Observations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.
A significant fraction of massive stars move at speed through the interstellar medium of galaxies. After their death as core collapse supernovae, a possible final evolutionary state is that of a fast rotating magnetised neutron star, shaping its circumstellar medium into a pulsar wind nebula. Understanding the properties of pulsar wind nebulae requires knowledge of the evolutionary history of their massive progenitors. Using 2.5D magnetohydrodynamical simulations, we demonstrate that, in the context of a runaway high mass red supergiant supernova progenitor, the morphology of its subsequent pu…
Polarization Diagnostics Applied to Coronal Mass Ejections and the Background Solar Wind
National Center for Atmospheric Research（国家大气研究中心）；Southwest Research Institute（西南研究所）；CIRES, University of Colorado（科罗拉多大学联合空间环境研究中心）；University of Colorado（科罗拉多大学）；Aberystwyth University（阿伯里斯特威斯大学）；Johns Hopkins University（约翰斯·霍普金斯大学）；Boston College（波士顿学院）
High resolution spectra of typical wind diagnostics ([OI] 6300 Å and other forbidden emission lines) can often be decomposed into multiple components: high-velocity components with blueshifts up to several 100 km/s are usually attributed to fast jets, while narrow (NLVC) and broad (BLVC) low-velocity components are believed to trace slower disc winds. Under the assumption that the line-broadening is dominated by Keplerian rotation, several studies have found that the BLVCs should trace gas launched between 0.05 and 0.5 au and correlations between the properties of BLVCs and NLVCs have been int…
We carry out a numerical experiment of ejecting winds in a massive colliding wind binary system, and quantifying the accretion onto the secondary star under different primary mass loss rates. We set a binary system comprising a Luminous Blue Variable (LBV) as the primary and a Wolf-Rayet (WR) star as the secondary, and vary the mass loss rate of the LBV to obtain different values of wind momentum ratio $η$. Our simulations include two sets of cases: one where the stars are stationary, and one that includes the orbital motion. As $η$ decreases the colliding wind structure moves closer to the se…
Line-driven winds of hot, luminous stars are intrinsically unstable due to the line-deshadowing instability (LDI). In non-magnetic hot stars, the LDI leads to the formation of an inhomogeneous wind consisting of small-scale, spatially separated clumps that can have great effects on observational diagnostics. However, for magnetic hot stars the LDI generated structures, wind dynamics, and effects on observational diagnostics have not been directly investigated so far. We investigated the non-linear development of LDI generated structures and dynamics in a magnetic line-driven wind of a typical …
Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostics
The $^{26}$Al short-lived radioactive nuclide is the source of the observed galactic diffuse $γ$-ray emission at 1.8 MeV. While different sources of $^{26}$Al have been explored, such as AGB stars, massive stars winds, and supernovae, the contribution of very massive stars has never been studied. We study the stellar wind contribution of very massive stars, i.e stars with initial masses between 150 and 300 M$_\odot$, to the enrichment in $^{26}$Al of the galactic interstellar medium. We discuss the production of $^{26}$Al by studying rotating and non-rotating very massive stellar models with i…
Disc winds and planet formation are considered to be two of the most important mechanisms that drive the evolution and dispersal of protoplanetary discs and in turn define the environment in which planets form and evolve. While both have been studied extensively in the past, we combine them into one model by performing three-dimensional radiation-hydrodynamic simulations of giant planet hosting discs that are undergoing X-ray photo-evaporation, with the goal to analyse the interactions between both mechanisms. In order to study the effect on observational diagnostics, we produce synthetic obse…
Massive protostars attain high luminosities as they are actively accreting and the radiation pressure exerted on the gas in the star's atmosphere may launch isotropic high-velocity winds. These winds will collide with the surrounding gas producing shock-heated ($T\sim 10^7$ K) tenuous gas that adiabatically expands and pushes on the dense gas that may otherwise be accreted. We present a suite of 3D radiation-magnetohydrodynamic simulations of the collapse of massive prestellar cores and include radiative feedback from the stellar and dust-reprocessed radiation fields, collimated outflows, and,…
由于计算的要求和数值计算的困难与坐标奇异性在球面几何，完全动态的三维磁流体动力学（MHD）模拟的大质量星风是不容易的。在这里，我们报告的第一个这样的三维模拟使用$θ^1$ Ori C（O5.5 V）作为模型的初步结果。倾斜磁旋转体$θ^1$ Ori C是其环星环境中的硬X射线发射等离子体源。我们的数值模型可以解释这颗恒星的硬度和X射线发射的位置，证实磁约束风激波（MCWS）是一些大质量恒星中硬X射线的主要机制。
The mass-loss rates of massive helium stars are one of the major uncertainties in modern astrophysics. Regardless of whether they were stripped by a binary companion or managed to peel off their outer layers by themselves, the influence and final fate of helium stars -- in particular the resulting black hole mass -- highly depends on their wind mass loss as stripped-envelope objects. While empirical mass-loss constraints for massive helium stars have improved over the last decades, the resulting recipes are limited to metallicities with the observational ability to sufficiently resolve individ…
3-D Radiative Transfer Modeling of Structured Winds in Massive Hot Stars with Wind3D
利用Wind3D辐射转移（RT）程序，我们建立了大质量热星结构风的三维模型。我们研究了在B型超巨星HD 64760的风中观测到的大尺度结构的物理性质，并对Si IV λ1395中的离散吸收分量（DAC）和转动调制进行了详细的线轮廓拟合。我们开发参数化输入模型Wind3D与大规模的赤道风密度和速度结构，或所谓的“同向旋转相互作用区”（CIR）和“旋转调制区”（RMR）。参数化模型提供了高性能RT计算从头算流体动力学输入模型的重要优势。输入模型计算的加速使我们能够模拟和研究大质量热恒星扩展风中的各种物理条件。新的建模方法是非常灵活的约束HD 64760中的RMR的动态和几何风特性。我们计算的调制产生的径向密度增强，几乎线性地突出到赤道风的规则模式。我们发现，调制所造成的狭窄的“辐条状”风区。我们提出的流体动力学模型表明，线性形状的径向风图案可以引起的机械波作用在底部的恒星风从蓝超巨星。
The SWICS instrument aboard the ACE satellite has detected frequent intervals in the slow solar wind and interplanetary coronal mass ejections (ICMEs) in which C6+ and other fully stripped ions are strongly depleted, though the ionization states of elements such as Si and Fe indicate that those ions should be present. It has been suggested that these outlier or dropout events can be explained by the resonant cyclotron heating process, because these ions all have the same cyclotron frequency as He2+. We investigate the region in the corona where these outlier events form. It must be above the i…
