Natalie Hell FAU Erlangen, Dr. Remeis-Sternwarte Bamberg, ECAP & LLNL

Laboratory astrophysics: investigating the mystery of low charge states of Si in the HMXB Cyg X-1 (pdf)

In the high mass X-ray binary system Cyg X-1 the clumpy wind of the black hole’s companion star causes absorption dips in the observed lightcurves. While absorption lines of H- and He-like ions can already be detected in the non-dip spectra, absorption lines of colder, less ionized material (mainly Si and S) grow with increasing degree of dipping. Good knowledge of the rest wavelength of these lines is crucial for their application to spectral line diagnostics. However, experimental data especially for the lower ionization states can not usually be found in atomic databases and theoretical calculations are quite limited in their accuracy due to the high number of electrons. Therefore, we measured the K alpha spectrum of H- through F-like Si with the Lawrence Livermore National Laboratory electron beam ion trap (EBIT-I) and use the results to infer the Doppler shift of the lines observed in Cyg X-1.