Related papers: A Propos Crossing the Hertzsprung Gap
Horizontal branch (HB) morphology is a complex multiple-parameter problem. Besides the metallicity, two other leading parameters are the mass loss rate (MLR) and the initial He abundance of the HB progenitors. Using the STAREV stellar…
Some recent observations of the abundances of s-process, r-process, and alpha elements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born in a globular cluster and accreted…
Massive stars and their supernovae are prominent sources of radioactive isotopes, the observations of which thus can help to improve our astrophysical models of those. Our understanding of stellar evolution and the final explosive endpoints…
Stars do not simply pop up on the main sequence. Before the stars arrive on the zero-age main sequence, they form in the collapses of molecular clouds, gain matter through accretion processes, and compress their cores until hydrogen can…
Convection is ubiquitous in stars and occurs under many different conditions. Here we explore convection in main-sequence stars through two lenses: dimensionless parameters arising from stellar structure and parameters which emerge from the…
We present a phenomenological model of feedback in early-type galaxies that tracks the evolution of the interstellar medium gas mass, metallicity, and temperature. Modeling the star formation rate as a Schmidt law with a…
Using cosmological hydrodynamical simulations, we investigate the effects of hierarchical aggregation on the triggering of star formation in galactic-like objects. We include a simple star formation model to transform the cold gas in dense…
The first stars are assumed to be predominantly massive. Although, due to the low initial abundances of heavy elements the line-driven stellar winds are supposed to be inefficient in the first stars, these stars may loose a significant…
We present the physical and evolutionary properties of prestellar and protostellar clumps in the Herschel Infrared GALactic plane survey (Hi-GAL) in two large areas centered in the Galactic plane and covering the tips of the long Galactic…
Shell convection driven by nuclear burning in a stellar core is a common hydrodynamic event in the evolution of many types of stars. We encounter and simulate this convection (i) in the helium core of a low-mass red giant during core helium…
The evolution on the AGB and beyond is reviewed with respect to the origin of Wolf-Rayet central stars. We focus on thermal pulses due to their particular importance for the evolution of hydrogen deficient stars. It is shown that overshoot…
The orbits of stars in galaxies are generically chaotic: the chaotic behavior arises in part from the intrinsically grainy nature of a potential that is composed of point masses. Even if the potential is assumed to be smooth, however,…
Massive stars are linked with diverse astronomical processes and objects including star formation, supernovae and their remnants, cosmic rays, interstellar media, and galaxy evolution. Understanding their properties is of primary importance…
We use cosmological hydrodynamic simulations with unprecedented resolution to study the formation of primordial stars in an ionized gas at high redshifts. Our approach includes all the relevant atomic and molecular physics to follow the…
It has been shown that proton ingestion episodes can happen in the formation of hot-subdwarf stars, and that neutron-capture processes are possible in those cases. Moreover, some helium-rich hot subdwarfs display extraordinarily high…
When we look at a nearby galaxy, we see a mixture of foreground stars and bona fide extragalactic stars. I will describe what we need to do to get meaningful statistics on the massive star populations across the H-R diagram. Such a census…
The formation of massive stars may take place at relatively low accretion rates over a long period of time if the accretion can continue past the onset of core hydrogen ignition. The accretion may continue despite the formation of an…
Hot subdwarf (SD) stars are the stripped cores of red giant stars in transition to the white dwarf sequence. The B-type subdwarfs (sdB) are powered by helium fusion in the core, more evolved ones (sdO) by shell burning. Low mass SDs may…
Using a compilation of measurements of the stellar mass density as a function of redshift we can infer the cosmic star formation history. For z < 0.7 there is good agreement between the two star formation histories. At higher redshifts the…
The evolution of a zero metallicity 9 M_s star is computed, analyzed and compared with that of a solar metallicity star of identical ZAMS mass. Our computations range from the main sequence until the formation of a massive oxygen-neon white…