Transient X-ray pulsar V0332+53: pulse phase-resolved spectroscopy and the reflection model

TL;DR

This study conducts detailed pulse phase- and luminosity-resolved spectroscopy of the transient X-ray pulsar V0332+53 across a wide luminosity range, revealing how spectral parameters vary with pulse phase and luminosity, and discussing these results within a reflection model framework.

Contribution

First comprehensive analysis of spectral variations with pulse phase and luminosity for V0332+53, incorporating a reflection model to explain cyclotron line formation.

Findings

Spectral parameters vary strongly with pulse phase.

Pattern of variability changes with luminosity.

Results support reflection model for cyclotron line formation.

Abstract

We present the results of the pulse phase- and luminosity-resolved spectroscopy of the transient X-ray pulsar V0332+53, performed for the first time in a wide luminosity range (1-40)x10^{37} erg/s during a giant outburst observed by the RXTE observatory in Dec 2004 - Feb 2005. We characterize the spectra quantitatively and built the detailed "three-dimensional" picture of spectral variations with pulse phase and throughout the outburst. We show that all spectral parameters are strongly variable with the pulse phase, and the pattern of this variability significantly changes with luminosity directly reflecting the associated changes in the structure of emission regions and their beam patterns. Obtained results are qualitatively discussed in terms of the recently developed reflection model for the formation of cyclotron lines in the spectra of X-ray pulsars.