We present the results of a Chandra 30 ks observation of the low-mass X-ray binary and atoll source 4U 1705 - 44. Here we concentrate on the study of discrete features in the energy spectrum at energies below similar to 3 keV, as well as on the iron K alpha line, using the High Energy Transmission Grating Spectrometer on board the Chandra satellite. Below 3 keV, three narrow emission lines are found at 1.47, 2.0, and 2.6 keV. The 1.47 and 2.6 keV lines are probably identified with Ly alpha emission from Mg XII and S XVI, respectively. The identification of the feature at similar to 2.0 keV is uncertain because of the presence of an instrumental feature at the same energy. The iron K alpha line at similar to 6.5 keV is found to be intrinsically broad (FWHM similar to 1.2keV); its width can be explained by reflection from a cold accretion disk extending down to similar to 15 km from the neutron star center or by Compton broadening in the external parts of a hot (similar to 2 keV) Comptonizing corona. We finally report here precise X-ray coordinates of the source.
A broad iron line in the Chandra high energy transmission grating spectrum of 4U 1705-44
BURDERI, LUCIANO;
2005-01-01
Abstract
We present the results of a Chandra 30 ks observation of the low-mass X-ray binary and atoll source 4U 1705 - 44. Here we concentrate on the study of discrete features in the energy spectrum at energies below similar to 3 keV, as well as on the iron K alpha line, using the High Energy Transmission Grating Spectrometer on board the Chandra satellite. Below 3 keV, three narrow emission lines are found at 1.47, 2.0, and 2.6 keV. The 1.47 and 2.6 keV lines are probably identified with Ly alpha emission from Mg XII and S XVI, respectively. The identification of the feature at similar to 2.0 keV is uncertain because of the presence of an instrumental feature at the same energy. The iron K alpha line at similar to 6.5 keV is found to be intrinsically broad (FWHM similar to 1.2keV); its width can be explained by reflection from a cold accretion disk extending down to similar to 15 km from the neutron star center or by Compton broadening in the external parts of a hot (similar to 2 keV) Comptonizing corona. We finally report here precise X-ray coordinates of the source.
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