相关论文: Wind line variability and intrinsic errors in obse…

Extreme helium stars are very rare low-mass supergiants in a late stage of evolution. They are probably contracting to become white dwarfs following a violent phase of evolution which caused them to become hydrogen-deficient giants,…

We seek to establish additional observational signatures of the effects of clumping in OB star winds. The action of clumping on strategic wind-formed spectral lines is tested to steer the development of models for clumped winds and thus…

An extensive modelling of CO line emission from the circumstellar envelopes around a number of carbon stars is performed. By combining radio observations and infrared observations obtained by ISO the circumstellar envelope characteristics…

The purpose of this work is to present an extensive grid of dynamical atmosphere and wind models for M-type AGB stars, covering a wide range of relevant stellar parameters. We used the DARWIN code, which includes frequency-dependent…

A small fraction of hot OBA stars host global magnetic fields with field strengths of the order of 0.1-10 kG. This leads to the creation of persistent surface structures (spots) in stars with sufficiently weak winds as a result of the…

We have studied variability of the spectral lines of the OB star $\delta $Ori A--the brightest component of the $\delta $Ori triple system. Forty spectra with signal-to-noise ratios $\approx$500--800 and a time resolution of four minutes…

Mass loss through stellar winds governs the evolution of stars on the asymptotic giant branch (AGB). In the case of carbon-rich AGB stars, the wind is believed to be driven by radiation pressure on amorphous carbon (amC) dust forming in the…

We present a prospective work undertaken on Spectro-Polarimetric INterferometry (SPIN). Our theoretical studies suggest that SPIN is a powerful tool for studying the mass loss from early type stars. Based on Monte Carlo simulations, we…

Cool, evolved stars undergo copious mass loss but the details of how the matter is returned to the ISM are still under debate. We investigated the structure and evolution of the wind at 5 to 50 stellar radii from Asymptotic Giant Branch and…

One of the key questions in Astrophysics concerns the issue of whether there exists an upper-mass limit to stars, and if so, what physical mechanism sets this limit, which might also determine if the upper-mass limit is metallicity (Z)…

Observations of active stars reveal highly non-uniform surface distributions of magnetic flux. Theoretical models considering magnetised stellar winds however often presume uniform surface magnetic fields, characterised by a single magnetic…

Line ratios in "fir" triplets of helium-like ions have proven to be a powerful diagnostic of conditions in X-ray emitting gas surrounding massive stars. Recent observations indicate that these ratios can be variable with time. The possible…

Stellar bowshock nebulae are arcuate shock fronts formed by the interaction of radiation-driven stellar winds and the relative motion of the ambient interstellar material. Stellar bowshock nebulae provide a promising means to measure…

It is observationally as well as theoretically well established that the winds of hot, massive OB-stars are highly structured on a broad range of spatial scales. This paper first discusses consequences of the small-scale structures…

Winds of massive stars are suspected to be inhomogeneous (or clumpy), which biases the measures of their mass loss rates. In High Mass X-ray Binaries (HMXBs), the compact object can be used as an orbiting X-ray point source to probe the…

We pesent models for the velocity structure in the supersonic part of hot star winds in order to estimate the effects of clumping in density and velocity. XSTAR (Kallman,2018) was used to calculate radiation pressure in spectral lines…

Stellar winds of cool main sequence stars are very difficult to constrain observationally. One way to measure stellar mass loss rates is to detect soft X-ray emission from stellar astrospheres produced by charge exchange between heavy ions…

Mass loss rates for the tenuous, hot winds of cool stars are extremely difficult to measure, yet they are a crucial ingredient in the stars' rotational evolution. We present a new method for measuring these mass loss rates in young,…

Measurements of stellar mass loss rates are used to assess how wind strength varies with coronal activity and age for solar-like stars. Mass loss generally increases with activity, but we find evidence that winds suddenly weaken at a…

OB stars are known to exhibit various types of wind variability, as detected in their ultraviolet spectra, amongst which are the ubiquitous discrete absorption components (DACs). These features have been associated with large-scale…