Time filter

Source Type

Krause J.,Max Planck Institute for Physics | Reichardt I.,Institute Of Fisica Daltes Energies
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

Located in a dense complex environment, W51C provides an excellent scenario to probe accelerated protons in SNRs and their interaction with surrounding target material. Here we report the observation of extended Very High Energy (VHE) gamma-ray emission from the W51C supernova remnant (SNR) with MAGIC. Detections of extended gamma-ray emission in the same region have already been reported by the Fermi and H.E.S.S. collaborations. Fermi/LAT measured the source spectrum in the energy range between 0.2 and 50 GeV, which was found to be well fit by a hadronic neutral-pion decay model. The VHE observations presented here, obtained with the improved MAGIC stereo system, allow us to pinpoint the VHE gamma-ray emission in the dense shocked molecular cloud surrounding the remnant shell. The MAGIC data also allow us to measure, for the first time, the VHE emission spectrum of W51C from the highest Fermi/LAT energies up to several TeV. The spatial distribution and spectral properties of the VHE emission suggest a hadronic origin of the observed gamma rays. Therefore W51C is a prime candidate for a cosmic ray accelerator.


Kovacs A.,Institute Of Fisica Daltes Energies | Garcia-Bellido J.,Autonomous University of Madrid
Monthly Notices of the Royal Astronomical Society | Year: 2016

The alignment of the CMB Cold Spot and the Eridanus supervoid suggests a physical connection between these two relatively rare objects. We use galaxy catalogues with photometric (2MPZ) and spectroscopic (6dF) redshift measurements, supplemented by low-redshift compilations of cosmic voids, in order to improve the 3D mapping of the matter density in the Eridanus constellation. We find evidence for a supervoid with a significant elongation in the line of sight, effectively spanning the total redshift range z < 0.3. Our tomographic imaging reveals important substructure in the Eridanus supervoid, with a potential interpretation of a long, fully connected system of voids. We improve the analysis by extending the line-of-sight measurements into the antipodal direction that interestingly crosses the Northern Local Supervoid at the lowest redshifts. Then it intersects very rich superclusters like Hercules and Corona Borealis, in the region of the Coma and Sloan GreatWalls, as a possible compensation for the large-scale matter deficit of Eridanus. We find that large-scale structure measurements are consistent with a central matter underdensity δ0 ≈ -0.25, projected transverse radius r 0 ⊥ ≈ 195 Mpc h-1 with an extra deepening in the centre, and line-of-sight radius r 0 ∥ ≈ 500 Mpc h-1, i.e. an ellipsoidal supervoid. The expected integrated Sachs-Wolfe imprint of such an elongated supervoid is at the ΔTISW ≈ -40 μK level, thus inappropriate to accounting for the Cold Spot pattern in the CMB. © 2016 The Authors.


Resmini E.,Autonomous University of Barcelona | Santos A.,Autonomous University of Barcelona | Gomez-Anson B.,Hospital Sant Pau | Vives Y.,Institute Of Fisica Daltes Energies | And 6 more authors.
Journal of Clinical Endocrinology and Metabolism | Year: 2012

Context: Cushing's syndrome (CS) affects cognition and memory. Objective: Our objective was to evaluate memory and hippocampal volumes (HV) on 3-tesla magnetic resonance imaging (3T MRI) in CS patients and controls. Patients and Methods: Thirty-three CS patients (11 active, 22 cured) and 34 controls matched for age, sex, and education underwent Rey Auditory Verbal Learning Test and Rey-Osterrieth Complex Figure memory tests. Gray matter and HV were calculated on 3T MRI, using FreeSurfer image analyses software. Results: No differences in HV were observed between active and cured CS or controls. Memory performance was worse in CS patients than controls (P < 0.04 in active; P < 0.03 in cured CS) but did not differ among CS groups, which were therefore analyzed together; they performed worse for verbal (P = 0.02) and visual memory (P = 0.04) than controls. In 12 CS patients, memory was below normative cutoff values for verbal (n = 6, cured), visual memory (n = 10, six cured) or both (n = 4); these patients with severe memory impairments showed smaller HV compared with their matched controls (P = 0.02 with verbal impairment; P = 0.03 with visual impairment). They were older (P = 0.04), had shorter education (P = 0.02), and showed a trend toward longer duration of hypercortisolism (P = 0.07) than the remaining CS patients. Total (P = 0.004) and cortical (P = 0.03) brain gray matter volumes were decreased in CS compared with controls, indicating brain atrophy, whereas subcortical gray matter (which includes HV) was reduced only in the 12 patients with severe memory impairment. Conclusion: Verbal and visual memory is worse in CS patients than controls, even after biochemical cure. HV was decreased only in those whose memory scores were below normative cutoff values. Copyright © 2012 by The Endocrine Society.


