Continuum, cyclotron line, and absorption variability in the high-mass X-ray binary Vela X-1

Because of its complex clumpy wind, prominent cyclotron resonant scattering features, intrinsic variability, and convenient physical parameters (close distance, high inclination, small orbital separation), which facilitate the observation analysis system, Vela X-1 is one key systems for understanding accretion processes in high-mass X-ray binaries on all scales. We revisit with two new observations taken NuSTAR at phases ∼0.68–0.78 ∼0.36–0.52, show a plethora variability allow us to study geometry stellar wind properties system. follow evolution spectral down pulse period timescale using partially covered power law continuum Fermi-Dirac cutoff model local absorption. are able confirm anti-correlations between photon index luminosity and, low fluxes, folding energy luminosity, implying change Comptonising plasma. were not previously seen correlation line source overall observation, but we observed drop following strong flare. see absorption within (for ∼0.36–0.52 phases) that can be explained by presence large-scale structure, such as photoionisation wakes our variable sight through this structure.