The XMM Newton and INTEGRAL observations of the supergiant fast X-ray transient IGR J16328-4726

TL;DR

This study uses simultaneous XMM-Newton and INTEGRAL observations to analyze the accretion processes and wind properties in the supergiant fast X-ray transient IGR J16328-4726, revealing variable luminosity, spectral changes, and wind inhomogeneities.

Contribution

First simultaneous multi-instrument observations of IGR J16328-4726 during periastron, providing new insights into accretion mechanisms and wind characteristics in SFXTs.

Findings

Luminosity varies from 4x10^{34} to 10^{36} erg/s.

Spectral index varies from 1.2 to 1.7.

Detection of iron lines indicating wind inhomogeneities.

Abstract

The accretion mechanism producing the short flares observed from the Supergiant Fast X-ray Transients (SFXT) is still highly debated and forms a major part in our attempts to place these X-ray binaries in the wider context of the High Mass X-ray Binaries. We report on a 216 ks INTEGRAL observation of the SFXT IGR J16328-4726 (August 24-27, 2014) simultaneous with two fixed-time observations with XMM Newton (33ks and 20ks) performed around the putative periastron passage, in order to investigate the accretion regime and the wind properties during this orbital phase. During these observations, the source has shown luminosity variations, from 4x10^{34} erg/s to 10^{36} erg/s, linked to spectral properties changes. The soft X-ray continuum is well modeled by a power law with a photon index varying from 1.2 up to 1.7 and with high values of the column density in the range 2-4x10^{23}/cm^2. We report on the presence of iron lines at 6.8-7.1 keV suggesting that the X-ray flux is produced by accretion of matter from the companion wind characterized by density and temperature inhomogeneities.