Related papers: Why Do Stars Turn Red? II. Steady-State Envelope S…
In this series of papers, we address the long-standing question of why post-main-sequence stars expand into red giants (RGs) or red supergiants (RSGs). This paper aims to identify the key physical mechanism that drives stellar evolution…
Red supergiants (RSGs) are an evolved He-burning phase in the lifetimes of moderately high mass (10 - 25 solar mass) stars. The physical properties of these stars mark them as an important and extreme stage of massive stellar evolution, but…
Yellow Hypergiants (YHGs) are massive stars that are commonly interpreted to be in a post-red supergiant evolutionary state. These objects can undergo outbursts on timescales of decades, which are suspected to be due to instabilities in the…
In spite of the spectacular progress accomplished by stellar evolution theory some simple questions remain unanswered. One of these questions is ``Why do stars become Red Giants?''. Here we present a relatively simple analytical answer to…
The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to non-classical atmosphere models to interpret these regions.…
Red supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (<25Mo). For many years their location in the H-R diagram was at variance with the evolutionary models. Using the MARCS stellar atmosphere models, we have…
Red supergiants (RSGs) are an evolved stage in the life of intermediate massive stars (than than 25 solar masses). For many years, their location in the H-R diagram was at variance with the evolutionary models. Using the MARCS stellar…
When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant, in which convection occupies a large fraction of the star.…
This study investigates the physical origin of the critical metallicity required for the formation of cool supergiants, as revealed by stellar evolution models. Using grids of stellar models, we show that the terminal-age main-sequence…
The effective temperature (Teff) distribution of stellar evolution models along the red giant branch (RGB) is sensitive to a number of parameters including the overall metallicity, elemental abundance patterns, the efficiency of convection,…
We conduct one-dimensional stellar evolution simulations of red supergiant (RSG) stars that mimic common envelope evolution (CEE) and find that the inner boundary of the envelope convective zone moves into the initial envelope radiative…
We assume that the strong convection during core helium flash of low mass red giant branch (RBG) stars excite waves that propagate to the envelope, and find that the energy that these waves deposit in the envelope causes envelope expansion…
Red supergiants (RSGs) are evolved massive stars in a stage preceding core-collapse supernova. Understanding evolved-phases of these cool stars is key to understanding the cosmic matter cycle of our Universe, since they enrich the cosmos…
Performing a series of hydrodynamic stellar evolutionary simulations with \textsc{Mesa} (Module for Experiments in Stellar Astrophysics), we investigate the excitation and growth of radial pulsations of massive red supergiants (RSGs) with…
Deriving the physical properties of red supergiants (RSGs) depends upon accurate corrections for reddening by dust. We use our recent modeling of the optical spectra of RSGs to address this topic. We find: (1) Previous broad-band studies…
Massive stars less massive than ~30 Msol evolve into a red supergiant after the main sequence. Given a standard IMF, this means about 80% of all single massive stars will experience this phase. RSGs are dominated by convection, with a…
The evolution of massive stars is affected by a variety of physical processes including convection, rotation, mass loss and binary interaction. Because these processes modify the internal chemical abundance profiles in multiple ways…
The evolution of low-mass stars into red giants is still poorly understood. During this evolution the core of the star contracts and, simultaneously, the envelope expands -- a process known as the `mirror'. Additionally, there is a short…
Early-time observations of the Type II supernovae (SNe) 2013cu and 2013fs have revealed an interaction of ejecta with material near the star surface. Unlike the Type IIn SN2010jl, which interacts with a dense wind for ~1yr, the interaction…
Red supergiants (RSGs), which are progenitors of hydrogen-rich Type II supernovae (SNe), have been known to pulsate from both observations and theory. The pulsations can be present at core collapse and affect the resulting SN. However, SN…