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Nonradial Oscilations of Rapidly Rotating Stars

Research Project

Project/Area Number 01540213
Research Category

Grant-in-Aid for General Scientific Research (C)

Allocation TypeSingle-year Grants
Research Field Astronomy
Research InstitutionTohoku University (1990)
The University of Tokyo (1989)

Principal Investigator

SAIO Hideyuki  Tohoku University, Faculty of Science, Associate Professor, 理学部, 助教授 (10162174)

Project Period (FY) 1989 – 1990
Project Status Completed (Fiscal Year 1990)
Budget Amount *help
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1990: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
KeywordsStellar Pulsation / Stellar Nonradial Oscillation / Stellar Evolution / Stellar Rotation / Jupiter / Excretion Disk
Research Abstract

In this research project the following results have been obtained :
(1) For rapidly rotating early type stars, we have calculated line profile variations caused by the velocity and temperature variations originated from low-frequency nonradial oscillations. Such low-frequency oscillations are expected to be excited in rotating massive main-sequency stars. The calculated line-profile variations qualitatively agree with those of observed for rapidly rotating early-type stars. This result supports the idea that the theoretically predicted low-frequency oscillations originated from the rotating convective core are responsible for variations observed in early-type stars.
(2) We have investigated, by considering the oscillation energy, the properties of low frequency nonradial oscillations whose excitation we shown numerically in our previous work. We have found that there exist oscillations with negative energy in a convective region. When one of the oscillations with negative energy is in resonance with an ordinary oscillation mode with positive energy, energy flows from the former to the latter to form an overstable coupled oscillation. This mechanism explains nicely the previously obtained numerical results.
(3) We have shown that the same mechanism mentioned above can also works in the envelope of Jupiter. We suggested that low-frequency oscillations excited in this way correspond to the recently osberved very slow global oscillations in the Jovian atmosphere.
(4) When there exist non-axisymmetric oscillations in a star, re-distribution of angular momentum of the matter occurs. If the angular momentum is transferred from the core region to the surface, the matter around the equator may be expelled due to the excess centrifugal force to form an excretion disk. We have calculated the structure of the excretion disk to compare with the observationally expected disks around Be stars.

Report

(3 results)
  • 1990 Annual Research Report   Final Research Report Summary
  • 1989 Annual Research Report
  • Research Products

    (18 results)

All Other

All Publications (18 results)

  • [Publications] 李 宇〓: "Line prefile variations caused by lowーfreguency nonradial pulsations of rapiting stars" Astrophysical Journal. 349. 570-579 (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 李 宇〓: "Energy of oscillatian:The role of negative enegy mode in overstable nonradial oscillations of rotating stars" Aslrophysical Journal. 360. 590-603 (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 斉尾 英行: "Lowーfreguency oscilatiens of rotating mossive stars" Lecture Notes in Physics. 367. 453-456 (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 李 宇〓: "Excitation meihanism of very slow oscillations of the Jovian atmosphere" Astrophysical Journal(Letters). 359. 29-32 (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 斉尾 英行: "Pulsations of hydregenーdeficient stars" Astronomical Society of the Pacific Conference series. 11. 557-567 (1990)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 李 宇〓: "Viscaus excvetion disks around Be stars" Monthly Notices Royal Astronomical Society. (1991)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Lee, U. and Saio, H: "Line profile variations caused by low-frequency nonradial pulsations of rapidly rotating stars" Astrophys. J.349. 570-579 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Lee, U., and Saio, H: "Energy of oscillation : The role of negative energy mode in overstable nonradial oscillations of rotating stars" Astrophys, J.360. 590-603 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Saio, H., and Lee, U: "Low-frequency oscillations of rotating massive stars" Lecture Notes in Physics. 367. 453-456 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Lee, U., and Saio, H: "Excitation mechanism of very slow oscillations of the Jovian atmosphere" Astrophys. J. (Letters). 359. 29-32 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Saio, H: "Pulsations of hydrogen-deficient stars" Astronomical Society of the Pacific Conference Series. 11. 557-567 (1990)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] Lee, U., Saio, H, and Osaki, Y. 1991: "Viscous excretion disks around Be stars" Monthly Notices Roy. Astron. Soc.(1991)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1990 Final Research Report Summary
  • [Publications] 李 宇〓: "Excitation Mechanism of Very Slow Oscillations of the Jovian Atmosphere" The Astrophysical Jaumal. 359. L29-L32 (1990)

    • Related Report
      1990 Annual Research Report
  • [Publications] 李 宇〓: "Viscous excretion disks around Be stays" Monthly Notices Royal astronomical Society. (1991)

    • Related Report
      1990 Annual Research Report
  • [Publications] 斉尾 英行: "Pulsations of Hydrogenーdeficieit Stars" Astronomical Society of the Pacific Conference Series. 11. 557-565 (1990)

    • Related Report
      1990 Annual Research Report
  • [Publications] 李宇〓: "Line Profile Variations Caused by Low-Frequency Nonradial Pulsations of Rapidly Rotaing Stars" The Astrophysical Journal. 349. 570-579 (1990)

    • Related Report
      1989 Annual Research Report
  • [Publications] 李宇〓: "Energy of Oscillation:The Role of Negative Energy Mode in Oberstable Nonradial Oscillations of Rotating Stars" The Astrophysical Journal. (1990)

    • Related Report
      1989 Annual Research Report
  • [Publications] 齋尾英行: "Low-frequency Oscillations of Rotating Massive Stars" Lecture Notes in Physics. (1990)

    • Related Report
      1989 Annual Research Report

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Published: 1989-04-01   Modified: 2016-04-21  

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