Modelling interstellar structures around Vela X-1. Issue 4 (5th December 2017)

• Record Type: Journal Article
• Authors: Gvaramadze, V V; Alexashov, D B; Katushkina, O A; Kniazev, A Y
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 474:Issue 4(2018)
• Page Start: 4421
• Page End: 4431
• Publication Date: 2017-12-05
• Subjects: MHD -- shock waves -- stars: individual: Vela X-1 -- ISM: bubbles; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stx3089
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We report the discovery of filamentary structures stretched behind the bow-shock-producing high-mass X-ray binary Vela X-1 using the SuperCOSMOS H-alpha Survey and present the results of optical spectroscopy of the bow shock carried out with the Southern African Large Telescope. The geometry of the detected structures suggests that Vela X-1 has encountered a wedge-like layer of enhanced density on its way and that the shocked material of the layer partially outlines a wake downstream of Vela X-1. To substantiate this suggestion, we carried out 3D magnetohydrodynamic simulations of interaction between Vela X-1 and the layer for three limiting cases. Namely, we run simulations in which (i) the stellar wind and the interstellar medium (ISM) were treated as pure hydrodynamic flows, (ii) a homogeneous magnetic field was added to the ISM, while the stellar wind was assumed to be unmagnetized, and (iii) the stellar wind was assumed to possess a helical magnetic field, while there was no magnetic field in the ISM. We found that although the first two simulations can provide a rough agreement with the observations, only the third one allowed us to reproduce not only the wake behind Vela X-1, but also the general geometry of the bow shock ahead of it.