Laboratory Measurements of the K-shell transition energies in L-shell ions of Si and S

Abstract

We have measured the energies of the strongest 1s-2ell (ell=s,p) transitions in He- through Ne-like silicon and sulfur ions to an accuracy of better than 1eV using Lawrence Livermore National Laboratory's electron beam ion traps, EBIT-I and SuperEBIT, and the NASA/GSFC EBIT Calorimeter Spectrometer (ECS). We identify and measure the energies of 18 and 21 X-ray features from silicon and sulfur, respectively. The results are compared to new Flexible Atomic Code calculations and to semi-relativistic Hartree Fock calculations by Palmeri et al. (2008). These results will be especially useful for wind diagnostics in high mass X-ray binaries, such as Vela X-1 and Cygnus X-1, where high-resolution spectral measurements using Chandra's high energy transmission grating has made it possible to measure Doppler shifts of 100km/s. The accuracy of our measurements is consistent with that needed to analyze Chandra observations, exceeding Chandra's 100km/s limit. Hence, the results presented here not only provide benchmarks for theory, but also accurate rest energies that can be used to determine the bulk motion of material in astrophysical sources. We show the usefulness of our results by applying them to redetermine Doppler shifts from Chandra observations of Vela X-1.

ApJ, in press

References in corpus (3)

• X-ray Spectral Study of the Photoionized Stellar Wind in Vela~X-1
• Beyond XSPEC: Towards Highly Configurable Analysis
• Dramatic Variability of X-ray Absorption Lines in the Black Hole Candidate Cygnus X-1

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• Measurement of n-resolved State-Selective Charge Exchange in Ne(8,9)+ Collision with He and H2
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system III. Dipping in the low/hard state
• High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare
• High-resolution Laboratory Measurements of K-shell X-ray Line Polarization and Excitation Cross Sections in Heliumlike S XV Ions
• Observing the onset of the accretion wake in Vela X-1
• Looking through the photoionisation wake: Vela X-1 at ${\phi }_{\mathrm{orb}}\approx 0.75$ with Chandra/HETG
• Chandra-HETGS Characterization of an Outflowing Wind in the accreting millisecond pulsar IGR J17591-2342
• A Critical Compilation of Experimental Data on the 1s2$l$2$l^{\prime }$ Core-Excited States of Li-like Ions from Carbon to Uranium
• Stellar wind variability in Cygnus X-1 from high-resolution excess variance spectroscopy with Chandra
• Cloudy in the microcalorimeter era: improved energies for Si and S K$\alpha$ fluorescence lines
• A Bayesian Approach for Strong Field QED Tests with He-like Ions