The fundamental cyclotron line in 4U 1538-52

TL;DR

This study analyzes RXTE observations of the X-ray pulsar 4U 1538-52, revealing correlations between cyclotron line parameters and discussing their implications for understanding the pulsar's magnetic field and accretion processes.

Contribution

It provides the first detailed analysis of cyclotron line variability and correlations in 4U 1538-52 using RXTE data, enhancing understanding of neutron star magnetic fields.

Findings

Correlations between cyclotron line width and energy.

Correlation between relative width and optical depth.

Implications for magnetic field and accretion physics.

Abstract

We present pulse phase averaged spectra of the high mass X-ray binary pulsar 4U 1538-52/QV Nor. Observations of this persistent accreting pulsar were made with the Rossi X-ray Timing Explorer (RXTE). We study the variability of cyclotron resonant scattering feature (CRSF or simply cyclotron line) in the high energy spectra of this binary system. We show that the parameters of the CRSF are correlated. The first one is, as suggested by theory, between the width and the energy of the cyclotron line. The second one is between the relative width and the optical depth of the cyclotron line. We discuss these results with studies of other X-ray pulsars and their implications on the line variability.