A Chandra survey of fluorescence Fe lines in X-ray Binaries at high resolution - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: In this paper we present a comprehensive survey of 41 X-ray binaries 10HMXBs and 31 LMXBs with Chandra, with specific emphasis on the Fe K region andthe narrow Fe Kalpha line, at the highest resolution possible. We find that: aThe Fe Kalpha line is always centered at 1.9387 +- 0.0016 Angstroms, compatiblewith Fe I up to Fe X; we detect no shifts to higher ionization states nor anydifference between HMXBs and LMXBs. b The line is very narrow, with FWHM < 5mAngstroms, which means that the reprocessing material is not rotating at highspeeds. c Fe Kalpha fluorescence is present in all the HMXB in the surveywhile such emissions are very rare ~ 10% among LMXBs. d The lack of Fe lineemission is always accompanied by the lack of any detectable K edge. e Weobtain the empirical curve of growth of the equivalent width of the Fe Kalphaline versus the density column of the reprocessing material, i.e. EW {Kalpha}vs N {H}, and show that it is consistent with a reprocessing region sphericallydistributed around the compact object. f We show that fluorescence in X-raybinaries follows the X-ray Baldwin effect. We interpret this finding asevidence of decreasing neutral Fe abundance with increasing X-ray illuminationand use it to explain some spectral states of Cyg X-1 and as a possible causeof the lack of narrow Fe line emission in LMXBs. g Finally, we study anomalousmorphologies. We present the first evidence of a Compton shoulder in the HMXBX1908+075. Also the Fe Kalpha lines of 4U1700-37 and LMC X-4 present asymmetricwings suggesting the presence of highly structured stellar winds in thesesystems.



Autor: J.M. Torrejon, N.S. Schulz, M.A. Nowak, T.R. Kallman

Fuente: https://arxiv.org/







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