Search results for "SPECTRA"
showing 10 items of 3542 documents
BOOTES observation of GRB 080603B
2012
We report on multicolor photometry of long GRB080603B afterglow from BOOTES-1B and BOOTES-2. The optical afterglow has already been reported to present a break in the optical lightcurve at 0.12 ± 0.2 days after the trigger. We construct the lightcurve and the spectral energy distribution and discuss the nature of the afterglow.
Broadband spectral analysis of MXB 1659−298 in its soft and hard state
2018
The X-ray transient eclipsing source MXB 1659-298 went into outburst in 1999 and 2015. During these two outbursts the source was observed by XMM-Newton, nuSTAR, and Swift/XRT. Using these observations, we studied the broadband spectrum of the source to constrain the continuum components and to verify whether it had a reflection component, as is observed in other X-ray eclipsing transient sources. We combined the available spectra to study the soft and hard state of the source in the 0.45-55 keV energy range. We report a reflection component in the soft and hard state. The direct emission in the soft state can be modeled with a thermal component originating from the inner accretion disk plus…
Threshold expansion of Feynman diagrams within a configuration space technique
2000
The near threshold expansion of generalized sunset-type (water melon) diagrams with arbitrary masses is constructed by using a configuration space technique. We present analytical expressions for the expansion of the spectral density near threshold and compare it with the exact expression obtained earlier using the method of the Hankel transform. We formulate a generalized threshold expansion with partial resummation of the small mass corrections for the strongly asymmetric case where one particle in the intermediate state is much lighter than the others.
Nonlocally-induced (quasirelativistic) bound states: Harmonic confinement and the finite well
2015
Nonlocal Hamiltonian-type operators, like e.g. fractional and quasirelativistic, seem to be instrumental for a conceptual broadening of current quantum paradigms. However physically relevant properties of related quantum systems have not yet received due (and scientifically undisputable) coverage in the literature. In the present paper we address Schr\"{o}dinger-type eigenvalue problems for $H=T+V$, where a kinetic term $T=T_m$ is a quasirelativistic energy operator $T_m = \sqrt{-\hbar ^2c^2 \Delta + m^2c^4} - mc^2$ of mass $m\in (0,\infty)$ particle. A potential $V$ we assume to refer to the harmonic confinement or finite well of an arbitrary depth. We analyze spectral solutions of the per…
A Study of the Nuclear Structure at High Energy and Low Spin
1983
A novel method to study nuclear structure at low spin as a function of temperature is developed and used on 146,148Sm, 154,156Gd and 160,162Dy, by means of the (3He, α) reaction. The nuclear level density for a wide energy range is also studied. The γ-multiplicities and the first generation γ-ray spectra indicate a structure change in deformed nuclei at about 6 MeV.
High Resolution and Broad Band Spectra of Low Mass X-ray Binaries: A Comparison between Black Holes and Neutron Stars
2005
A common question about compact objects in high energy astrophysics is whether it is possible to distinguish black hole from neutron star systems with some other property that is not the mass of the compact object. Up to now a few characteristics have been found which are typical of neutron stars (like quasi periodic oscillations at kHz frequencies or type-I X-ray bursts), but in many respects black hole and neutron star systems show very similar behaviors. We present here a spectral study of low mass X-ray binaries containing neutron stars and show that these systems have spectral characteristics that are very similar to what is found for black hole systems. This implies that it is unlikel…
Clustering effects in 48Cr composite nucleus produced via the reaction 24Mg + 24Mg at the excitation energy of 60 MeV
2013
The reaction 24Mg + 24Mg was used to produce the composite nucleus 48Cr at 60 MeV of excitation energy where a narrow resonance (170 KeV) has been found by measuring the elastic and inelastic channels. To determine the occurrence of deformation of this compound nucleus and its possible connection with the resonances and the hypothetical cluster structure, evaporative Light Charged Particles (LCP) were measured and compared to Statistical Model (SM) predictions. The experiment was performed at LNL using the 8πLP apparatus. The comparison of the evaporation residue-LCP coincidence angular distributions and LCP energy spectra with SM calculations supports the presence of a very large deformati…
Revisiting a vector-tensor theory of gravitation
2011
A certain vector-tensor theory of gravitation has been recently studied. In this theory, the zero-order energy density of the vector field could play the role of dark energy. In such a case, the question is: could the theory explain current cosmological observations as well as the so-called concordance model? Previous papers on the subject only consider a reduced number of current observations. We consider a wider set of observations including supernovae of type Ia, cosmic microwave background anisotropies, and the power spectrum of the energy density fluctuations. Results imply that, for negligible scalar perturbations of the vector field, the theory does not work.
HIGH-RESOLUTION FOURIER TRANSFORM SPECTROSCOPY OF LANTHANUM IN Ar DISCHARGE IN THE NEAR-INFRARED
2013
A high-resolution spectrum of lanthanum has been recorded by a Fourier Transform spectrometer in the wavelength range from 833 nm to 1666 nm (6000 cm{sup –1} to 12,000 cm{sup –1}) using as light source a hollow cathode lamp operated with argon as the discharge carrier gas. In total, 2386 spectral lines were detected in this region, of which 555 lines could be classified as La I transitions and 10 lines as La II transitions. All La II transitions and 534 of these La I transitions were classified for the first time, and 6 of the La II transitions and 433 of the classified La I transitions appear to be new lines, which could not be found in the literature. The corresponding energy level data o…
PRECISE LABORATORY MEASUREMENTS OF TRANS-DCOOH AND TRANS-HCOOD FOR ASTROPHYSICAL OBSERVATIONS
2011
The rotational spectra of the mono-deuterated isotopologues of trans-formic acid, trans-DCOOH and trans-HCOOD, were investigated. In the millimeter- and submillimeter-wave frequency regions the Lamb-dip technique was exploited to obtain sub-Doppler resolution and to resolve the hyperfine structure due to the deuterium and hydrogen nuclei, thus enabling the accurate determination of the corresponding hyperfine constants. The experimental determination was supported by high-level quantum-chemical calculations at the coupled-cluster level of theory using large atomic-orbital basis sets. The Lamb-dip measurements were also supplemented by THz Doppler- limited measurements in order to extend the…