880 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
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
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
A betonok fagy- és olvasztósóállóság-vizsgálati hámlásának lassulási folyamata
A betonok fagy-, illetve fagy- és olvasztósóállóság-vizsgálati hámlása időben lejátszódó folyamat, amely lassuló vagy gyorsuló jellegének korábban nem túl sok figyelmet szenteltünk. A hámlasztásos fagyasztási lassulás is viszonylag új fogalomnak tekinthető, amely fogalom ilyen elnevezésének a nemzetközi irodalomban sem találtuk a nyomát.
E cikkben – amelyet az NVKP 16-1-2016-0019 pályázati támogatásból dolgoztuk ki – a hámlasztásos fagyasztási lassulási feltételt tartalmazó szabványoknak a lassulási feltétellel kapcsolatos intézkedéseit, valamint a lassulási feltétel e szabványokon túlmenő továbbfejlesztésének lehetőségét mutatjuk be
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&
Spin gap and Luttinger liquid description of the NMR relaxation in carbon nanotubes
Recent NMR experiments by Singer et al. [Singer et al. Phys. Rev. Lett. 95,
236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon
nanotubes with an energy gap evident at low temperatures. Here, a comprehensive
theory for the magnetic field and temperature dependent NMR 13C spin-lattice
relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low
temperature properties are governed by a gapped relaxation due to a spin gap (~
30K), which crosses over smoothly to the Luttinger liquid behaviour with
increasing temperature.Comment: 5 pages, 1 figure, 1 tabl
Statistical analysis of the prompt and afterglow emission of the three groups of gamma-ray bursts
We investigated the main prompt and afterglow emission parameters of
gamma-ray bursts detected by the Burst Alert Telescope (BAT) and X-Ray
Telescope installed on the Swift satellite. Our aim was to look for differences
or connections between the different types of gamma-ray bursts, so we compared
the BAT fluences, 1-sec peak photon fluxes, photon indices, XRT early fluxes,
initial temporal decay and spectral indices. We found that there might be a
connection between the XRT initial decay index and XRT early flux/BAT photon
index. Using statistical tools we also determined that beside the duration and
hardness ratios, the means of the \gamma- and X-ray--fluences and the
\gamma-ray photon index differ significantly between the three types of bursts.Comment: 7th Huntsville Gamma-Ray Burst Symposium, GRB 2013: paper 27 in eConf
Proceedings C130414
The Kepler equation for inspiralling compact binaries
Compact binaries consisting of neutron stars / black holes on eccentric orbit
undergo a perturbed Keplerian motion. The perturbations are either of
relativistic origin or are related to the spin, mass quadrupole and magnetic
dipole moments of the binary components. The post-Newtonian motion of such
systems decouples into radial and angular parts. We present here for the first
time the radial motion of such a binary encoded in a generalized Kepler
equation, with the inclusion of all above-mentioned contributions, up to linear
order in the perturbations. Together with suitably introduced parametrizations,
the radial motion is solved completely
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