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Line Emission (line + emission)
Selected AbstractsDensity Diagnostic Using Stark Broadening of He I Spectral Line Emission from Rydberg LevelsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-9 2006M. Koubiti Abstract Neutral helium line spectra of the diffuse series observed under recombining plasma conditions, are used for electron density diagnostics. The method is similar to that using high members of the Balmer series of hydrogen or its isotopes. It is based on the comparison of experimental line spectra to calculated Stark profiles obtained with the Stark line shape code PPP. Among the required atomic data, the dipole reduced matrix elements have been calculated using a hydrogenic approximation. A good agreement was found between the behaviors of the Einstein coefficients calculated using this approximation and the available corresponding values found in the literature. It is demonstrated here through its application to JET data that for relatively dense plasmas this method gives promising results which are consistent with other measurements. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fluctuating Helium Emission in Optically Thick Divertor PlasmasCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2008F. B. Rosmej Abstract Simulations of the helium radiative properties carried out with the recently developed multi-level meta-stable resolved collisional-radiative code SOPHIA discovered new unique emission lines to analyze optically thick divertor plasmas relevant for ITER. The comparison of their time dependent line emission obtained from the NAGDIS-II plasma simulator experiments with time dependent temperature probe measurements shows a strong correlation. This indicates that line intensity fluctuations can be transformed to the important quantities of density and temperature fluctuations. A transformation method based on integral line intensity ratios which can be recorded with high time resolution is discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Entry dynamics and acoustics/infrasonic/seismic analysis for the Neuschwanstein meteorite fallMETEORITICS & PLANETARY SCIENCE, Issue 10 2004D. O. REVELLE This includes ground-based photographic and radiometer data as well as infrasound and seismic data from this very significant bolide event (Spurný et al. 2002, 2003). We have also used these data to model the entry of Neuschwanstein, including the expected dynamics, energetics, panchromatic luminosity, and associated fragmentation effects. In addition, we have calculated the differential efficiency of acoustical waves for Neuschwanstein and used these values to compare against the efficiency calculated using available ground-based infrasound data. This new numerical technique has allowed the source height to be determined independent of ray tracing solutions. We have also carried out theoretical ray tracing for a moving point source (not strictly a cylindrical line emission) and for an infinite speed line source. In addition, we have determined the ray turning heights as a function of the source height for both initially upward and downward propagating rays, independent of the explicit ray tracing (detailed propagation path) programs. These results all agree on the origins of the acoustic emission and explicit source heights for Neuschwanstein for the strongest infrasonic signals. Calculated source energies using more than four different independent approaches agree that Neuschwanstein was certainly <500 kg in initial mass, given the initial velocity of 20.95 km/s, resulting in an initial source energy ,0.0157-0.0276 kt TNT equivalent (4.185 times 1012 J). Local source energies at the calculated infrasonic/seismic source altitudes are up to two orders of magnitude smaller than this initial source energy. [source] Mapping low- and high-density clouds in astrophysical nebulae by imaging forbidden line emission,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009J. E. Steiner ABSTRACT Emission line ratios have been essential for determining physical parameters such as gas temperature and density in astrophysical gaseous nebulae. With the advent of panoramic spectroscopic devices, images of regions with emission lines related to these physical parameters can, in principle, also be produced. We show that, with observations from modern instruments, it is possible to transform images taken from density-sensitive forbidden lines into images of emission from high- and low-density clouds by applying a transformation matrix. In order to achieve this, images of the pairs of density-sensitive lines as well as the adjacent continuum have to be observed and combined. We have computed the critical densities for a series of pairs of lines in the infrared, optical, ultraviolet and X-rays bands, and calculated the pair line intensity ratios in the high- and low-density limit using a four- and five-level atom approximation. In order to illustrate the method, we applied it to Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (GMOS-IFU) data of two galactic nuclei. We conclude that this method provides new information of astrophysical interest, especially for mapping low- and high-density clouds; for this reason, we call it ,the ld/hd imaging method'. [source] On the relation between the coronal line emission and the infrared/X-ray emission in Seyfert galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002M. Almudena Prieto The relation between the X-ray, the coronal line and the infrared (IR) emissions in a sample of the brightest known Seyfert galaxies is analysed. A close relationship between the absorption-corrected soft X-ray emission and both the mid-IR and the coronal line emission is found for the Seyfert type 2 objects in the sample. The coronal line and the X-ray emissions are both main tracers of active galactic nuclei (AGN) activity and their relationship with the mid-IR emission points to the heat of the carbuncle dust as the main energetic process associated with the AGN. On the other hand, the above relations do not seem to hold for the type 1 Seyfert discussed in the sample, at least when the comparisons are