Related papers: Helium-like triplet diagnostics
We develop a novel statistical approach to identify emission features or set upper limits in high-resolution spectra in the presence of high background. The method relies on detecting differences from the background using smooth tests and…
We analyze the high-resolution X-ray spectrum of the supergiant O-star delta Orionis (O9.5II) with line ratios of He-like ions and a thermal plasma model, and we examine its variability. The O-supergiant delta Ori was observed in the…
High resolution spectra of the active binary Capella (G8 III + G1 III) covering the energy range 0.4-8.0 keV (1.5-30 Angstroms) show a large number of emission lines, demonstrating the performance of the HETGS. A preliminary application of…
Here we discuss the physical conditions in the emission line regions (ELR) of active galactic nuclei (AGN), with the special emphasize on the unresolved problems, e.g. the stratification of the Broad Line Region (BLR) or the failure of the…
This paper outlines a way to determine the ICF using only infrared data. We identify four line pairs, [NeIII] 36$\micron$/[NeII] 12.8$\micron$, [NeIII]~15.6$\micron$ /[NeII] 12.8$\micron$, [ArIII] 9$\micron$/[ArII] 6.9$\micron$, and [ArIII]…
Helium line observations towards 11 Galactic positions using Westerbork Synthesis Radio Telescope(WSRT) have been reported. These observations were made towards nearby positions where already hydrogen lines were detected at sufficiently…
We present the results of high resolution spectroscopy of the prototype polar AM Herculis observed with Chandra High Energy Transmission Grating. The X-ray spectrum contains hydrogen-like and helium-like lines of Fe, S, Si, Mg, Ne and O…
We carry out plasma diagnostic analyses for 123 planetary nebulae (PNe) and 42 H II regions using the N II and O II optical recombination lines (ORLs). New effective recombination coefficients for the N II and O II optical recombination…
The spectra of AGN from the ultraviolet to the near infrared, exhibit emission lines covering a wide range of ionisation states, from neutral species such as [O I] 6300A, up to [Fe XIV] 5303A. Here we report on some recent studies of the…
Resonant scattering of He I 1.0833$\mu$m triplet photons by metastable He 2 $^3$S$_1$ is studied for optical depths characteristic of H II regions. Regions with large He 2 $^3$S$_1$ column densities are predicted to have unusually broad,…
Aims: Hydrogen and helium line spectra are crucial diagnostic features for the quantitative analysis of OB stars. We compute synthetic spectra based on a hybrid non-LTE approach in order to test the ability of these models to reproduce…
We analyze spectropolarimetric data of the He I 1083~nm multiplet ($1s2s~^3\!S_1 - 1s2p~^3\!P^o_{2,1,0}$) during the X1 flare SOL2014-03-29T17:48, obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope. While…
We present an analysis of ten cool stars (Algol, Capella, Procyon, Eps Eri, Alpha Cen A&B, UX Ari, AD Leo, YY Gem, and HR1099) observed with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra X-ray Observatory.…
Efforts to benchmark astrophysical observations with X-ray laboratory measurements have been stymied by observed and measured differences of up to a factor of two in the ratio '3s/3d' of Fe XVII lines at ~17 \AA and ~15 \AA respectively.…
We have used an electron beam ion trap to measure electron-density-diagnostic line-intensity ratios for extreme ultraviolet lines from F XII, XIII, and XIV at wavelengths of 185-205 255-276 Angstroms. These ratios can be used as density…
An electron beam ion trap (EBIT) is used to measure extreme ultraviolet spectra between 10 nm and 25 nm from highly-charged ions of tungsten with an open 3d shell (W XLVIII through W LVI). We found that almost all strong lines are due to…
We present a simple, yet powerful column density diagnostic for plasmas enabled by X-ray microcalorimeter observations. With the recent developments of the spectral simulation code Cloudy, inspired by the high spectral resolution of the…
We present observations of SS 433 using the Chandra High Energy Transmission Grating Spectrometer. Many emission lines of highly ionized elements are detected with the relativistic blue and red Doppler shifts. The lines are measurably…
In this study we show how hydrogen and helium lines modelling can be used to make a diagnostic of active and eruptive prominences. One motivation for this work is to identify the physical conditions during prominence activation and…
New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of high-resolution X-ray spectra in which hydrogen- and helium-like ions are usually strong features. We present results from a new collisional-radiative plasma code,…