# Observations of V0332+53 during the 2015 Outburst using Fermi/GBM, MAXI, Swift, and INTEGRAL

## TL;DR

This paper analyzes the 2015 outburst of the high mass X-ray binary V0332+53 using multiple space observatories, revealing changes in accretion dynamics and magnetic field strength through spectral and timing analysis.

## Contribution

It provides a comprehensive multi-instrument observational study of V0332+53's outburst, highlighting the evolution of accretion processes and magnetic field indicators.

## Key findings

- Characteristic X-ray emission features linked to orbital and accretion dynamics
- Decrease in critical luminosity indicating magnetic field weakening
- Identification of flow regime changes in the accretion column

## Abstract

We present the lightcurves, spectra, and hardness-intensity diagram (HID) of the high mass X-ray binary V0332+53 using Fermi/GBM, MAXI, Swift/BAT, and INTEGRAL through its 2015 Type II outburst. We observe characteristic features in the X-ray emission (2-50 keV) due to periastron passages, the dynamical timescale of the accretion disc, and changes within the accretion column between a radiation-dominated flow and a flow dominated by Coulomb interactions. Based on the HID and the light curves, the critical luminosity is observed to decrease by ~5-7 percent during the outburst, signaling a decrease in the magnetic field.