Exploring neutron stars' devouring nature through stellar wind studies - SSW

EXPLORING NEUTRON STARS' DEVOURING NATURE THROUGH STELLAR WIND STUDIES - CAMILLE DIEZ

The spectral and timing behaviour of High-Mass X-ray Binaries (HMXBs) offers a unique opportunity for the investigation of accretion onto compact objects and of wind structure in massive stars. The bright and persistent neutron star HMXB Vela X-1 is one of the key systems for such studies with both current and future instruments. It has a complex clumpy stellar wind, prominent cyclotron resonant scattering features (CRSFs) and strong flares. Understanding the variability of the system on both short time scales of a few hundreds seconds and along its 9d orbit with current instruments enables us to make predictions for future observations with XRISM and Athena and to devise the best observational strategy for Vela X-1.
Here, we analyse a new observation taken with XMM-Newton at orbital phase ~0.5 and follow the evolution of spectral parameters down to the pulse period (~300s) time-scale. The strong variability of absorption is associated with the presence of a large-scale wind structure combined with the variable line of sight as the neutron star moves along the orbit. In particular, we, for the first time, are able to trace the onset of the wakes with high time resolution and compare to predictions from simulations.