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High Resolution Spectroscopy of 4U 1728-34 from a Simultaneous Chandra-RXTE Observation

A. D'Ai'·T. Di Salvo·R. Iaria·G. Lavagetto·N. R. Robba·L. Burderi·M. Mendez·M. van der Klis
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Abstract

We report on a simultaneous Chandra and RossiXTE observation of the LMXB atoll bursting source 4U 1728-34 performed on 2002 March 3-5. We fitted the 1.2-35 keV continuum spectrum with a blackbody plus a Comptonized component. An overabundance of Si by a factor of ~2 with respect to Solar abundance is required for a satisfactory fit. Large residuals at 6-10 keV can be fitted by a broad (FWHM ~ 1.6 keV) Gaussian emission line, or, alternatively, by absorption edges associated with Fe I and Fe XXV at ~7.1 keV and ~9 keV, respectively. In this interpretation, we find no evidence of a broad, or narrow Fe Kalpha line, between 6 and 7 keV. We tested our alternative modeling of the iron Kalpha region by reanalyzing a previous BeppoSAX observation of 4U 1728-34, finding a general agreement with our new spectral model.

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A. D'Ai', T. Di Salvo, R. Iaria, G. Lavagetto, N. R. Robba, L. Burderi, M. Mendez, M. van der Klis. 2004-12-22. High Resolution Spectroscopy of 4U 1728-34 from a Simultaneous Chandra-RXTE Observation. https://doi.org/10.1063/1.2130281

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