2003/03/13 by Bram Boroson, B. Boroson, Saeqa Dil Vrtilek +5 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #astro-ph
paper · pdf · doi:10.1086/375636
published as Astrophys.J. 592 (2003) 516-531 · 43 pages, 12 figures (4 in color), submitted to The Astrophysical Journal
arxiv created 2003/03/13 · openalex publication_date 2003/07/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
Chandra X-Ray Observatory grating spectra of the supergiant X-ray binary 4U 1700-37 reveal emission lines from hydrogen- and helium-like S, Si, Mg, and Ne in the 4-13 Å range. The spectrum also shows fluorescent lines from S and Si and a prominent Fe Kα line at 1.94 Å. The lines contribute to the previously unaccounted "soft excess" in the flux in this range at orbital ϕ ≈ 0.7. The X-ray source was observed during intermittent flaring, and the strengths of the lines vary with the source state. The widths of the lines (FWHM ≈ 1000-2000 km s -1 ) can result from either Compton scattering or Doppler shifts. Power spectra of the hard X-rays show red noise, and the soft X-rays and lines show in addition quasi-periodic oscillations and a power spectral break. Helium-like triplets of Si and Mg suggest that the gas is not in a pure photoionization equilibrium. We discuss whether resonant scattering could affect the line ratios or whether a portion of the wind may be heated to temperatures T ~ 10 6 K.