### Abstract

We have succeeded in constructing structures of realistic models for rapidly rotating inhomogeneous stars in the nuclear burning stages. The nuclear reaction networks both for CNO cycle and for helium burning have been successfully included in the 2D numerical code. Concerning the equation of state and the opacity, we have used the same ones as used in calculations of spherical stellar structures. The rotation law in our computations covers uniform rotation and differential rotation with rapidly rotating cores. We have computed several equilibrium sequences of massive stars up to models just before the mass begins to shed from the equatorial surface (critical models). We mainly discuss two critical sequences of models: 1)18 M⊙ stars with hydrogen burning cores and 2) 5 M⊙ helium stars with helium burning cores. It is found that the effect of rotation on the structure is similar for both sequences. For uniformly rotating hydrogen burning stars the luminosity decrease is about 6.4% which is consistent with the results obtained by other authors. For models which have the angular momentum distribution concentrated toward the center, we get very flattened shapes of stellar surfaces. Compared with the non-rotating models, decrease of the luminosity is found to be 16% for the critical models if the total angular momentum is less than 10^{53} g cm^{2} s^{-1} and if a toroid-like structure of the density distribution does not appear. On the other hand, decrease of the luminosity becomes significant for stars with the toroid-like structure of the density distribution, i.e. for toroidal distribution of the energy source. It is remarkable that stars whose ratio of the polar radius to the equatorial radius is less than 0.25 have extended envelopes due to a delicate balance between the gravitational force and the centrifugal force.

Original language | English |
---|---|

Pages (from-to) | 177-186 |

Number of pages | 10 |

Journal | Astronomy and Astrophysics |

Volume | 326 |

Issue number | 1 |

Publication status | Published - Dec 1 1997 |

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### All Science Journal Classification (ASJC) codes

- Astronomy and Astrophysics
- Space and Planetary Science

### Cite this

*Astronomy and Astrophysics*,

*326*(1), 177-186.

**Rapidly rotating stars with either H burning or He burning core.** / Shindo, M.; Hashimoto, M.; Eriguchi, Y.; Müller, E.

Research output: Contribution to journal › Article

*Astronomy and Astrophysics*, vol. 326, no. 1, pp. 177-186.

}

TY - JOUR

T1 - Rapidly rotating stars with either H burning or He burning core

AU - Shindo, M.

AU - Hashimoto, M.

AU - Eriguchi, Y.

AU - Müller, E.

PY - 1997/12/1

Y1 - 1997/12/1

N2 - We have succeeded in constructing structures of realistic models for rapidly rotating inhomogeneous stars in the nuclear burning stages. The nuclear reaction networks both for CNO cycle and for helium burning have been successfully included in the 2D numerical code. Concerning the equation of state and the opacity, we have used the same ones as used in calculations of spherical stellar structures. The rotation law in our computations covers uniform rotation and differential rotation with rapidly rotating cores. We have computed several equilibrium sequences of massive stars up to models just before the mass begins to shed from the equatorial surface (critical models). We mainly discuss two critical sequences of models: 1)18 M⊙ stars with hydrogen burning cores and 2) 5 M⊙ helium stars with helium burning cores. It is found that the effect of rotation on the structure is similar for both sequences. For uniformly rotating hydrogen burning stars the luminosity decrease is about 6.4% which is consistent with the results obtained by other authors. For models which have the angular momentum distribution concentrated toward the center, we get very flattened shapes of stellar surfaces. Compared with the non-rotating models, decrease of the luminosity is found to be 16% for the critical models if the total angular momentum is less than 1053 g cm2 s-1 and if a toroid-like structure of the density distribution does not appear. On the other hand, decrease of the luminosity becomes significant for stars with the toroid-like structure of the density distribution, i.e. for toroidal distribution of the energy source. It is remarkable that stars whose ratio of the polar radius to the equatorial radius is less than 0.25 have extended envelopes due to a delicate balance between the gravitational force and the centrifugal force.

AB - We have succeeded in constructing structures of realistic models for rapidly rotating inhomogeneous stars in the nuclear burning stages. The nuclear reaction networks both for CNO cycle and for helium burning have been successfully included in the 2D numerical code. Concerning the equation of state and the opacity, we have used the same ones as used in calculations of spherical stellar structures. The rotation law in our computations covers uniform rotation and differential rotation with rapidly rotating cores. We have computed several equilibrium sequences of massive stars up to models just before the mass begins to shed from the equatorial surface (critical models). We mainly discuss two critical sequences of models: 1)18 M⊙ stars with hydrogen burning cores and 2) 5 M⊙ helium stars with helium burning cores. It is found that the effect of rotation on the structure is similar for both sequences. For uniformly rotating hydrogen burning stars the luminosity decrease is about 6.4% which is consistent with the results obtained by other authors. For models which have the angular momentum distribution concentrated toward the center, we get very flattened shapes of stellar surfaces. Compared with the non-rotating models, decrease of the luminosity is found to be 16% for the critical models if the total angular momentum is less than 1053 g cm2 s-1 and if a toroid-like structure of the density distribution does not appear. On the other hand, decrease of the luminosity becomes significant for stars with the toroid-like structure of the density distribution, i.e. for toroidal distribution of the energy source. It is remarkable that stars whose ratio of the polar radius to the equatorial radius is less than 0.25 have extended envelopes due to a delicate balance between the gravitational force and the centrifugal force.

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M3 - Article

AN - SCOPUS:16944364513

VL - 326

SP - 177

EP - 186

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

IS - 1

ER -