Column Densities Towards Three Bursting Low-Mass X-ray Binaries from High Resolution X-ray Spectroscopy

Abstract

We measured the galactic hydrogen column densities to the neutron-star binaries GX 17+2, 4U 1705-44, and 4U 1728-34 by modeling the Mg and Si absorption edges found in high-resolution X-ray spectra obtained by the Chandra X-ray Observatory. We found for GX 17+2, N_H = (2.38 +/- 0.12) x 10^22 cm^-2, for 4U 1705-44, N_H = (2.44 +/- 0.09) x 10^22 cm^-2, and for 4U 1728-34, N_H = (2.49 +/- 0.14) x 10^22 cm^-2. These values are in reasonable agreement with the hydrogen column densities inferred earlier from modeling of the continuum spectra of the sources. Our results can be used to constrain the uncertainties of model parameters of the X-ray spectra of these sources that are correlated to the uncertainties of the hydrogen column density. In the case of continuum spectra obtained during thermonuclear X-ray bursts, they will significantly reduce the uncertainties in the spectroscopically measured masses and radii of the neutron stars.

submitted to ApJ

References in corpus (1)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer

Cited by in corpus (3)

• The Distance, Mass, and Radius of the Neutron Star in 4U 1608-52
• Systematic Uncertainties in the Spectroscopic Measurements of Neutron-Star Masses and Radii from Thermonuclear X-ray Bursts. II. Eddington Limit
• A comparison of broad iron emission lines in archival data of neutron star low-mass X-ray binaries