1,540 research outputs found
A new approach of analyzing GRB light curves
We estimated the Txx quantiles of the cumulative GRB light curves using our
recalculated background. The basic information of the light curves was
extracted by multivariate statistical methods. The possible classes of the
light curves are also briefly discussed.Comment: 4 pages, 8 figure
The three-dimensional carrier-envelope-phase map of focused few-cycle pulsed Gaussian beams
We derive an analytical expression that describes the complete
three-dimensional carrier-envelope phase (CEP) distribution of in the focal
volume of ultrashort pulsed Gaussian beams focused by spherical mirrors or
lenses. The focal CEP map depends on the so-called factor specifying the
frequency-dependence of the beam width of the source few-cycle pulse, on its
chirp and on the small chromatic aberration introduced by a lens without
appreciably distorting or broadening the few-cycle pulse. We show how to tailor
the CEP map of mirror-focused and lens-focused few-cycle pulses in order to
produce negligible transversal and axial CEP variations in specific regions of
the focal volume for phase-sensitive interactions of light with matter taking
place in a volume or on a surface. We propose a quasi-achromatic doublet lens
that can implement in practice these tailored CEP distributions.Comment: 9 pages, 6 figure
Searching for electromagnetic counterpart of LIGO gravitational waves in the Fermi GBM data with ADWO
The Fermi collaboration identified a possible electromagnetic counterpart of
the gravitational wave event of September 14, 2015. Our goal is to provide an
unsupervised data analysis algorithm to identify similar events in Fermi's
Gamma-ray Burst Monitor CTTE data stream. We are looking for signals that are
typically weak. Therefore, they can only be found by a careful analysis of
count rates of all detectors and energy channels simultaneously. Our
Automatized Detector Weight Optimization (ADWO) method consists of a search for
the signal, and a test of its significance. We developed ADWO, a virtual
detector analysis tool for multi-channel multi-detector signals, and performed
successful searches for short transients in the data-streams. We have
identified GRB150522B, as well as possible electromagnetic candidates of the
transients GW150914 and LVT151012. ADWO is an independently developed,
unsupervised data analysis tool that only relies on the raw data of the Fermi
satellite. It can therefore provide a strong, independent test to any
electromagnetic signal accompanying future gravitational wave observations.Comment: 4 pages and 4 figures, A&A Letters accepte
Dependence of the optical brightness on the gamma and X-ray properties of GRBs
The Swift satellite made a real break through with measuring simultaneously
the gamma X-ray and optical data of GRBs, effectively. Although, the satellite
measures the gamma, X-ray and optical properties almost in the same time a
significant fractions of GRBs remain undetected in the optical domain. In a
large number of cases only an upper bound is obtained. Survival analysis is a
tool for studying samples where a part of the cases has only an upper (lower)
limit. The obtained survival function may depend on some other variables. The
Cox regression is a way to study these dependencies. We studied the dependence
of the optical brightness (obtained by the UVOT) on the gamma and X-ray
properties, measured by the BAT and XRT on board of the Swift satellite. We
showed that the gamma peak flux has the greatest impact on the afterglow's
optical brightness while the gamma photon index and the X-ray flux do not. This
effect probably originates in the energetics of the jet launched from the
central engine of the GRB which triggers the afterglow.Comment: 2012 Fermi Symposium proceedings - eConf C12102
FIRE RESISTANCE FOR THIN-WEBBED CONCRETE AND MASONRY ELEMENTS
Deterioration of material characteristics and structural performance highly depends on constituents and temperature history. Material composition can also highly influence structural behaviour of elements. Thickness of web can be critical for high temperatures. The same situation is for interjoist elements (concrete or brick) between precast roof girders.First part of our study was to improve fire resistance by structural elements with a typical thin web. Our experimental study included fire tests on various concrete mixes and fire tests of the girder with simultaneous application of load. Second part of our study was to summarize the result of real fire cases for girder-slab systems with concrete or brick interjoists
Temperature dependent load bearing capacity of laminated glass panes
An experimental programme with numerous single and laminated glass specimens was carried out to study the temperature dependent behaviour of laminated glasses. The difference of load bearing capacities between the laminate manufactured from ordinary float (laminated glass) or tempered glass layers (safety laminated glass) were also studied in four-point bending. When glass laminate fractures, the interlayer can keep the fragments in place. Different types of interlayer materials, both resin and foil (type EVA) were studied in safety and non safety laminated glass specimens. Glasses are used not only in the interior but also in exterior places. Therefore, the effect of temperature of -20o C, +23\r C and +60o C were investigated on bending characteristics of glasses. The main influencing factors on the load bearing capacity and bending characteristics of the glass specimens were investigated e.g. tempering, laminating and temperature
DEGREE OF DETERIORATION DUE TO FIRE IN LARGE CONCRETE HALLS
Present paper deals with the engineering consequences of the fire attack in
three halls in Budapest, Hungary. Material and structural behaviour are
analysed under high temperature, which is
%are based on practical observations
reached even 800 \circC in some cases. These fire attacks were again
lessons, which are important to be analysed
Factor analysis of the long gamma-ray bursts
We study statistically 197 long gamma-ray bursts, detected and measured in
detail by the BATSE instrument of the Compton Gamma-Ray Observatory. In the
sample 10 variables, describing for any burst the time behavior of the spectra
and other quantities, are collected. The factor analysis method is used to find
the latent random variables describing the temporal and spectral properties of
GRBs. The application of this particular method to this sample indicates that
five factors and the \REpk spectral variable (the ratio of peak energies in
the spectrum) describe the sample satisfactorily. Both the pseudo-redshifts
inferred from the variability, and the Amati-relation in its original form, are
disfavored.Comment: 5 pages, acceptod to A&
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