52 research outputs found
Constraints on the properties of the turbulent magnetic field around Geminga using HAWC measurements
We place constraints on the properties of the interstellar turbulence that
surrounds Geminga pulsar, using the recent measurements from the HAWC
Observatory in this region. We propagate very-high-energy electrons in
realizations of 3D isotropic Kolmogorov or Kraichnan turbulence, calculate
their gamma-ray emission, and compare with HAWC measurements. We show that the
measurements can be well fitted for both models of the turbulence and for
reasonable values of its strength, , and coherence length, . Our best fits are obtained for G and pc. Furthermore, the absence of strong asymmetries in the observed
emission favours pc.Comment: 6 pages, 3 figures. Submitted to Journal of Physics: Conference
Series. Talk presented at the 26th Extended European Cosmic Ray Symposium,
Barnaul, July 201
Constraining the properties of the magnetic turbulence in the Geminga region using HAWC -ray data
Observations of extended gamma-ray emission around Galactic cosmic-ray (CR)
sources can be used as novel probes of interstellar magnetic fields. Using
very-high-energy gamma-ray data from the HAWC Observatory, we place constraints
on the properties of the magnetic turbulence within pc from
Geminga. We inject and propagate individual CR electrons in 3D realizations of
turbulent magnetic fields, calculate the resulting gamma-ray emission, and
compare with HAWC measurements of this region. We find that HAWC data is
compatible with expectations for Kolmogorov or Kraichnan turbulence, and can be
well fitted for reasonable coherence lengths and strengths of the turbulence,
despite implying a CR diffusion coefficient significantly smaller than those
suggested by Galactic CR propagation codes. The best fit is found for a
coherence length pc and a magnetic field strength G, and the preferred value for increases with
. Moreover, the apparent lack of strong asymmetries in the
observed emission allows us to constrain the coherence length to pc in this region.Comment: submitted to MNRA
Baseline Design for a Next Generation Wide-Field-of-View Very-High-Energy Gamma-Ray Observatory
The TeV gamma ray sky is observable by recording footprints of extensive air
showers with an array of particle detectors. In the northern hemisphere there
are currently two projects employing this technique: The HAWC gamma ray
observatory which is currently operational in Mexico and LHAASO in the Sichuan
region in China which is currently under development. In the southern
hemisphere several efforts are currently ongoing to investigate the feasibility
of a similar observatory at very high altitude sites in the Andes. The science
case for such an observatory should be complementary to the science to be
performed by the future Cherenkov Telescope Array. There are two clear
directions in which such an observatory could optimize its performance.
Firstly, optimize the performance of sub-TeV energies. This is especially
important to provide an unbiased monitoring of a large fraction of the sky for
observations of transient and extended sources. Secondly, to obtain the largest
photon statistics above roughly 50 TeV, which requires a large collection area
with sufficient performance in angular and energy resolution. This would enable
to extend spectral measurements of Galactic sources and gives the opportunity
to search for dark matter and exotic physics in a new energy range. Using
simulated air showers and a generalized detector description the performance of
a conceptual observatory is studied and the ways to optimize it will be
discussed. With this approach the baseline design of such an observatory can be
obtained without the need of detailed simulations of the detector hardware.Comment: Proceeding if the 35th International Cosmic Ray Conferenc
Characteristics of extensive air showers around the energy threshold for ground-particle-based gamma-ray observatories
Very high energy gamma-ray astronomy based on the measurement of air shower
particles at ground-level has only recently been established as a viable
approach, complementing the well established air Cherenkov technique. This
approach requires high (mountain) altitudes and very high surface coverage
particle detectors. While in general the properties of air showers are well
established for many decades, the extreme situation of ground-level detection
of very small showers from low energy primaries has not yet been well
characterised for the purposes of gamma-ray astronomy. Here we attempt such a
characterisation, with the aim of supporting the optimisation of
next-generation gamma-ray observatories based on this technique. We address all
of the key ground level observables and provide parameterisations for use in
detector optimisation for shower energies around 1 TeV. We emphasise two
primary aspects: the need for large area detectors to effectively measure
low-energy showers, and the importance of muon identification for the purpose
of background rejection.Comment: This is a pre-print of an article published in EPJC. The final
authenticated version is available online at:
https://doi.org/10.1140/epjc/s10052-019-6942-
Constraining the Diffusion Coefficient with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae
Nearby electron/positron accelerators, mostly Pulsar Wind Nebulae (PWNe),
have been proposed as potential origins of the positron excess above 10 GeV.
The HAWC Observatory reveals two very extended sources spatially coincident
with two nearby middle-aged pulsars: Geminga and PSR B0656+14, suggesting
ultrarelativistic electrons/positrons accelerated in our backyard.