Marriner J.,Fermi National Accelerator Laboratory | Bernstein J.P.,Argonne National Laboratory | Kessler R.,University of Chicago | Lampeitl H.,University of Portsmouth | And 7 more authors.
Astrophysical Journal | Year: 2011

We describe a new formalism to fit the parameters α and β that are used in the SALT2 model to determine the standard magnitudes of Type Ia supernovae (SNe Ia). The new formalism describes the intrinsic scatter in SNe Ia by a covariance matrix in place of the single parameter normally used. We have applied this formalism to the Sloan Digital Sky Survey Supernova Survey (SDSS-II) data and conclude that the data are best described by α = 0.135+.033 -.017 and β = 3.19+0.14 - 0.24, where the error is dominated by the uncertainty in the form of the intrinsic scatter matrix. Our result depends on the introduction of a more general form for the intrinsic scatter of the distance moduli of SNe Ia than is conventional, resulting in a larger value of β and a larger uncertainty than the conventional approach. Although this analysis results in a larger value of β and a larger error, the SDSS data differ (at a 98% confidence level) from β = 4.1, the value expected for extinction by the type of dust found in the Milky Way. We have modeled the distribution of SNe Ia in terms of their color and conclude that there is strong evidence that variation in color is a significant contributor to the scatter of SNe Ia around their standard candle magnitude. © 2011. The American Astronomical Society. All rights reserved.


Freitas E.D.C.,University of Coimbra | Monteiro C.M.B.,University of Coimbra | Ball M.,University of Valencia | Gomez-Cadenas J.J.,University of Valencia | And 5 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

The search for neutrinoless double beta decay (0 ν β β) is an important topic in contemporary physics with many active experiments. New projects are planning to use high-pressure xenon gas as both source and detection medium. The secondary scintillation processes available in noble gases permit large amplification with negligible statistical fluctuations, offering the prospect of energy resolution approaching the Fano factor limit. This Letter reports results for xenon secondary scintillation yield, at room temperature, as a function of electric field in the gas scintillation gap for pressures ranging from 2 to 10 bar. A Large Area Avalanche Photodiode (LAAPD) collected the VUV secondary scintillation produced in the gas. X-rays directly absorbed in the LAAPD are used as a reference for determining the number of charge carriers produced by the scintillation pulse and, hence, the number of photons impinging the LAAPD. The number of photons produced per drifting electron and per kilovolt, the so-called scintillation amplification parameter, displays a small increase with pressure, ranging from 141 ± 6 at 2 bar to 170 ± 10 at 8 bar. In our setup, this parameter does not increase above 8 bar due to non-negligible electron attachment. The results are in good agreement with those presented in the literature in the 1 to 3 bar range. The increase of the scintillation amplification parameter with pressure for high gas densities has been also observed in former work at cryogenic temperatures. © 2010 Elsevier B.V. All rights reserved.


Nadal J.,Institute Of Fisica Daltes Energies
Nuovo Cimento della Societa Italiana di Fisica C | Year: 2012

The most precise measurements of top quark pairs (tt̄) production cross-section in proton-proton collisions at a centre-of-mass energy √s = 7 TeV at the LHC are described for the single lepton and fully hadronic decay channels. © CERN on behalf of the ATLAS and CMS Collaborations under CC BY-NC 3.0.


