Found 25 talks width keyword massive stars
AbstractAsymptotic Giant Branch (AGB) stars are a principal source of gas and dust input into the interstellar medium, being an important driver of chemical evolution in galaxies. Rubidium is a key element to distinguish between high mass (~4-8 M⊙) AGB stars and low mass (~1-4 M⊙) AGBs - high mass AGBs are predicted to produce a lot of rubidium as a consequence of the genuine nucleosynthetic processes (the s-process) that characterise these stars. The Magellanic Clouds (MCs) offer a unique opportunity to study the stellar evolution and nucleosynthesis of AGB stars in low metallicity environments where distances (and so the star's luminosity) are known. We present the discovery of extragalactic rubidium-rich AGB stars in the MCs confirming that the more massive AGB stars are generally brighter than the standard adopted luminosity limit (Mbol~-7.1) for AGB's. In addition, massive MC-AGBs are more enriched in Rb than their galactic counterparts, as it is qualitatively predicted by the present theoretical models; the Rb over-abundance increase with increasing stellar mass and with decreasing metallicity. However, present theoretical models are far from matching the extremely high Rb overabundances observed.
The last decade has brought the discovery of a large number of massive (M > 10000 M?) young open clusters in the Milky Way, which had previously not been thought to exist. I will present a brief review of these discoveries, with strong emphasis on the use of these clusters as astrophysical laboratories. I will also present the very recent discovery of a number of massive clusters concentrated towards a small region of the Scutum Arm, providing evidence for the existence of starburst activity on a much larger scale than previously assumed.
AbstractThe Orion star forming region is an ideal laboratory for many astrophysical studies. In this talk I will present a study of the chemical composition of early B-type stars in the Orion OB1 association. The main ideas I will talk about are: (1) The importance of self-consistent spectroscopic techniques for the abundance analysis in this type of stellar objects; (2) the study of the homogeneity of abundances in stars from the various stellar subgroups in OriOB1; (3) the comparison of O stellar abundances with recent Solar determinations; (4) the comparison of stellar abundances with those resulting from the analysis of the emission line spectra of the Orion nebula (M42); (5) the study of the oxygen depletion onto dust grains in the Orion nebula. La región de formación estelar de Orión es una laboratorio perfecto para muchos tipos de estudios en astrofísica. En esta charla me centraré en el estudio de abundancias de las estrellas de tipo B temprano presentes en la asociación OriOB1. Las principales ideas que presentaré son: (1) La importancia de los análisis espectroscópicos detallados en la determinación de abundancias en estrellas de tipo B temprano; (2) el estudio de la homogeneidad química de los distintos subgrupos estelares que componen OriOB1; (3) la comparación de la abundancias estelares de oxígeno con determinaciones recientes en el Sol; (4) La comparación de abundancias estelares con aquellas obtenidas a partir de análisis del espectro de M42, la nebulosa de Orion; (5) el estudio de la depleción de oxígeno en granos de polvo en la nebulosa de Orión.
AbstractRadiation-driven mass loss largely determines the life expectancy of massive stars. I will present our most recent mass-loss predictions for massive stars, which are obtained from Monte-Carlo multi-line radiative transfer calculations. I will show how these predictions are expected to change as a function of metallicity (and redshift!) and confront the results against data from the VLT FLAMES large programme of massive stars. Finally, I discuss some of the more intricate aspects of the physics of radiation-driven outflows, emphasizing the relevance for the rotational evolution of massive stars into the Luminous Blue Variable phase. This is shown to lead to some rather unexpected results... in particular for the progenitors of supernovae and gamma-ray bursts -- calling for some major paradigm shifts of even our most basic framework of massive star evolution.
AbstractIn the first (optical) part, we present our recent results on mass and luminosity function of Galactic open clusters, a new statistical study based on the ASCC-2.5 catalogue of bright stars, complete to about 1 kpc around the Sun. This includes a new determination of the fraction of field stars born in open clusters. It also briefly addresses the issue whether all massive stars are exclusively born in clusters. In the second (infrared) part, we discuss the prospects of a 42m European ELT to "see" the origin of massive stars in dense embedded protoclusters, by penetrating dense proto- cluster clouds up to 200 mag of visual extinction at 2-5 microns. High-angular resolution AO imaging as well as 3D integral field spectroscopy are required to study the stellar density, binary content, and dynamical properties of these highly obscured, massive, compact star clusters.
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- IAU G5 -- The GALAH survey: science goals and highlights to dateSarah MartellTuesday January 25, 2022 - 10:30 GMT (Online)
- Dynamos, the drivers of solar and stellar activityProf. Axel BrandenburgThursday January 27, 2022 - 10:30 GMT (Online)