Morphological studies on these two PWNe provide a constraint on the diffusion
coefficient at HAWC energies. In this poster, we will present the model
development and morphological studies on these PWNe, and the derived diffusion
coefficient that best fits the data.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017),
Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution
High energy gamma-ray emission powered by a young protostar: the case of S255 NIRS 3
Evidence of efficient acceleration of cosmic rays in massive young stellar
objects has been recently reported. Among these massive protostars, S255 NIRS 3
for which extreme flaring events associated with radio jets have been detected,
is one of the best objects to test this hypothesis. We search for gamma-ray
emission associated with this object in Fermi-LAT data and inspect the gas
content in different molecular lines using the MWISP survey. A GeV source
dubbed 4FGL J0613.1+1749c lies on top of the MYSO region, where two filamentary
~10 pc CO structures extend along the same direction of the sub-parsec radio
jets. We investigate the spectrum, morphology, and light curve of the gamma-ray
source and compare it with the theoretical emission expected from hadronic and
leptonic populations accelerated in the radio jets. We argue that the gamma-ray
source could be powered by particles accelerated in the S255 NIRS 3 jets,
radiating via Bremsstrahlung or proton-proton interaction, and with a
synchrotron component shinning in radio from primary or secondary electrons in
the case of a leptonic or hadronic population.Comment: accepted for publication in Monthly Notices of the Royal Astronomical
Societ
Performance of the Large-Sized Telescope prototype of the Cherenkov Telescope Array
The next-generation ground-based gamma-ray Cherenkov Telescope Array
Observatory (CTAO) will consist of imaging atmospheric Cherenkov telescopes
(IACTs) of three different sizes distributed in two sites. The Large-Sized
Telescopes will cover the low-energy end of the CTA energy range, starting at
about 20 GeV. After its first years of operation at the CTA northern site, the
Large-Sized Telescope prototype (LST-1) is in the final stage of its
commissioning phase, having collected a significant amount of scientific data
to date.
In this contribution, we present the physics performance of the telescope
using low-zenith Crab Nebula observations and Monte Carlo simulations
fine-tuned accordingly. We show performance figures of merit such as the energy
threshold, effective area, energy and angular resolution, and sensitivity based
on the standard Hillas-parameters approach and following the source-independent
and dependent analysis methods. The analysis threshold is estimated at 30 GeV.
The energy resolution is around 30%, and the angular resolution is 0.3 degrees
at 100 GeV. The best integral sensitivity of LST-1 is about 1.1% of the Crab
Nebula flux above 250 GeV for 50 hours of observations. We also show the
spectral energy distribution and light curve from Crab Nebula observations,
which agree with results from other IACTs and link smoothly with Fermi-LAT when
considering statistical and systematic uncertainties near the energy threshold.Comment: Presented at the 38th International Cosmic Ray Conference (ICRC
2023), 2023 (arXiv:2309.08219
Tráficos portuarios por mercancía en España (1995-2010): análisis económico a partir de las importaciones y exportaciones
RESUMEN. En esta investigación se analizan las funciones de demanda de importaciones
y exportaciones de los tráficos portuarios españoles por
tipo de mercancía según Clasificación Uniforme para el Comercio Internacional
(CUCI) de las Naciones Unidas. A partir de un modelo teórico
convencional se formulan las hipótesis básicas respecto al comportamiento
de la demanda para los precios de las mercancías, los precios
del transporte y los diferentes niveles de renta. Después de exponer las
fuentes estadísticas de los datos, se estiman las elasticidades respecto
al precio de la mercancía, al precio del servicio de transporte marítimo
y se realizan una serie de previsiones respecto al comportamiento de la
demanda.ABSTRACT. This research analyzes the demand functions for imports and exports
for Spanish port traffics by type of goods according to the Standard International
Trade Classification (United Nations, 2006). From a conventional
theoretical model, the basic hypotheses are formulated regarding
the behaviour of the demand for goods prices, transport prices and the
different levels of income. After that, the price elasticities are estimated
respect to the price of the merchandise, the price of shipping service
and income. Finally, a series of provisions regarding the behaviour of
demand against the changes in prices and income are mad
A Single Nucleotide Polymorphism in the Il17ra Promoter Is Associated with Functional Severity of Ankylosing Spondylitis
The aim of this study was to identify new genetic variants associated with the severity of ankylosing spondylitis (AS). We sequenced the exome of eight patients diagnosed with AS, selected on the basis of the severity of their clinical parameters. We identified 27 variants in exons and regulatory regions. The contribution of candidate variants found to AS severity was validated by genotyping two Spanish cohorts consisting of 180 cases/300 controls and 419 cases/656 controls. Relationships of SNPs and clinical variables with the Bath Ankylosing Spondylitis Disease Activity and Functional Indices BASDAI and BASFI were analyzed. BASFI was standardized by adjusting for the duration of the disease since the appearance of the first symptoms. Refining the analysis of SNPs in the two cohorts, we found that the rs4819554 minor allele G in the promoter of the IL17RA gene was associated with AS (p<0.005). This variant was also associated with the BASFI score. Classifying AS patients by the severity of their functional status with respect to BASFI/disease duration of the 60th, 65th, 70th and 75th percentiles, we found the association increased from p60 to p75 (cohort 1: p<0.05 to p<0.01; cohort 2: p<0.01 to p<0.005). Our findings indicate a genetic role for the IL17/ILRA axis in the development of severe forms of AS
- …