Related papers: Nonlinear pulsations of red supergiants
The overstability of the fundamental radial mode in M dwarf models was theoretically predicted by Rodr\'iguez-L\'opez et al. (2012). The periods were found to be in the ranges ~25-40 min and ~4-8 h, depending on stellar age and excitation…
We calculated a grid of evolutionary tracks of rotating models with masses between 1.0 and 3.0 $M_{\odot}$ and a resolution $\delta M \leq 0.02$ $M_{\odot}$, which can be used to study the effects of rotation on stellar evolutions and on…
We present a dense model grid with tailored input chemical composition appropriate for the Large Magellanic Cloud. We use a one-dimensional hydrodynamic stellar evolution code, which accounts for rotation, transport of angular momentum by…
Several classes of pulsating stars are now known to undergo slow changes in amplitude; these include pulsating red giants and supergiants, and yellow supergiants. We have used visual observations from the AAVSO International Database, and…
We have used systematic, sustained visual observations from the AAVSO International Database, and the AAVSO time-series analysis package VSTAR to study the unexplained "long secondary periods" (LSPs) in 27 pulsating red giants. In our…
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.…
The evolution of rotating stars with zero-age main sequence (ZAMS) masses in the range 8 to 25 M_sun is followed through all stages of stable evolution. The initial angular momentum is chosen such that the star's equatorial rotational…
We present the results of the asteroseismic analysis of the red-giant star KIC 4351319 (TYC 3124-914-1), observed for 30 days in short-cadence mode with the Kepler satellite. The analysis has allowed us to determine the large and small…
Stars in the narrow mass range of about 2.5 and 3.5 solar masses can develop a thermally unstable He-burning shell during its ignition phase. We study, from the point of view secular stability theory, these so called thermal micropulses and…
The effects of rotation on stellar evolution are particularly important at low metallicity, when mass loss by stellar winds diminishes and the surface enrichment due to rotational mixing becomes relatively more pronounced than at high…
The nonlinear coupling between stellar convection and rotation is of great interest because it relates to understanding both stellar evolution and activity. We investigated the influence of rotation and the Coriolis force on the dynamics…
The evolutionary calculations for population I stars with masses on the main sequence 5 M_\odot <= M_0 <= 6.1 M_\odot and initial fractional abundances of helium Y_0=0.28 and heavier elements Z_0=0.02 were carried out to the stage of…
We calculate the evolution of massive stars, which undergo pulsational pair-instability (PPI) when the O-rich core is formed. The evolution from the main-sequence through the onset of PPI is calculated for stars with the initial masses of…
A massive star can enter the blue supergiant region either evolving directly from the main-sequence, or evolving from a previous red supergiant stage. The fractions of the blue supergiants having different histories depend on the internal…
Stars with masses of 80 - 130 Msun can encounter the pulsational pair-instability at the end of their lives, which triggers consecutive episodes of explosive burning that eject multiple massive shells. Collisions between these shells…
Evolutionary tracks of stars with masses on the main sequence $0.84M_\odot\le M_\textrm{ZAMS}\le 0.95M_\odot$ and initial metal abundances $Z=0.006$ and $Z=0.01$ were computed under various assumptions about the mass loss rate at the red…
Gravitational radiation tends to drive gravity modes in rotating neutron stars unstable. For an inviscid star, the instability sets in when the rotation frequency is about 0.7 times the corresponding mode frequency of the nonrotating star.…
A newly discovered instability in rotating neutron stars, driven by gravitational radiation reaction acting on the stars' $r$-modes, is shown here to set an upper limit on the spin rate of young neutron stars. We calculate the timescales…
Growing theoretical evidence suggests that the first generation of stars may have been quite massive (~100-300 solar masses). If they retain their high mass until death, such stars will, after about 3Myr, make pair-instability supernovae.…
Nuclear rings at centers of barred galaxies exhibit strong star formation activities. They are thought to undergo gravitational instability when sufficiently massive. We approximate them as rigidly-rotating isothermal objects and…