Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory

Atmospheric parameters, such as pressure (P), temperature (T) and density, affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a ~10% seasonal modulation and ~2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of pressure and density. The former affects the longitudinal development of air showers while the latter influences the Moliere radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory.Comment: 24 pages, 9 figures, accepted for publication in Astroparticle Physic

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{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an active galactic nucleus within 75 Mpc (using the V\'eron-Cetty and V\'eron $12^{\rm th}$ 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 $(38^{+7}_{-6})$, compared with $21$ expected for isotropic cosmic rays. This is down from the early estimate of $(69^{+11}_{-13})$. 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 $2.5\times 10^{17}$ 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% $C.L.$ 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

Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV = 10^18 eV) respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.Comment: 20 pages, 7 figures, 2 tables. Minor changes. Accepted by Astroparticle Physic

Distribución de especies silvestres de papa en el norte del Departamento de La Paz, Bolivia

From 2001 to 2003, field collections of wild potatoes (Solanum Section Petota Solanaceae) were made in the north of the Department of La Paz, Bolivia, with the aim of determining their current distribution in this region. The collection embraced sectors of five provinces: Omasuyos, Larecaja, Camacho, Muñecas and Bautista Saavedra. Five previously described wild species were collected: Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault and S. circaeifolium Bitter, as well as four unidentified species. Some wild potato species in Bolivia, such as S. achacachense, are rare and in danger of extinction because of the destruction of their habitat. In contrast, S. brevicaule, S. candolleanum and S. circaeifolium were recorded in new areas. Some species were affected by pests (Premnotrypes sp.) or the fungus Phytophthora infestans. This is the first time that "Lelekoyas" potatoes (S. tuberosum subsp. andigena) have been detected in the area of influence of Lake Titicaca. In summary, this work reports degrees of genetic erosion for some species, the finding of taxa in new geographical areas, some probable new species, and the presence of P. infestans in some of the species detected.Entre los años 2001 y 2003 se realizaron recolecciones de las principales especies silvestres de papa (Solanum Section Petota Solanaceae) en el norte del Departamento de La Paz, Bolivia, con el objetivo de conocer de su distribución en esta región. La recolección abarcó sectores de cinco provincias: Omasuyos, Larecaja, Camacho, Muñecas y Bautista Saavedra, y se recolectaron cinco especies silvestres ya descritas (Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault y S. circaeifolium Bitter) y cuatro especies no identificadas. Algunas especies silvestres de papa en Bolivia, como S. achacachense, son raras y se encuentran amenazadas de extinción por la destrucción de su hábitat. En cambio, se registraron nuevas zonas con presencia de S. brevicaule, S. candolleanum y S. circaeifolium. Algunas especies se encuentran afectadas por plagas (Premnotrypes sp.) y por patógenos como Phytophthora infestans. Es la primera vez que se registran papas "Lelekoyas" (S. tuberosum subsp. andigena, una especie primitiva) en el área de influencia del Lago Titicaca. Se evidencian grados de erosión genética, distribución en nuevas áreas geográficas, probables nuevas especies y presencia de P. infestans en algunas especies

Distribution of wild potato species in the north of the Department of La Paz, Bolivia

