Discussing the physical meaning of the absorption feature at 2.1 keV in 4U 1538-52

Abstract

High resolution X-ray spectroscopy is a powerful tool for studying the nature of the matter surrounding the neutron star in X-ray binaries and its interaction between the stellar wind and the compact object. In particular, absorption features in their spectra could reveal the presence of atmospheres of the neutron star or their magnetic field strength. Here we present an investigation of the absorption feature at 2.1 keV in the X-ray spectrum of the high mass X-ray binary 4U 1538-52 based on our previous analysis of the XMM-Newton data. We study various possible origins and discuss the different physical scenarios in order to explain this feature. A likely interpretation is that the feature is associated with atomic transitions in an O/Ne neutron star atmosphere or of hydrogen and helium like Fe or Si ions formed in the stellar wind of the donor.

8 pages, 6 figures (three of them multi-panel figures), accepted for publication in Astronomische Nachrichten/Astronomical Notes

References in corpus (7)

• The XMM-Newton Serendipitous Survey. V. The Second XMM-Newton Serendipitous Source Catalogue
• Model X-ray Spectra of Magnetic Neutron Stars with Hydrogen Atmospheres
• Modelling mid-Z element atmospheres for strongly-magnetized neutron stars
• The first cyclotron harmonic of 4U 1538-52
• Detecting emission lines with XMM-Newton in 4U 1538-52
• Absorption features caused by oscillations of electrons on the surface of a quark star
• Investigating the nature of absorption lines in the Chandra X-ray spectra of the neutron star binary 4U 1820-30