Low charge states of Si and S in Cygnus X-1
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Author/Creator ORCID
Date
2013-09-23
Type of Work
Department
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Citation of Original Publication
Hell, Natalie, I. Miškovičová, G. V. Brown, J. Wilms, J. Clementson, M. Hanke, P. Beiersdorfer, et al. “Low Charge States of Si and S in Cygnus X-1.” Physica Scripta 2013, no. T156 (September 2013): 014008. https://doi.org/10.1088/0031-8949/2013/T156/014008.
Rights
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0
Public Domain Mark 1.0
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Abstract
Strong, relatively short, absorption dips have been observed in the x-ray light curves measured from the high mass x-ray binary system Cygnus X-1. With increasing strength of the dips, which are believed to be caused by 'clumps' of cold material present in the stellar wind of Cyg X-1's companion star, K-shell absorption lines in L-shell ions of Si and S develop. To determine the bulk motion of the clumps via the Doppler shifts of these lines with high accuracy, we measured their reference energies using the Lawrence Livermore National Laboratory electron beam ion trap EBIT-I and EBIT Calorimeter Spectrometer. Our findings—shifts consistent with zero velocity of the absorber throughout all ionization states at orbital phase zero—provide evidence for an onion-like ion structure of the clumps.