Unified view and interpretation of peculiar pulsation features in roAp stars, RR Lyrae stars, Early-type stars

• Project/Area Number: 11440061
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Astronomy
• Research Institution: The University of Tokyo
• Principal Investigator: SHIBAHASHI Hiromoto Graduate School of Science The University of Tokyo Professor, 大学院・理学系研究科, 教授 (30126081)
• Project Period (FY): 1999 – 2000
• Project Status: Completed (Fiscal Year 2000)
• Budget Amount: ¥5,100,000 (Direct Cost: ¥5,100,000); Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000); Fiscal Year 1999: ¥3,700,000 (Direct Cost: ¥3,700,000)
• Keywords: Stars : Ap stars / Stars : Stars : early-type / Stars : RR Lyrae stars / Stars : pulsation / Stars : magnetic / Blazhko effect / Oblique rotator

Research Abstract

I discuss the oscillation features of the rapidly oscillating Ap stars, the Blazhko effect of the RR Lyrae stars, and β Cephei and interpret them as being a manifestation of a magnetic perturbation to the oscillation eigenfunctions of the stars.
1. The pulsation amplitude of the roAp stars varies synchronously with the magnetic variation, and the amplitude maximum phase coincides with the magnetic maximum phase. I discuss what kind of information is available and outline how it is deduced from the observational data.
2. I discuss the oscillation features of β Cephei, which is a magnetic star in which the magnetic axis seems to be oblique to the rotation axis. I interpret the observed equi-distant fine structure of the frequency spectrum as a manifestation of a magnetic perturbation of an eigenmode, which would be a radial mode in the absence of the magnetic field. Besides these frequency components, I interpret another peak in the frequency spectrum as an independent quadrupole mode. By this mode identification, I deduce the mass, the evolutionary stage, the rotational frequency, the magnetic field strength, and the geometrical configuration of β Cephei.
3. By assuming that RR Lyrae stars have fairly strong dipole magnetic fields with symmetry axis oblique to the rotation axis of the star, I show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, whose symmetry axis coincides with the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent amplitude variation is interpreted as the Blazhko effect in RR Lyrae stars. It is shown that, in the case of off-axis magnetic field, the phase modulation is expected. I list up some theoretical predictions based on this model, which would observationally examine this hypothesis.

