Orbital phase resolved spectroscopy of 4U1538-52 with MAXI

Abstract

4U 1538-52, an absorbed high mass X-ray binary with an orbital period of 3.73 days, shows moderate orbital intensity modulations with a low level of counts during the eclipse. Several models have been proposed to explain the accretion at different orbital phases by a spherically symmetric stellar wind from the companion. The aim of this work is to study both the light curve and orbital phase spectroscopy of this source in the long term. Particularly, the folded light curve and the changes of the spectral parameters with orbital phase to analyse the stellar wind of QV Nor, the mass donor of this binary system. We used all the observations made from the Gas Slit Camera on board MAXI of 4U 1538-52 covering many orbits continuously. We obtained the good interval times for every orbital phase range which were the input to extract our data. We estimated the orbital period of the system and then folded the light curves and we fitted the X-ray spectra with the same model for every orbital phase spectrum. We also extracted the averaged spectrum of all the MAXI data available. The MAXI spectra in the 2-20 keV energy range were fitted with an absorbed Comptonization of cool photons on hot electrons. We found a strong orbital dependence of the absorption column density but neither the fluorescence iron emission line nor low energy excess were needed to fit the MAXI spectra. The variation of the spectral parameters over the binary orbit were used to examine the mode of accretion onto the neutron star in 4U 1538-52. We deduce a best value of $\dot{M}/v_{\infty }=0.65\times 10^{-9}$ $M_{\odot }y{r}^{-1}/(km{s}^{-1})$ for QV Nor.

12 pages, 5 figures, accepted to be published by A&A, corrected typos (changing bold font to normal one)

References in corpus (7)

• The first cyclotron harmonic of 4U 1538-52
• A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522
• Neutron star masses from hydrodynamical effects in obscured sgHMXBs
• Orbital phase resolved spectroscopy of GX 301-2 with MAXI
• Measurements of Cyclotron Features and Pulse Periods in the High-Mass X-Ray Binaries 4U 1538-522 and 4U 1907+09 with INTEGRAL
• Peering through the stellar wind of IGR J19140+0951 with simultaneous INTEGRAL/RXTE observations
• Detecting emission lines with XMM-Newton in 4U 1538-52

Cited by in corpus (5)

• X-Ray Spectra of The High-Mass X-RAY Binary 4U~1700-37 using BeppoSAX, Suzaku and RXTE Observations
• Evidence for an Evolving Cyclotron Line Energy in 4U 1538-522
• Cosmological implications of the composite spectra of galactic X-ray binaries constructed using MAXI data
• Variability study of the High Mass X-ray Binary IGR J18027--2016 with {\it Swift}--XRT
• Stellar wind parameters of massive stars in accretion-powered High Mass X-ray Binary Pulsars