Found 7 talks width keyword stellar kinematics

Spectroscopic analyses of stellar chemical compositions are model-dependent, and shortcomings in the models often limit the accuracy of the final results.  For late-type stars like our Sun, two of the main problems in present-day methods are that they assume the stellar atmosphere is a) one-dimensional (1D) and hydrostatic, and b) satisfies local thermodynamic equilibrium (LTE).  We can relax these assumptions simultaneously by performing detailed 3D non-LTE radiative transfer post-processing of 3D radiative-hydrodynamic model stellar atmospheres.  I shall give a brief overview of this approach, and illustrate its impact on carbon, oxygen, and iron abundances in late-type stars.

Exciting things may have happened sometimes to the stars we see in the sky today. For example, Betelgeuse, also known as Alpha-Ori, an M-type red supergiant, the 10th brightest sky in the sky (usually), may well have been a binary star in the past. Its rapid rotation, peculiarly large Galactic velocity, and unusual chemical abundances all point to it being kicked out from the birth environment and merging as a binary star. By comparing a Monte-Carlo stellar cluster population model with the observed populations of Galactic O- and B- type stars (progenitors of red supergiants), I will show that the story of Betelgeuse is not at all uncommon. In distant galaxies, closely related scenarios may give rise to peculiar core-collapse supernovae. I will conclude by briefly discussing how the diversity of such binary and triple stellar evolution histories reflects in the variety of the currently discovered core-collapse supernovae.

Massive stars (at least eight times as massive as the Sun) possess strong stellar winds driven by radiation. With the advent of the so called MiMeS collaboration, an increasing number of these massive stars have been confirmed to have global magnetic fields. Such magnetic fields can have significant influence on the dynamics of these stellar winds which are strongly ionized. Such interaction of the wind and magnetic field can generate copious amount of X-rays, they can spin the star down, they can also help form large scale disk-like structures. In this presentation I will discuss the nature of such radiatively-driven winds and how they interact with magnetic fields.

https://youtu.be/jKmifm17bno

The new generation of spectrometers designed for extreme precision radial velocities enable correspondingly precise stellar spectroscopy. It is now fruitful to theoretically explore what the information content would be if stellar spectra could be studied with spectral resolutions of a million or more, and to deduce what signatures remain at lower resolutions. Hydrodynamic models of stellar photospheres predict how line profiles shapes, asymmetries, and convective wavelength shifts vary from disk center to limb. Corresponding high-resolution spectroscopy across spatially resolved stellar disks is now practical using differential observations during exoplanet transits, thus enabling the testing of such models. A most demanding task is to understand and to model spectral microvariability toward the radial-velocity detection of also low-mass planets in Earth-like orbits around solar-type stars. Observations of the Sun-as-a-star with extreme precision spectrometers now permit searches for spectral-line modulations on the level of a part in a thousand or less, feasible to test against hydrodynamic models of various solar features.

Dwarf galaxies are a complex population. They comprise objects with young and old stellar populations, slow and fast rotation, as well as single- and multi-component structure. These characteristics show correlations with environmental density - we thus believe that dwarf galaxies hold a fossil record of how environment affected galaxy evolution. In this talk I will review and discuss recent progress on our understanding of dwarf galaxies in clusters, both from the observational and the modelling side. In particular, I will attempt to reconcile the proposed formation mechanisms of early-type dwarf galaxies - the most abundant population in clusters - with the continuous environmental influence predicted by cosmological simulations.

The vision for the use of the WHT in the coming decade is taking shape.   A key element is the construction and deployment of WEAVE, a wide-field massive-multiplex spectrograph.  With 1000 fibres and spectral resolutions of 5000 and 20000, the opportunities for discovery are tremendous.  Three key fields will be: Milky-Way and Local Group archaeology linked to the   Gaia mission; cosmology redshift surveys; and galaxy evolution studies linked to photometric surveys such as VISTA, UKIDSS, LOFAR, EUCLID, and  others. IAC has the opportunity to get involved in this important instrument for ORM from the beginning.