MOST1 detects g- and p-modes in the B supergiant HD 163899 (B2 Ib/II)

H. Saio, R. Kuschnig, A. Gautschy, C. Cameron, G. A.H. Walker, J. M. Matthews, D. B. Guenther, A. F.J. Moffat, S. M. Rucinski, D. Sasselov, W. W. Weiss

Research output: Contribution to journalArticle

81 Citations (Scopus)

Abstract

The Microvariability and Oscillations of Stars (MOST) satellite observed the B supergiant HD 163899 (B2 Ib/II) for 37 days as a guide star and detected 48 frequencies ≲ 2.8 cycles day-1 with amplitudes of a few millimagnitudes (mmag) and less. The frequency range embraces g- and p-mode pulsations. It was generally thought that no g-modes are excited in less luminous B supergiants because strong radiative damping is expected in the core. Our theoretical models, however, show that such g-modes are excited in massive post-main-sequence stars, in accordance with these observations. The nonradial pulsations excited in models between 20 M at log T eff ≈ 4.41 and 15 M⊙ at log Teff ≈ 4.36 are roughly consistent with the observed frequency range. Excitation by the Fe bump in opacity is possible because g-modes can be partially reflected at a convective zone associated with the hydrogen-burning shell, which significantly reduces radiative damping in the core. The MOST light curve of HD 163 899 shows that such a reflection of g-modes actually occurs and reveals the existence of a previously unrecognized type of variable, slowly pulsating B supergiants (SPBsg) distinct from α Cyg variables. Such g-modes have great potential for asteroseismology.

Original languageEnglish
Pages (from-to)1111-1118
Number of pages8
JournalAstrophysical Journal
Volume650
Issue number2 I
DOIs
Publication statusPublished - 2006 Oct 20

Keywords

  • Stars: early-type
  • Stars: individual (HD 163899)
  • Stars: oscillations
  • Supergiants

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'MOST<sup>1</sup> detects g- and p-modes in the B supergiant HD 163899 (B2 Ib/II)'. Together they form a unique fingerprint.

  • Cite this

    Saio, H., Kuschnig, R., Gautschy, A., Cameron, C., Walker, G. A. H., Matthews, J. M., Guenther, D. B., Moffat, A. F. J., Rucinski, S. M., Sasselov, D., & Weiss, W. W. (2006). MOST1 detects g- and p-modes in the B supergiant HD 163899 (B2 Ib/II). Astrophysical Journal, 650(2 I), 1111-1118. https://doi.org/10.1086/507409