Research Products

• [Publications] Sekii,T. et al.: "Local-area Helioseismology by SOT On-board Solar-B"in Proc.of SOHO 10/GONG 2000 Workshop : Helio-and Astero-seismology at the Dawn of the Millennium, eds.A.Wilson (ESA Publication Division. Noordwijk). (in press). (2001)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H.: "What the Helioseismic Results Mean for the Solar Interior"Adv.Space Res.. 24,. 137-145, (1999)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H.: "The Oblique Pulsator Model for the Blazhko Effect in RR Lyrae Stars"in The Impact of Large-Scale Surveys on Pulsating Star Research,IAU Colloq. No.176,eds.L.Szabados & D.W.Kurtz (Astron.Soc.Pacific.San Fransisco). 299-306 (2000)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H.: "Asteroseismology of Magnetic Stars"in Proc.of SOHO 10/GONG 2000 Workshop : Helio-and Astero-seismology at the Dawn of the Millennium,eds.A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H.,& Aerts: "Asteroseismology and Oblique Pulsator Model of β Cephei"Astrophys.J.Letters. 531. L143-L146 (2000)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H. et al.: "Seismic Solar Model : Both of the Radiative Core and the Convective Envelope"Adv.Space Res.. 24. 177-180 (1999)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Shibahashi,H. et al.: "Helioseismic Approach to the Solar Neutrino Problem and Neutrino Oscillations"in Neutrino Oscillations and their Origin,eds.Y.Suzuki,M.Nakahata,M.Shiozawa,& K.Kaneyuki (Universal Academy Press, Tokyo). (in press). (2000)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Takata,M.,& Shibahashi,H.: "The Seismic Solar Model as the State-of-the-Art Model of the Sun"Adv.Space Res.. 24. 181-184 (1999)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Takata,M.,& Shibahashi,H.: "Solar Metal Abundance Inferred from Helioseismology"in Recent Insights into the Physics of the Sun and Heliosphere,-High-lights from SOHO and Other Space Missions-IAU Symp.No.203,eds.P.Brekke,B.Fleck,& J.B.Gurman (Astron.Soc.Pacific,San Fransisco). (in press). (2001)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Watanabe,S.,& Shibahashi,H.: "Low-Z Core Solar Models with Helioseismic Constraints and the Solar Neutrino Problem"in Proc.of SOHO 10/GONG 2000 Workshop : Helio-and Astero-seismology at the Dawn of the Millennium,eds.A.Wilson (ESA Publication Division, Noordwijk),". (in press). (2001)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Sekii, T., Shibahashi, H., Kosovichev, A.G., Duvall, T.L., Jr., Bush, R., and Sherrer, P.H.: "Local-area Helioseismology by SOT On-board Solar-B."in Proc.of SOHO 10/GONG 2000 Workshop : Helio- and Asteroseismology at the Dawn of the Millennium eds. A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H.: "What the Helioseismic Results Mean for the Solar Interior."Adv.Space Res.. 24. 137-145 (1999)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H.: "The Oblique Pulsator Model for the Blazhko Effect in RR Lyrae Stars."in The Impact of Large-Scale Surveys on Pulsating Star Research, IAU Colloq. No.176, eds.L.Szabados & D.W.Kurtz (Astron.Soc.Pacific, San Fransisco). 299-306 (2000)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H.: "Asteroseismology of Magnetic Stars."in Proc.of SOHO 10/GONG 2000 Workshop : Helio- and Asteroseismology at the Dawn of the Millennium eds.A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H., & Aerts, C.: "Asteroseismology and Oblique Pulsator Model of β Cephei."Astrophys.J.Letters. 531. L143-L146 (2000)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H., Hiremath, K.M., & Takata, M.: "Seismic Solar Model : Both of the Radiative Core and the Convective Envelope."Adv.Space Res.. 24. 177-180 (1999)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Shibahashi, H., Hosogai, M., & Takata, M.: "Helioseismic Approach to the Solar Neutrino Problem and Neutrino Oscillations."in Neutrino Oscillations and their Origin, eds.Y.Suzuki, M.Nakahata, M.Shiozawa, & K.Kaneyuki (Universal Academy Press, Tokyo). (in press). (2000)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Takata, M., & Shibahashi, H.: "The Seismic Solar Model as the State-of-the-Art Model of the Sun."Adv.Space Res.. 24. 181-184 (1999)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Takata, M., & Shibahashi, H.: "Solar Metal Abundance Inferred from Helioseismology."in Recent Insights into the Physics of the Sun and Heliosphere, -Highlights from SOHO and Other Space Missions-, IAU Symp.No.203, eds.P.Brekke, B.Fleck, & J.B.Gurman (Astron.Soc.Pacific, San Fransisco). (in press). (2001)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Watanabe, S., & Shibahashi, H.: "Low-Z Core Solar Models with Helioseismic Constraints and the Solar Neutrino Problem."in Proc.of SOHO 10/GONG 2000 Workshop : Helio- and Asteroseismology at the Dawn of the Millennium eds. A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
  • Description: 「研究成果報告書概要(欧文)」より
• [Publications] Sekii,T. et al.: "Local-area Helioseismology by SOT On-board Solar-B"in Proc.of SOHO 10/GONG 2000 Workshop : Helio- and Asteroseismology at the Dawn of the Millennium, eds.A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
• [Publications] Shibahashi,H.: "The Oblique Pulsator Model for the Blazhko Effect in RR Lyrae Stars"in The Impact of Large-Scale Surveys on Pulsating Star Research, IAU Colloq.No.176, eds.L.Szabados & D.W.Kurtz (Astron.Soc.Pacific, San Fransisco). 299-306 (2000)
• [Publications] Shibahashi,H.: "Asteroseismology of Magnetic Stars"in Proc.of SOHO 10/GONG 2000 Workshop : Helio- and Asteroseismology at the Dawn of the Millennium, eds.A.Wilson (ESA Publication Division, Noordwijk). (in press). (2001)
• [Publications] Shibahashi,H.,& Aerts,C.: "Asteroseismology and Oblique Pulsator Model of β Cephei"Astrophys.J.Letters. 531. L143-L146 (2000)
• [Publications] Shibahashi,H. et al.: "Helioseismic Approach to the Solar Neutrino Problem and Neutrino Oscillations"in Neutrino Oscillations and their Origin, eds.Y.Suzuki,M.Nakahata,M.Shiozawa,& K.Kaneyuki (Universal Academy Press, Tokyo). 215-226 (2000)
• [Publications] Takata,M.,& Shibahashi,H.: "Solar Metal Abundance Inferred from Helioseismology"in Recent Insights into the Physics of the Sun and Heliosphere, -High- lights from SOHO and Other Space Missions - IAU Symp.No.203, eds.P.Brekke,B.Fleck, & J.B.Gurman (Astron.Soc.Pacific.San Fransisco). (in press). (2001)
• [Publications] Watanabe,S.,& Shibahashi,H.: "Low-Z Core Solar Models with Helioseismic Constraints and the Solar Neutrino Problem"in Proc.of SOHO 10/GONG 2000 Workshop : Helio-and Asteroseismology at the Dawn of the Millennium, eds.A.Wilson (ESA Publication Division, Noordwijk),". (in press). (2001)
• [Publications] Shibahashi,H.: "What the Helioseismic Results Mean for the Solar Interior"Adv.Space.Res.. 24. 137-145 (1999)
• [Publications] Shibahashi,H.et al.: "Seismic Solar Model : Both of the Radiative Core and the Convective Envelope"Adv.Space.Res.. 24. 177-180 (1999)
• [Publications] Takata,M.,& Shibahashi,H.: "The Seismic Solar Model as the State-of-the-Art Model of the Sun"Adv.Space.Res.. 24. 181-184 (1999)
• [Publications] Shibahashi,H.,& Aerts,C.: "Asteroseismology and Oblique Pulsator Model of $\beta$ Cephei"Astrophys.J.Letters. (in press). (2000)
• [Publications] Shibahashi,H.: "The Oblique Pulsator Model for the Blazhko Effect in RR Lyrae Stars"The Impact of Large-Scale Surveys on Pulsating Star Research,IAU Colloq.No.176,eds.L.Szabados & D.W.Kurtz (Astron.Soc.Pacific,San Fransisco). (in press). (2000)