3-D Radiative Transfer Modeling of Structured Winds in Massive Hot Stars with Wind3D

TL;DR

This paper introduces Wind3D, a 3-D radiative transfer modeling tool for structured stellar winds, applied to HD 64760, revealing that wind modulations are caused by narrow, spoke-like density enhancements driven by base wave activity.

Contribution

The paper presents a flexible parameterized 3-D modeling approach for structured stellar winds, enabling detailed analysis of wind features like CIRs and RMRs with improved computational efficiency.

Findings

Wind3D effectively models large-scale wind structures.

Modulations are caused by narrow, spoke-like wind regions.

Radial wind patterns can result from base wave activity.

Abstract

We develop 3-D models of the structured winds of massive hot stars with the Wind3D radiative transfer (RT) code. We investigate the physical properties of large-scale structures observed in the wind of the B-type supergiant HD 64760 with detailed line profile fits to Discrete Absorption Components (DACs) and rotational modulations observed with IUE in Si IV {\lambda}1395. We develop parameterized input models Wind3D with large-scale equatorial wind density- and velocity-structures, or so-called `Co-rotating Interaction Regions' (CIRs) and `Rotational Modulation Regions' (RMRs). The parameterized models offer important advantages for high-performance RT calculations over ab-initio hydrodynamic input models. The acceleration of the input model calculations permits us to simulate and investigate a wide variety of physical conditions in the extended winds of massive hot stars. The new modeling method is very flexible for constraining the dynamic and geometric wind properties of RMRs in HD 64760. We compute that the modulations are produced by a regular pattern of radial density enhancements that protrude almost linearly into the equatorial wind. We find that the modulations are caused by narrow `spoke-like' wind regions. We present a hydrodynamic model showing that the linearly shaped radial wind pattern can be caused by mechanical wave action at the base of the stellar wind from the blue supergiant.