1,446 research outputs found
A Systematic Study on Energy Dependence of Quasi-Periodic Oscillation Frequency in GRS 1915+105
Systematically studying all the RXTE/PCA observations for GRS 1915+105 before
November 2010, we have discovered three additional patterns in the relation
between Quasi-Periodic Oscillation (QPO) frequency and photon energy, extending
earlier outcomes reported by Qu et al. (2010). We have confirmed that as QPO
frequency increases, the relation evolves from the negative correlation to
positive one. The newly discovered patterns provide new constraints on the QPO
models
BRIVA-LIFEâA multicenter retrospective study of the long-term use of brivaracetam in clinical practice
Objectives: Evaluate long-term effectiveness and tolerability of brivaracetam in clinical practice in patients with focal epilepsy.
Materials and Methods: This was a multicenter retrospective study. Patients aged =16Â years were started on brivaracetam from November 2016 to June 2017 and followed over 1Â year. Data were obtained from medical records at 3, 6 and 12Â months after treatment initiation for evaluation of safety- and seizure-related outcomes.
Results: A total of 575 patients were included in analyses; most had been treated with =4 lifetime antiepileptic drugs. Target dosage was achieved by 30.6% of patients on the first day. Analysis of primary variables at 12 months revealed that mean reduction in seizure frequency was 36.0%, 39.7% of patients were =50% responders and 17.5% were seizure-free. Seizure-freedom was achieved by 37.5% of patients aged =65 years. Incidence of adverse events (AEs) and psychiatric AEs (PAEs) was 39.8% and 14.3%, respectively, and discontinuation due to these was 8.9% and 3.7%, respectively. Somnolence, irritability, and dizziness were the most frequently reported AEs. At baseline, 228 (39.7%) patients were being treated with levetiracetam; most switched to brivaracetam (dose ratio 1:10-15). Among those who switched because of PAEs (n = 53), 9 (17%) reported PAEs on brivaracetam, and 3 (5.7%) discontinued because of PAEs. Tolerability was not highly affected among patients with learning disability or psychiatric comorbidity.
Conclusions: In a large population of patients with predominantly drug-resistant epilepsy, brivaracetam was effective and well-tolerated; no unexpected AEs occurred over 1Â year, and the incidence of PAEs was lower compared with levetiracetam
A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni
Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kiloÂâelectron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems.
This article has a correction. Please see: http://science.sciencemag.org/content/360/6386/eaat927
The exposure of the hybrid detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays.
It consists of a surface array to measure secondary particles at ground level
and a fluorescence detector to measure the development of air showers in the
atmosphere above the array. The "hybrid" detection mode combines the
information from the two subsystems. We describe the determination of the
hybrid exposure for events observed by the fluorescence telescopes in
coincidence with at least one water-Cherenkov detector of the surface array. A
detailed knowledge of the time dependence of the detection operations is
crucial for an accurate evaluation of the exposure. We discuss the relevance of
monitoring data collected during operations, such as the status of the
fluorescence detector, background light and atmospheric conditions, that are
used in both simulation and reconstruction.Comment: Paper accepted by 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{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
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
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
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