Stellar Evolution Theory Stellar Evolution Observations Raphael Hirschi

Stellar Evolution (Theory) – Stellar Evolution (Observations) Raphael Hirschi and Andreas Korn What makes a star simple: hydrostatic equilibrium

MANY INSTABILITIES-TRANSPORT PROCESSES CONVECTION, SEMI-CONVECTION, MERIDIONAL CURRENTS, SHEAR TURBULENCE. . . MASS LOSS BY STELLAR WINDS MASS EXCHANGES/LOSSES IN CLOSE BINARIES WAVES DUE TO TIDES

THE CHALLENGES CONVECTION physics of the boundaries of the convective zones? how to go beyond the mixing length theory? MASS LOSSES impact of pulsation, dusts? origin/frequency/conditions for outbursts? ROTATION transport processes? origin of fast rotators? MAGNETIC FIELDS impact of wind magnetic braking? impact on the core rotation at the pre-SN stage? MULTIPLICITY Is mass transfer/CE phase the sole significant effects? How to handle with the numerous parameters?

THESE PROCESSES ARE INTERCONNECTED CONVECTION LIFETIME MASS LOSSES TRACKS IN THE HR DIAGRAM ROTATION MAGNETIC FIELDS MULTIPLICITY

CONVECTION Extrapolating the weather to determine the climate. Arnett & Meakin 2016, Reports on Progress in Physics, Volume 79, Issue 10, article id. 102901 Arnett & Meakin 2007 Cristini et al. 2017

If simple perfect laws uniquely rule the Universe, should not pure thought be capable of uncovering this perfect set of laws without having to lean on the crutches of tediously assembled observations? True, the laws to be discovered may be perfect, but the human brain is not. Left on its own, it is prone to stray, as many past examples sadly prove. In fact, we have missed few chances to err until new data freshly gleaned from nature set us right again for the next steps. Thus pillars rather than crutches are the observations on which we base our theories; and for theory of stellar evolution these pillars must be there before we can get far on the right track. Martin Schwarzschild (1958)

In theory, a lot of observations In observations, a lot of theory

The Large surveys

ASTEROSEISMOLOGY Eggenberger et al. 2018, in press

Evidences for changes in He in stars with homogeneous CNO: challenging the role of the hot-CNO cycle in the Hevariations in globular cluster stars Ivan Cabrera-Ziri Eclipsing binaries for indirect helium determination? Observe: positions in the HRD+orbit (masses of the two components) Tracks with the corresponding mass should go through the observed Position in the HR diagram at the same age. If the star are He-rich, no solution will be found from standard tracks

At 13 Gyr the star at the turn off have a mass of ~0. 75 Msol when Y=0. 248 ~0. 55 Msol 0. 400 Chantereau et al. 2017

Enhancement of Li in red giants Raghubar Singh Preservation? Extrenal source? In situ production? Privitera et al. 2016

Heavy elements formation in various formation sites Almuneda Arcones

- Merging of NSs (light & heavy) - CCSNe (light) - Magneto-rotational Sne (light & heavy) Short GRB – NS merging – kilonova Long GRB – collpasar- jet supernova Asa Skuladottir: heavy elements in dwarf spheroidal stars with very different heavy element content (jump in abundances due to rare important event) but need of a more weaker continuous source

3 D 1 D hydro-nucleosynthesis simulations of convective-reactive nucleosynthesis for yields and galactic chemical evolution Falk Herwig http: //www. chetec. eu/knowledge-hubs/stellar-modelling-directory

3 D 1 D hydro-nucleosynthesis simulations of convective-reactive nucleosynthesis for yields and galactic chemical evolution Falk Herwig GCE: A good fit can be obtained with many different assumptions, but can be used for nuclear physics constraints i-process in rapidly accreting WDs Merging of O- and C-shells CEMP r/s Cf Poster Clarkson H- , He-shell convection zone In a Pop III stars (80 Msol))

Image from Roland Diehl (2011)