Asteroseismology based on high time-resolution and high dispersion spectroscopy

2013 Fiscal Year Final Research Report

• Project/Area Number: 23540260
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Astronomy
• Research Institution: The University of Tokyo
• Principal Investigator: SHIBAHASHI Hiromoto 東京大学, 理学(系)研究科(研究院), 教授 (30126081)
• Project Period (FY): 2011 – 2013
• Keywords: 星震学 / 脈動星 / 特異星 / B型輝線星 / 分光観測 / データ解析

Research Abstract

The vertical wavelengths of the oscillations found in roAp stars are so short that the amplitude and phase of the variation of each spectroscopic line are highly dependent on the level of the line profile. We carried out a numerical simulation of line-profile variation by taking account of the finite thickness of the line-forming layer. We demonstrated how effective this treatment is.
Barycentric corrections made to the timing of Kepler observations break the regular time-sampling of the data. A consequence is that Nyquist aliases are split into multiplets that can be identified by their shape. We provided an analytical derivation of the phenomenon, alongside demonstrations with simulated and real Kepler data.
Observations indicate that a circumstellar disk is formed around a Be star while the stellar rotation is below the break-up velocity. I proposed a working hypothesis to explain this mystery by taking account of the effect of leaky waves upon angular momentum transfer.

Research Products

• [Journal Article] Shock Diagnostics in the Pulsating Proto-Subdwarf V652 Herculis (2014)
  • Author(s): Jeffery, C. S., Montañés-Rodríguez, P., Shibahashi, H., Kurtz, D. W., Elkin, V., and Saio, H
  • Journal Title: Astron. Soc. Pacific Conf. Ser Volume: Vol. 481 Pages: 125-131
• [Journal Article] Finding binaries among Kepler pulsating stars from phase modulation of their pulsations (2014)
  • Author(s): Murphy, S. J., Bedding, T. R., Shibahashi, H., Kurtz, D. W., and Kjeldsen, H
  • Journal Title: Monthly Notices Roy. Astron. Soc Volume: (掲載決定済)
  • Peer Reviewed
• [Journal Article] (2013)
  • Author(s): Jeffery, C. S., Shibahashi, H., Kurtz, D. W., Elkin, V., Montañés-Rodríguez, P., and Saio, H
  • Journal Title: Astron. Soc. Pacific Conf. Ser Volume: Vol. 479 Pages: 369-376
• [Journal Article] A Working Hypothesis about the Cause of Be Stars: Episodic Outward Leakage of Low-Frequency Modes Excited by the Iron-Peak κ-Mechanism (2013)
  • Author(s): Ishimatsu, H. and Shibahashi, H
  • Journal Title: Astron. Soc. Pacific Conf. Ser Volume: Vol. 479 Pages: 325-333
• [Journal Article] Super-Nyquist asteroseismology with the Kepler Space Telescope (2013)
  • Author(s): Murphy, S. J., Shibahashi, H., and Kurtz, D. W
  • Journal Title: Monthly Notices Roy. Astron. Soc Volume: Vol. 430, Issue 4 Pages: 2986-2998
  • DOI: 10.1093/mnras/stt105
  • Peer Reviewed
• [Journal Article] FM stars: a Fourier view of pulsating binary stars, a new technique for measuring radial velocities photometrically (2012)
  • Author(s): Shibahashi, H. and Kurtz, D. W
  • Journal Title: Monthly Notices Roy. Astron. Soc Volume: Vol. 422, Issue 1 Pages: 738-752
  • DOI: 10.1111/j.1365-2966.2012.20654.x
  • Peer Reviewed
• [Journal Article] Numerical Simulations of Line-Profile Variation beyond a Single-Surface Approximation for Oscillations in roAp Stars (2012)
  • Author(s): Nomura, T., Naito, J., and Shibahashi, H
  • Journal Title: Publ. Astron. Soc. Japan Volume: Vol. 64, No. 1 Pages: Article No. 9, 18
  • DOI: 10.1093/pasj/64.1.9
  • Peer Reviewed
• [Journal Article] The first evidence for multiple pulsation axes: a new rapidly oscillating Ap star in the Kepler field, KIC 10195926 (2011)
  • Author(s): Kurtz, D. W., Cuhna, M. S., Saio, H., Balona, L. A., Elkin, V. G., Shibahashi, H., Brandao, I. M., Uytterhoeven, K., Frandsen, S., Frimann, S. Hatzes, A. Lueftinger, T. Gruberbauer, M., Kjeldsen, H., Christensen-Dalsgaard, J., and Kawaler, S. D
  • Journal Title: Monthly Notices Roy. Astron. Soc Volume: Vol. 414, Issue 3 Pages: 2550-2566
  • DOI: 10.1111/j.1365-2966.2011.18572.x
  • Peer Reviewed
• [Presentation] スーパーナイキスト星震学 (2014)
  • Author(s): 柴橋博資
  • Organizer: 日本天文学会 2014 年春季年会
  • Place of Presentation: 三鷹市
  • Year and Date: 20140319-22
• [Presentation] A working hypothesis about the cause of Be stars: Episodic outward leakage of low-frequency waves excited by the iron-peak κ-mechanism (2013)
  • Author(s): Shibahashi, H
  • Organizer: IAU Symposium 301
  • Place of Presentation: Wrocraw (Poland)
  • Year and Date: 20130819-23
• [Presentation] Super-Nyquist asteroseismology (2013)
  • Author(s): Shibahashi, H
  • Organizer: Kepler Asteroseismic Science Consortium Sixth Workshop
  • Place of Presentation: Sydney (Australia)
  • Year and Date: 20130623-28
• [Presentation] Be 星の星周円盤の生成 (2012)
  • Author(s): 石松宏幸, 柴橋博資
  • Organizer: 日本天文学会 2012 年秋季年会
  • Place of Presentation: 大分市
  • Year and Date: 20120919-21
• [Presentation] Frequency modulated stars (2012)
  • Author(s): Shibahashi, H
  • Organizer: Kepler Asteroseismic Consortium Fifth Workshop
  • Place of Presentation: Balatonalmádi (Hungary)
  • Year and Date: 20120618-22
• [Presentation] roAp 星におけるスペクトル線プロファイル変動 (2011)
  • Author(s): 内藤純, 柴橋博資
  • Organizer: 日本天文学会 2011 年秋季年会
  • Place of Presentation: 鹿児島市
  • Year and Date: 20110922-24
• [Presentation] Numerical simulations of line-profile variation beyond a single-surface approximation for oscillations in roAp stars (2011)
  • Author(s): Shibahashi, H
  • Organizer: IAU Symposium
  • Place of Presentation: Oxford (UK)
  • Year and Date: 20110918-23
• [Presentation] Traditional approximation for low-frequency modes in rotating stars and a working hypothesis about episodic mass-loss in Be stars (2011)
  • Author(s): Shibahashi, H
  • Organizer: The 20th Stellar Pulsation Conference Series
  • Place of Presentation: Granada (Spain)
  • Year and Date: 20110905-09