701/description#descriptio
Upper Limit on the Cosmic-ray Photon Flux Above 10**19-eV Using the Surface Detector of the Pierre Auger Observatory.
A method is developed to search for air showers initiated by photons using
data recorded by the surface detector of the Auger Observatory. The approach is
based on observables sensitive to the longitudinal shower development, the
signal risetime and the curvature of the shower front. Applying this method to
the data, upper limits on the flux of photons of 3.8*10^-3, 2.5*10^-3, and
2.2*10^-3 km^-2 sr^-1 yr^-1 above 10^19 eV, 2*10^19 eV, and 4*10^19 eV are
derived, with corresponding limits on the fraction of photons being 2.0%, 5.1%,
and 31% (all limits at 95% c.l.). These photon limits disfavor certain exotic
models of sources of cosmic rays. The results also show that the approach
adopted by the Auger Observatory to calibrate the shower energy is not strongly
biased by a contamination from photons.Comment: 28 pages, 9 figures; v2: minor modifications; accepted by Astropart.
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