Found 29 talks width keyword massive stars

Massive stars lose mass through powerful, radiatively driven stellar winds. Building on the original "CAK" model for steady, spherical winds driven by line-scattering, this talk will review recent research on the multi-faceted nature of such wind mass loss under varied conditions, for example due to rapid rotation, magnetic channeling, binary interaction, or a luminosity near the Eddington limit. An overall theme is that wind mass loss can in this way lead to a wide variety of astrophysical phenomena, including bipolar nebulae, massive star magnetospheres, colliding winds or compact companion accretion, and luminous blue variable eruption. The discussion here will summarize these with an emphasis on their varied observational signatures.

In this talk I consider two questions. First, I investigate the formation of molecular clouds from diffuse interstellar gas. It has been argued that the midplane pressure controls the fraction of molecular hydrogen present, and thus the star formation rate. Alternatively, I and others have suggested that the gravitational instability of the disk controls both. I present numerical results demonstrating that the observed correlations between midplane pressure, molecular hydrogen fraction, and star formation rate can be explained within the gravitational instability picture. Second, I discuss how ionization affects the formation of massive stars. Although most distinctive observables of massive stars can be traced back to their ionizing radiation, it does not appear to have a strong effect on their actual formation. Rather, I present simulations suggesting that stars only ionize large volumes after their accretion has already been throttled by gravitational fragmentation in the accretion flow. At the same time these models can explain many aspects of the observations of ultracompact H II regions.

Massive stars dominate the light output of entire galaxies, with luminosities in excess of 10⁵ L⊙. This makes them powerful probes with which to study a range of astrophysical phenomena. In this talk I will review the recent results of our group, in which we have been able to shed new light on the recent star-forming history of our Galaxy, and the nature of supernova progenitors. I will also discuss our latest project, which is to use massive stars as tracers of extra-galactic star-forming histories out to distances of 10 Mpc and beyond.

The formation of massive stars is not fully understood. The high luminosity and temperature of massive protostars complicate the accretion mechanism at work in intermediate and low mass young stellar objects. Nonetheless, several scenarios exist to explain the formation of massive stars. In this talk, we will focus on the process of triggered star formation on the borders of H II regions. Due to the feedback effects of OB stars, a layer of molecular material is collected during the expansion of the H II region. Instabilities develop in this layer and give birth to new stars. We will present a detailed study of three Galactic H II regions (RCW79, RCW82 and RCW120). Near-infrared integral field observations have been carried out with SINFONI on the VLT. We will see how they reveal the nature of both the ionizing stars and of the YSOs in the collected layer and how they support the scenario of 'triggered star formation'.

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.