From 2001 to 2003, field collections of wild potatoes (Solanum Section Petota Solanaceae) were made in the north of the Department of La Paz, Bolivia, with the aim of determining their current distribution in this region. The collection embraced sectors of five provinces: Omasuyos, Larecaja, Camacho, Muñecas and Bautista Saavedra. Five previously described wild species were collected: Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault and S. circaeifolium Bitter, as well as four unidentified species. Some wild potato species in Bolivia, such as S. achacachense, are rare and in danger of extinction because of the destruction of their habitat. In contrast, S. brevicaule, S. candolleanum and S. circaeifolium were recorded in new areas. Some species were affected by pests (Premnotrypes sp.) or the fungus Phytophthora infestans. This is the first time that 'Lelekoyas' potatoes (S. tuberosum subsp. andigena) have been detected in the area of influence of Lake Titicaca. In summary, this work reports degrees of genetic erosion for some species, the finding of taxa in new geographical areas, some probable new species, and the presence of P. infestans in some of the species detected.Entre los años 2001 y 2003 se realizaron recolecciones de las principales especies silvestres de papa (Solanum Section Petota Solanaceae) en el norte del Departamento de La Paz, Bolivia, con el objetivo de conocer de su distribución en esta región. La recolección abarcó sectores de cinco provincias: Omasuyos, Larecaja, Camacho, Muñecas y Bautista Saavedra, y se recolectaron cinco especies silvestres ya descritas (Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault y S. circaeifolium Bitter) y cuatro especies no identificadas. Algunas especies silvestres de papa en Bolivia, como S. achacachense, son raras y se encuentran amenazadas de extinción por la destrucción de su hábitat. En cambio, se registraron nuevas zonas con presencia de S. brevicaule, S. candolleanum y S. circaeifolium. Algunas especies se encuentran afectadas por plagas (Premnotrypes sp.) y por patógenos como Phytophthora infestans. Es la primera vez que se registran papas 'Lelekoyas' (S. tuberosum subsp. andigena, una especie primitiva) en el área de influencia del Lago Titicaca. Se evidencian grados de erosión genética, distribución en nuevas áreas geográficas, probables nuevas especies y presencia de P. infestans en algunas especies

Distribution of wild potato species in the north of the Department of La Paz, Bolivia

From 2001 to 2003, field collections of wild potatoes (Solanum Section Petota Solanaceae) were made in the north of the Department of La Paz, Bolivia, with the aim of determining their current distribution in this region. The collection embraced sectors of five provinces: Omasuyos, Larecaja, Camacho, Muñecas and Bautista Saavedra. Five previously described wild species were collected: Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault and S. circaeifolium Bitter, as well as four unidentified species. Some wild potato species in Bolivia, such as S. achacachense, are rare and in danger of extinction because of the destruction of their habitat. In contrast, S. brevicaule, S. candolleanum and S. circaeifolium were recorded in new areas. Some species were affected by pests (Premnotrypes sp.) or the fungus Phytophthora infestans. This is the first time that 'Lelekoyas' potatoes (S. tuberosum subsp. andigena) have been detected in the area of influence of Lake Titicaca. In summary, this work reports degrees of genetic erosion for some species, the finding of taxa in new geographical areas, some probable new species, and the presence of P. infestans in some of the species detected.Entre los años 2001 y 2003 se realizaron recolecciones de las principales especies silvestres de papa (Solanum Section Petota Solanaceae) en el norte del Departamento de La Paz, Bolivia, con el objetivo de conocer de su distribución en esta región. La recolección abarcó sectores de cinco provincias: Omasuyos, Larecaja, Camacho, Muñecas y Bautista Saavedra, y se recolectaron cinco especies silvestres ya descritas (Solanum acaule Bitter, S. achacachense Cárdenas, S. brevicaule (Bitter) Juz and Buk, S. candolleanum Berthault y S. circaeifolium Bitter) y cuatro especies no identificadas. Algunas especies silvestres de papa en Bolivia, como S. achacachense, son raras y se encuentran amenazadas de extinción por la destrucción de su hábitat. En cambio, se registraron nuevas zonas con presencia de S. brevicaule, S. candolleanum y S. circaeifolium. Algunas especies se encuentran afectadas por plagas (Premnotrypes sp.) y por patógenos como Phytophthora infestans. Es la primera vez que se registran papas 'Lelekoyas' (S. tuberosum subsp. andigena, una especie primitiva) en el área de influencia del Lago Titicaca. Se evidencian grados de erosión genética, distribución en nuevas áreas geográficas, probables nuevas especies y presencia de P. infestans en algunas especies

Calibration and Monitoring of the Pierre Auger Observatory

Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009International audienceReports on the atmospheric monitoring, calibration, and other operating systems of the Pierre Auger Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009