相关论文: X-ray absorption via K-alpha resonance complexes i…
It is shown that photoabsorption via autoionizing resonances may be appreciable and used for abundance analysis. Analogous to spectral lines, the `resonance oscillator strength' f_r may be defined and evaluated in terms of the differential…
K-shell photoabsorption cross sections for the isonuclear C I - C IV ions have been computed using the R-matrix method. Above the K-shell threshold, the present results are in good agreement with the independent-particle results of Reilman…
Extensive calculations of the atomic data required for the spectral modelling of the K-shell photoabsorption of oxygen ions have been carried out in a multi-code approach. The present level energies and wavelengths for the highly ionized…
Theoretical differential oscillator strengths related to monochromatic opacity due to K- and L-shell absorption from oxygen and iron ions are directly compared with the Chandra and Xmm-Newton spectra of Seyfert~1 galaxy MCG--6-30-15. We…
Recently X-ray photoabsorption in KLL resonances of O VI was predicted [Pradhan, Astrophys.J. Lett. 545, L165 (2000)], and detected by the Chandra X-ray Observatory [Lee et al, Astrophys. J. {\it Lett.}, submitted]. The required resonance…
Photoabsorption by and fluorescence of the K{\alpha} transitions in highly charged iron ions are essential mechanisms for X-ray radiation transfer in astrophysical environments. We study photoabsorption due to the main K{\alpha} transitions…
We investigate the effect of resonances in photoionization and recombination cross sections computed using the R-matrix method. Photoionization and recombination rates derived from high-resolution cross sections for oxygen ions are compared…
Photoabsorption of atomic oxygen in the energy region below the $\rm 1s^{-1}$ threshold in x-ray spectroscopy from {\it Chandra} and {\it XMM-Newton} is observed in a variety of x-ray binary spectra. Photoabsorption cross sections…
An analytical formula is developed to represent accurately the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the Kedge, a Rydberg series expression is used to fit R-matrix…
We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption…
We present the first comprehensive analysis of the argon K-edge absorption region (3.1-4.2 \AA) using high-resolution HETGS {\it Chandra} spectra of 33 low-mas X-ray binaries. Utilizing R-matrix theory, we computed new K photoabsorption…
We investigate the absorption structure of the oxygen in the interstellar medium by analyzing {\it XMM}-Newton observations of the low mass X-ray binary Sco X-1. We use simple models based on the O {\sc i} atomic cross section from…
Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the…
We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of the Li-like to Ca-like ions stages of Ni. Level-resolved, Breit-Pauli calculations were performed for the Li-like to Na-like stages.…
Reliable atomic data have been computed for the spectral modeling of the nitrogen K lines, which may lead to useful astrophysical diagnostics. Data sets comprise valence and K-vacancy level energies, wavelengths, Einstein $A$-coefficients,…
We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the K-shell Rydberg…
FUV echelle spectroscopy of the radio-quiet QSO H1821+643 (z = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) at 7 km/s resolution, reveals 4 definite O VI absorption line systems and one probable O VI absorber at…
(Abbrev.) We present high-resolution spectroscopy of the oxygen K-shell interstellar absorption edge in 7 X-ray binaries using the HETGS onboard Chandra. Using the brightest sources as templates, we found a best-fit model of 2 absorption…
This is the final report of a three-paper series on the K-shell photoabsorption and photoionization of trace elements, namely F, Na, P, Cl, K, Sc, Ti, V, Cr, Mn, Co, Cu and Zn. K lines and edges from such elements are observed in the X-ray…
Aimed at ionization balance and spectral analysis of UV and X-ray sources, we present self-consistent sets of photoionization cross sections, recombination cross sections, and rate coefficients for Li-like O VI and He-like O VII.…