Search results for "Lyman series"

showing 3 items of 3 documents

On X-ray Optical Depth in the Coronae of Active Stars

2007

We have investigated the optical thickness of the coronal plasma through the analysis of high-resolution X-ray spectra of a large sample of active stars observed with the High Energy Transmission Grating Spectrometer on Chandra. In particular, we probed for the presence of significant resonant scattering in the strong Lyman series lines arising from hydrogen-like oxygen and neon ions. The active RS CVn-type binaries II Peg and IM Peg and the single M dwarf EV Lac show significant optical depth. For these active coronae, the Lya/Lyb ratios are significantly depleted as compared with theoretical predictions and with the same ratios observed in similar active stars. Interpreting these decremen…

PhysicsLyman seriesAstrophysics (astro-ph)chemistry.chemical_elementFluxFOS: Physical sciencesAstronomy and AstrophysicsRadiusAstrophysicsAstrophysics::Cosmology and Extragalactic AstrophysicsAstrophysicsradiative transfer — stars: coronae — stars: late-type — X-rays: starsSpectral linesymbols.namesakeStarsNeonchemistrySpace and Planetary SciencesymbolsAstrophysics::Solar and Stellar AstrophysicsOptical depthLine (formation)
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Detection of X-ray Resonance Scattering in Active Stellar Coronae

2004

An analysis of Lyman series lines arising from hydrogen-like oxygen and neon ions in the coronae of the active RS CVn-type binaries II Peg and IM Peg, observed using the {\it Chandra} High Resolution Transmission Grating Spectrograph, shows significant decrements in the Ly$\alpha$/Ly$\beta$ ratios as compared with theoretical predictions and with the same ratios observed in similar active binaries. We interpret these decrements in terms of resonance scattering of line photons out of the line-of-sight; these observations present the first strong evidence for this effect in active stellar coronae. The net line photon loss implies a non-uniform and asymmetric surface distribution of emitting s…

Physicsstars: coronaePhotonLyman seriesstars: late-typeAstrophysics (astro-ph)chemistry.chemical_elementFOS: Physical sciencesAstronomy and AstrophysicsX-rays: starsAstrophysicsCoronal loopAstrophysics::Cosmology and Extragalactic AstrophysicsAstrophysicsIonStarssymbols.namesakeNeonchemistrySpace and Planetary Scienceradiative transfersymbolsAstrophysics::Solar and Stellar AstrophysicsOrder of magnitudeLine (formation)
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Nuclear charge radii of the even sulphur isotopesS32,S34, andS36and ofP31using muonic atoms

1985

Energies of muonic x rays of the Lyman series of the even sulphur isotopes /sup 32/S, /sup 34/S, and /sup 36/S and of natural phosphorus have been determined with absolute precisions up to 23 parts/10/sup 6/. Equivalent Barrett charge radii R/sub k/,..cap alpha.. have been deduced. Their differences between the sulphur isotopes amount to ..delta..R/sub k/,..cap alpha..( /sup 34/S- /sup 32/ S) = 29.7(1.4) am and ..delta..R/sub k/,..cap alpha..( /sup 36/S- /sup 34/ S) = 18.7(1.5) am. Combining these results with recent elastic electron scattering data, we obtain in a model-independent way ..delta../sup 1/2/( /sup 34/S- /sup 3/ 2S) = 23.1(1.2) am and ..delta../sup 1/2/( /sup 36/S- /sup 3/ 4S) …

Nuclear reactionPhysicsElastic scatteringNuclear and High Energy Physicssymbols.namesakeStable isotope ratioLyman seriessymbolsPhosphorus-31 NMR spectroscopyAtomic physicsPhosphorus IsotopesEffective nuclear chargeSpectral linePhysical Review C
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