Cortina J.,Institute Of Fisica Daltes Energies | Lopez-Coto R.,Institute Of Fisica Daltes Energies | Moralejo A.,Institute Of Fisica Daltes Energies
Astroparticle Physics | Year: 2016

Current imaging atmospheric Cherenkov telescopes for very high energy γ-ray astrophysics are pointing instruments with a field of view up to a few tens of sq deg. We propose to build an array of two non-steerable (drift) telescopes. Each of the telescopes would have a camera with a FOV of 5 × 60 sq deg oriented along the meridian. About half of the sky drifts through this FOV in a year. We have performed a Monte Carlo simulation to estimate the performance of this instrument. We expect it to survey this half of the sky with an integral flux sensitivity of ∼0.77% of the steady flux of the Crab Nebula in 5 years, an analysis energy threshold of ∼150 GeV and an angular resolution of ∼0.1. For astronomical objects that transit over the telescope for a specific night, we can achieve an integral sensitivity of 12% of the Crab Nebula flux in a night, making it a very powerful tool to trigger further observations of variable sources using steerable IACTs or instruments at other wavelengths. © 2015 Elsevier B.V. All rights reserved.


Cortina J.,Institute Of Fisica Daltes Energies
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

The MAGIC two 17 meter diameter Very High Energy (VHE) γ-ray telescopes have now operated for two years in stereoscopic mode. The performance of the instrument has been evaluated: the integral sensitivity for an energy above 300 GeV is 0.76% Crab units (10% Crab units differential sensitivity below 100 GeV) and the analysis threshold energy is 50 GeV. Highlights of the last two years of observations are the measurement of the Crab Nebula spectrum from ∼50 GeV to ∼50 TeV; the detection of the Crab pulsar up to an energy of 400 GeV, with energy spectra measured for both P1 and P2; the discovery of two new radiogalaxies at VHE (NGC 1275 and IC-310); the absence of an energy cutoff and the discovery of fast variability in the quasars 3C 279 and PKS 1222+21; the discovery at VHE and the characterization of numerous blazars; upper limits to the VHE emission of the Perseus cluster of galaxies and to Dark Matter annihilation in dwarf Spheroidals and the measurement of the electron+positron spectrum between 100 GeV and 3 TeV. MAGIC is currently undergoing a major upgrade of the readout and trigger electronics, and of the camera of the first telescope.


Lopez-Coto R.,Institute Of Fisica Daltes Energies
EPJ Web of Conferences | Year: 2016

The pulsar wind nebula (PWN) 3C 58 is one of the historical very-high-energy (VHE; E>100 GeV) gamma-ray source candidates. It has been compared to the Crab Nebula due to their morphological similarities. This object was detected by Fermi-LAT with a spectrum extending beyond 100 GeV. We analyzed 81 hours of 3C 58 data taken with the MAGIC telescopes and we detected VHE gamma-ray emission for the first time at TeV energies with a significance of 5.7 sigma and an integral flux of 0.65% C.U. above 1 TeV. According to our results 3C 58 is the least luminous PWN ever detected at VHE and the one with the lowest flux at VHE to date. We compare our results with the expectations of time-dependent models in which electrons up-scatter photon fields. The best representation favors a distance to the PWN of 2 kpc and Far Infrared (FIR) comparable to CMB photon fields. Hadronic contribution from the hosting supernova remnant (SNR) requires unrealistic energy budget given the density of the medium, disfavoring cosmic ray acceleration in the SNR as origin of the VHE gamma-ray emission. © The Authors, published by EDP Sciences.


Lopez-Coto R.,Institute Of Fisica Daltes Energies
EPJ Web of Conferences | Year: 2016

The present generation of Imaging Air Cherenkov Telescopes (IACTs) has greatly improved our knowledge on the Very High Energy (VHE) side of our Universe. The MAGIC IACTs operate since 2004 with one telescope and since 2009 as a two telescope stereoscopic system. I will outline a few of our latest and most relevant results: the discovery of pulsed emission from the Crab pulsar at VHE, recently found to extend up to 400 GeV and along the "bridge" of the light curve, the measurement of the Crab nebula spectrum over three decades of energy, the discovery of VHE γ-ray emission from the PWN 3C 58, the very rapid emission of IC 310, in addition to dark matter studies. The results that will be described here and the planned deep observations in the next years will pave the path for the future generation of IACTs. © The Authors, published by EDP Sciences.

Loading Institute Of Fisica Daltes Energies collaborators
Loading Institute Of Fisica Daltes Energies collaborators