Grids of stellar models with rotation

Abstract

Context. In recent years, many very interesting observations have appeared concerning the positions of Wolf-Rayet (WR) stars in the Hertzsprung-Russell diagram (HRD), the number ratios of WR stars, the nature of Type Ibc supernova (SN) progenitors, long and soft gamma ray bursts (LGRB), and the frequency of these various types of explosive events. These observations represent key constraints on massive star evolution. Aims. We study, in the framework of the single-star evolutionary scenario, how rotation modifies the evolution of a given initial mass star towards the WR phase and how it impacts the rates of Type Ibc SNe. We also discuss the initial conditions required to obtain collapsars and LGRB. Methods. We used a recent grid of stellar models computed with and without rotation to make predictions concerning the WR populations and the frequency of different types of core-collapse SNe. Current rotating models were checked to provide good fits to the following features: solar luminosity and radius at the solar age, main-sequence width, red-giant and red-supergiant (RSG) positions in the HRD, surface abundances, and rotational velocities. Results. Rotating stellar models predict that about half of the observed WR stars and at least half of the Type Ibc SNe may be produced through the single-star evolution channel. Rotation increases the duration of the WNL and WNC phases, while reducing those of the WNE and WC phases, as was already shown in previous works. Rotation increases the frequency of Type Ic SNe. The upper mass limit for Type II-P SNe is ∼19.0 M for the non rotating models and ∼16.8 M for the rotating ones. Both values agree with observations. Moreover, present rotating models provide a very good fit to the progenitor of SN 2008ax. We discuss future directions of research for further improving the agreement between the models and the observations. We conclude that the mass-loss rates in the WNL and RSG phases are probably underestimated at present. We show that up to an initial mass of 40 M , a surface magnetic field inferior to about 200 G may be sufficient to produce some braking. Much lower values are needed at the red supergiant stage. We suggest that the presence/absence of any magnetic braking effect may play a key role in questions regarding rotation rates of young pulsars and the evolution leading to LGRBs.

Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population

“…We deduce that an average WR phase duration of 0.25 Myr is necessary to sustain our estimated population, assuming a Kroupa IMF and a constant Milky Way star formation rate of 1.9 M⊙yr −1 . This is compatible with the WR phase duration in rotating stellar models at solar metallicity (Georgy et al 2012).…”

“…Taking the Milky Way SFR to be 1.9 M⊙yr −1 (Chomiuk & Povich 2011), adopting a three-part Kroupa IMF (Kroupa & Weidner 2003), and assuming only stars with an initial mass > 25 M⊙ experience a WR phase, our derived population can be reproduced with τWR ≃ 0.25 Myr. This result is broadly consistent with rotating (nonrotating) Geneva models at solar metallicity (Georgy et al 2012), which display τWR = 0.45 Myr (0.006 Myr) at Mi = 32 M⊙ increasing with mass to 0.9 Myr (0.4 Myr) at Mi = 120 M⊙. WR lifetimes as a result of binary evolution at solar metallicity are predicted to span τWR = 0.5 Myr at Mi = 30 M⊙ to 1.0 Myr at 120 M⊙ (Eldridge et al 2008).…”

Fundamental properties of core-collapse supernova and GRB progenitors: predicting the look of massive stars before death

“…The current generation of Geneva evolutionary models Georgy et al 2012) predict that single rotating stars with initial masses (M ini ) in the range 8 M < ∼ M ini < ∼ 17 M end their lives as red supergiant (RSG) stars before a SN event of the type IIP (i.e., with H lines dominating the spectrum and a plateau in the lightcurve). This scenario is supported well by the observations of SN IIP progenitors in New evolution models and model spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A131 pre-explosion images, which have been shown to be RSGs with 8.5 M < ∼ M ini < ∼ 16.5 M ).…”

Evolution and Nucleosynthesis of Massive Stars

“…2) They predict too high rotation for the young pulsars, about two orders of magnitude above what is observed [19,26]. On the other hand meridional currents have the following strong/weak points:…”

“…• Weak points: 1) They predict a too high frequency of long soft GRBs (note that they would explain some GRB's observed to occur at high metallicities) [19,26]. 2) They predict too high rotation for the young pulsars, about two orders of magnitude above what is observed [19,26].…”