Completing the puzzle of the 2004-2005 outburst in V0332+53: the brightening phase included

TL;DR

This paper presents a detailed analysis of the 2004-2005 outburst of the X-ray pulsar V0332+53, focusing on the brightening phase, and finds no hysteresis in source parameters, providing tighter constraints on the magnetic field.

Contribution

First detailed analysis of the outburst brightening phase of V0332+53, revealing no hysteresis and refining magnetic field estimates.

Findings

Energy of cyclotron absorption line depends on luminosity similarly during brightening and fading.

No evidence of hysteresis in source parameters during the outburst.

Constraints on the magnetic field are improved by analyzing the full outburst sequence.

Abstract

Analysis of the data obtained with the RXTE observatory during a powerful outburst of the X-ray pulsar V0332+53 in 2004-2005 is presented. Observational data covering the outburst brightening phase are analysed in detail for the first time. A comparison of source parameters and their evolution during the brightening and fading phases shows no evidence for any hysteresis behaviour. It is found that the dependences of the energy of the cyclotron absorption line on the luminosity during the brightening and fading phases are almost identical. The complete data sequence including the outburst brightening and fading phases makes it possible to impose the more stringent constraints on the magnetic field in the source. The pulse profile and pulsed fraction are studied as functions of the luminosity and photon energy.