Search results for "Space telescope"
showing 10 items of 123 documents
A New Look at Spitzer Primary Transit Observations of the Exoplanet HD 189733b
2014
Blind source separation techniques are used to reanalyse two exoplanetary transit lightcurves of the exoplanet HD189733b recorded with the IR camera IRAC on board the Spitzer Space Telescope at 3.6$\mu$m during the "cold" era. These observations, together with observations at other IR wavelengths, are crucial to characterise the atmosphere of the planet HD189733b. Previous analyses of the same datasets reported discrepant results, hence the necessity of the reanalyses. The method we used here is based on the Independent Component Analysis (ICA) statistical technique, which ensures a high degree of objectivity. The use of ICA to detrend single photometric observations in a self-consistent wa…
The influence of Fermi motion on the comparison of the polarization transfer to a proton in elastic e→p and quasi-elastic e→A scattering
2019
Abstract A comparison between polarization-transfer to a bound proton in quasi-free kinematics by the A ( e → , e ′ p → ) knockout reaction and that in elastic scattering off a free proton can provide information on the characteristics of the bound proton. In the past the reported measurements have been compared to those of a free proton with zero initial momentum. We introduce, for the first time, expressions for the polarization-transfer components when the proton is initially in motion and compare them to the 2H data measured at the Mainz Microtron (MAMI). We show the ratios of the transverse ( P x ) and longitudinal ( P z ) components of the polarization transfer in H 2 ( e → , e ′ p → …
Thermal Transport and Wiedemann-Franz Law in the Disordered Fermi Liquid
2014
We study thermal transport in the disordered Fermi liquid at low temperatures. Gravitational potentials are used as sources for finding the heat density and its correlation function. For a comprehensive study, we extend the renormalization group (RG) analysis developed for electric transport by including the gravitational potentials into the RG scheme. Our analysis reveals that the Wiedemann-Franz law remains valid even in the presence of quantum corrections caused by the interplay of diffusion modes and the electron electron interaction. In the present scheme this fundamental relation is closely connected with a fixed point in the multi-parametric RG-flow of the gravitational potentials.
TANAMI: Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry - II. Additional Sources
2018
TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of -30deg declination including high-resolution Very Long Baseline Interferometry (VLBI) imaging, radio, optical/UV, X-ray and gamma-ray studies. We have previously published first-epoch 8.4GHz VLBI images of the parsec-scale structure of the initial sample. In this paper, we present images of 39 additional sources. The full sample comprises most of the radio- and gamma-ray brightest AGN in the southern quarter of the sky, overlapping with the region from which high-energy (>100TeV) neutrino events have been found. We characterize the parsec-scale radio properties of the jets and compare with the quasi-simu…
Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron II. Observations of 3C 273 at minimum activity
2017
RadioAstron is a 10 m orbiting radio telescope mounted on the Spektr-R satellite, launched in 2011, performing Space Very Long Baseline Interferometry (SVLBI) observations supported by a global ground array of radio telescopes. With an apogee of about 350 000 km, it is offering for the first time the possibility to perform {\mu}as-resolution imaging in the cm-band. We present observations at 22 GHz of 3C 273, performed in 2014, designed to reach a maximum baseline of approximately nine Earth diameters. Reaching an angular resolution of 0.3 mas, we study a particularly low-activity state of the source, and estimate the nuclear region brightness temperature, comparing with the extreme one det…
F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
2012
The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars. In the current study we show and discuss the evolution of broad-band radio spectra, which are measured at ten frequencies between 2.64 and 142 GHz using the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. It is argued that these can be attributed to only two classes of variability mechanisms. The first four types are dominated by spectral evolution and can be described by a simple two-component syst…
Numerical study of broadband spectra caused by internal shocks in magnetized relativistic jets of blazars
2013
The internal-shocks scenario in relativistic jets has been used to explain the variability of blazars' outflow emission. Recent simulations have shown that the magnetic field alters the dynamics of these shocks producing a whole zoo of spectral energy density patterns. However, the role played by magnetization in such high-energy emission is still not entirely understood. With the aid of \emph{Fermi}'s second LAT AGN catalog, a comparison with observations in the $\gamma$-ray band was performed, in order to identify the effects of the magnetic field.
Nuclear medium effects in structure functions
2012
We discuss the nuclear-medium effects in the weak structure functions F2(x,Q2) and F3,(x,Q2) in the charged current neutrino and antineutrino induced deep inelastic reactions in some nuclei which are being used in the present or proposed neutrino oscillation experiments. Our study of the medium effects has been done using relativistic nuclear spectral functions which incorporates Fermi motion, binding energy and nucleon correlations. We also consider the pion and rho meson cloud contributions calculated from a microscopic model for meson-nucleus self-energies. Using these structure functions, the results for the differential cross section have been obtained and compared with some of the ava…
Observational Cosmology at High Redshift
2007
Summary. I offer a brief review of the evolution and present status of our observational knowledge of the high-redshift Universe. In particular, I focus on the different methods that have been devised to select distant objects, and the observational evidence in hand to support (or else) the standard evolutionary scenario. 1 How High is High? The study of objects at cosmological distances from us started in the 1960s with the discovery and identification of quasi-stellar radiosources. The explanation of the features observed in the optical spectra of these objects as highly redshifted hydrogen lines opened the door to the very distant Universe. For the next 30 years after the discovery of qu…
β decay of the very neutron-deficient Ge60 and Ge62 nuclei
2021
We report here the results of a study of the $\beta$ decay of the proton-rich Ge isotopes, $^{60}$Ge and $^{62}$Ge, produced in an experiment at the RIKEN Nishina Center. We have improved our knowledge of the half-lives of $^{62}$Ge (73.5(1) ms), $^{60}$Ge (25.0(3) ms) and its daughter nucleus, $^{60}$Ga (69.4(2) ms). We measured individual $\beta$-delayed proton and $\gamma$ emissions and their related branching ratios. Decay schemes and absolute Fermi and Gamow-Teller transition strengths have been determined. The mass excesses of the nuclei under study have been deduced. A total $\beta$-delayed proton-emission branching ratio of 67(3)% has been obtained for $^{60}$Ge. New information has…