999 research outputs found
New observations with the gamma ray imager SIGMA
Results from the use of the gamma ray telescope SIGMA are given. An identification and an extensive study was done of sources contributing to the emission of the Galactic center region above 30 keV. A strong line was observed at 480 keV from Nova Muscae, which may be interpreted as an annihilation line with a redshift due to the presence of a compact object. The soft x-ray tails observed by SIGMA in some transient sources already identified as soft x-ray transients might be a common characteristic of these objects and has to be explained. The unusual spectrum of NGC4151 with a break around 50 keV can characterize a particular state of this kind of object. If it is the case, it has interesting implications for the origin of the Cosmic Diffuse Background
Ariane 5 verification and associated test facilities
The philosophy of verification tests of the Ariane 5 launcher program is already established. It corresponds to the development and the ground and flight qualification phases for both unmanned and manned launches. The different types of test are outlined for the system, booster, main core and upper structures, allowing the identification of the associated test facilities which are described
Analysis and comparison of the national and regional emission inventories for the Greater Madrid Region through air quality simulations
Este trabajo presenta un análisis y una metodologÃa para la armonización de inventarios de emisiones utilizados en modelos de calidad del aire
The Pulse Scale Conjecture and the Case of BATSE Trigger 2193
The pulses that compose gamma-ray bursts (GRBs) are hypothesized to have the
same shape at all energies, differing only by scale factors in time and
amplitude. This "Pulse Scale Conjecture" is confirmed here between energy
channels of the dominant pulse in GRB 930214c (BATSE trigger 2193), the single
most fluent single-pulsed GRB that occurred before May 1998. Furthermore,
pulses are hypothesized to start at the same time independent of energy. This
"Pulse Start Conjecture" is also confirmed in GRB 930214c. Analysis of GRB
930214c also shows that, in general, higher energy channels show shorter
temporal scale factors. Over the energy range 100 KeV - 1 MeV, it is found that
the temporal scale factors between a pulse measured at different energies are
related to that energy by a power law, possibly indicating a simple
relativistic mechanism is at work. To test robustness, the Pulse Start and
Pulse Scale Conjectures were also tested on the four next most fluent
single-pulse GRBs. Three of the four clearly passed, with a second smaller
pulse possibly confounding the discrepant test. Models where the pulse rise and
decay are created by different phenomena do not typically predict pulses that
satisfy both the Pulse Start Conjecture and the Pulse Scale Conjecture, unless
both processes are seen to undergo common time dilation.Comment: 19 pages, 9 figures, analysis revised and extended, accepted to Ap
Ex-situ Tunnel Junction Process Technique Characterized by Coulomb Blockade Thermometry
We investigate a wafer scale tunnel junction fabrication method, where a
plasma etched via through a dielectric layer covering bottom Al electrode
defines the tunnel junction area. The ex-situ tunnel barrier is formed by
oxidation of the bottom electrode in the junction area. Room temperature
resistance mapping over a 150 mm wafer give local deviation values of the
tunnel junction resistance that fall below 7.5 % with an average of 1.3 %. The
deviation is further investigated by sub-1 K measurements of a device, which
has one tunnel junction connected to four arrays consisting of N junctions (N =
41, junction diameter 700 nm). The differential conductance is measured in
single-junction and array Coulomb blockade thermometer operation modes. By
fitting the experimental data to the theoretical models we found an upper limit
for the local tunnel junction resistance deviation of ~5 % for the array of
2N+1 junctions. This value is of the same order as the minimum detectable
deviation defined by the accuracy of our experimental setup
IGR J11215-5952: a hard X-ray transient displaying recurrent outbursts
The hard X-ray source IGRJ11215-5952 has been discovered with INTEGRAL during
a short outburst in 2005 and proposed as a new member of the class of
supergiant fast X-ray transients. We analysed INTEGRAL public observations of
the source field in order to search for previous outbursts from this transient,
not reported in literature.Our results are based on a systematic re-analysis of
INTEGRAL archival observations, using the latest analysis software and
instrument calibrations. We report the discovery of two previously unnoticed
outbursts, spaced by intervals of ~330 days, that occurred in July 2003 and May
2004. The 5-100keV spectrum is well described by a cut-off power law, with a
photon index of 0.5, and a cut-off energy ~15-20keV, typical of High Mass X-ray
Binaries hosting a neutron star. A 5-100keV luminosity of 3E36 erg/s has been
derived (assuming 6.2kpc, the distance of the likely optical counterpart). The
5-100keV spectral properties, the recurrent nature of the outbursts,together
with the reduced error region containing the blue supergiant star
HD306414,support the hypothesis that IGRJ11215-5952 is a member of the class of
the Supergiant Fast X-ray Transients.Comment: 4 pages, 4 figures, accepted for publication in Astronomy and
Astrophysics Letter
Comparison and Assessment of Two Emission inventories for the Madrid Region
Emission inventories are databases that aim to describe the polluting activities that occur across a certain geographic domain. According to the spatial scale, the availability of information will vary as well as the applied assumptions, which will strongly influence its quality, accuracy and representativeness. This study compared and contrasted two emission inventories describing the Greater Madrid Region (GMR) under an air quality simulation approach. The chosen inventories were the National Emissions Inventory (NEI) and the Regional Emissions Inventory of the Greater Madrid Region (REI). Both of them were used to feed air quality simulations with the CMAQ modelling system, and the results were compared with observations from the air quality monitoring network in the modelled domain. Through the application of statistical tools, the analysis of emissions at cell level and cell – expansion procedures, it was observed that the National Inventory showed better results for describing on – road traffic activities and agriculture, SNAP07 and SNAP10. The accurate description of activities, the good characterization of the vehicle fleet and the correct use of traffic emission factors were the main causes of such a good correlation. On the other hand, the Regional Inventory showed better descriptions for non – industrial combustion (SNAP02) and industrial activities (SNAP03). It incorporated realistic emission factors, a reasonable fuel mix and it drew upon local information sources to describe these activities, while NEI relied on surrogation and national datasets which leaded to a poorer representation. Off – road transportation (SNAP08) was similarly described by both inventories, while the rest of the SNAP activities showed a marginal contribution to the overall emissions
Persistent time intervals between features in solar flare hard X-ray emission
Several solar hard X-ray events (greater than 100 keV) were observed simultaneously with identical instruments on the Venera 11, 12, 13, 14, and Prognoz spacecraft. High time resolution (= 2 ms) data were stored in memory when a trigger occurred. The observations of modulation are presented with a period of 1.6 s for the event on December 3, 1978. Evidence is also presented for fast time fluctuations from an event on November 6, 1979, observed from Venera 12 and another on September 6, 1981, observed from the Solar Maximum Mission. Power spectrum analysis, epoch folding, and Monte Carlo simulation were used to evaluate the statistical significance of persistent time delays between features. The results are discussed in light of the MHD model proposed by Zaitsev and Stepanov
An improved time of flight gamma-ray telescope to monitor diffuse gamma-ray in the energy range 5 MeV - 50 MeV
A time of flight measuring device is the basic triggering system of most of medium and high energy gamma-ray telescopes. A simple gamma-ray telescope has been built in order to check in flight conditions the functioning of an advanced time of flight system. The technical ratings of the system are described. This telescope has been flown twice with stratospheric balloons, its axis being oriented at various Zenital directions. Flight results are presented for diffuse gamma-rays, atmospheric secondaries, and various causes of noise in the 5 MeV-50 MeV energy range
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