made in a flux diagram. This is partially because of the reduced number of objects of this type analysed in this work and also the fact that the measured soft X-ray emission in Seyfert 1s is systematically larger, by at least an order of magnitude, than that in the Seyfert 2 counterparts. Finally, the hard X-ray emission in the studied sample appears unrelated to either the mid-IR or the coronal line emission. [source] The relation between extended radio and line emission for radio-loud quasarsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2001Xinwu Cao We explore the relationship between the extended radio and line emission for a radio-loud quasar sample including both core-dominated and lobe-dominated quasars. A strong correlation is present between the extended radio and broad-line emission. The core emission is also correlated with the broad-line emission for core-dominated quasars in the sample. The statistical behaviour of the core emission of lobe-dominated quasars is rather different from that of core-dominated quasars. The extended radio luminosity is a good tracer for jet power, while the core luminosity can only be a jet power tracer for core-dominated quasars. [source] Optical spectroscopy of GX 339,4 during the high,soft and low,hard states , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2001Line ionization, emission region We have carried out observations of the X-ray transient GX 339,4 during its high,soft and low,hard X-ray spectral states. Our high-resolution spectroscopic observation in 1999 April suggests that the H, line has a single-peaked profile in the low,hard state as speculated in our previous paper. The He ii,4686 line, however, has a double-peaked profile in both the high,soft and low,hard states. This suggests that the line-emission mechanism is different in the two states. Our interpretation is that double-peaked lines are emitted from a temperature-inversion layer on the accretion disc surface when it is irradiatively heated by soft X-rays. Single-peaked lines may be emitted from outflow/wind matter driven by hard X-ray heating. We have constructed a simple plane-parallel model and we use it to illustrate that a temperature-inversion layer can be formed at the disc surface under X-ray illumination. We also discuss the conditions required for the formation of temperature inversion and line emission. Based on the velocity separations measured for the double-peaked lines in the high,soft state, we propose that GX 339,4 is a low-inclination binary system. The orbital inclination is about 15° if the orbital period is 14.8 h. [source] A short introduction to broad and variable iron lines around black holesASTRONOMISCHE NACHRICHTEN, Issue 10 2006A. C. Fabian Abstract Accreting black holes often show iron line emission in their X-ray spectra. When this line emission is very broad or variable then it is likely to originate from close to the black hole. The theory and observations of such broad and variable iron lines are briefly reviewed here. In order for a clear broad line to be found, one or more of the following have to occur: high iron abundance, dense disk surface and minimal complex absorption. Several excellent examples are found from observations of Seyfert galaxies and Galactic Black Holes. In several cases there is strong evidence that the black hole is rapidly spinning. Further examples are expected as more long observations are made with XMM-Newton, Chandra and Suzaku. Intriguing instances of rapid variability of some narrow iron lines, both emission and absorption, have been reported. These may reflect variations in the irradiation or motion of physical structures on the accretion disk. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] General Relativity effects and line emissionASTRONOMISCHE NACHRICHTEN, Issue 10 2006G. Matt Abstract General Relativity effects (gravitational redshift, light bending, ,) strongly modify the characteristics of the lines emitted close to the Black Hole in Active Galactic Nuclei and Galactic Black Hole systems. These effects are reviewed and illustrated, with particular emphasis on line emission from the accretion disc. Methods, based on the iron line, to measure the two astrophysically relevant parameters of a Black Hole, the mass and spin, are briefly discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Relativistic Fe line emission and highly photoionized absorption in GROJ1655-40ASTRONOMISCHE NACHRICHTEN, Issue 10 2006M. Díaz Trigo Abstract We report on two XMM-Newton and simultaneous INTEGRAL observations of the microquasar GRO J1655-40 during its 2005 outburst. The source was most probably in its high-soft state during both observations. There is evidence for the presence of both a relativistically broadened Fe line providing strong support for the existence of a spinning black hole, and a highly photo-ionized absorber. The photo-ionized absorber is responsible for strong K absorption lines of Fe XXV and Fe XXVI in the EPIC pn spectra. The parameters of the highly-ionized absorber were different during the two observations. A less ionized absorber is present in the second observation, where the 0.5,200 keV luminosity of GRO J1655-40 decreased by around a half. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical and near-infrared observations of hard serendipitous Chandra sourcesASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003C.S. Crawford Abstract We have been carrying out a successful observational programme targeted at finding the highly obscured quasars that are thought to be the main contributors to the hard X-ray background. Out of 56 sources so far studied with optical and near-infrared imaging and spectroscopy, we have found three definite and a further twelve possible Type II quasars. Few sources show significant line emission, suggesting that the line photons are depleted by the large columns of obscuring matter. The redshift distribution of our sources shows a distinct peak at z , 1. The broad-band colours and magnitudes of the optical/near-infrared counterparts indicate that the light in these bands is dominated by the continuum of a massive bright galaxy. [source] | ||||||||||