2006/06/29 by H. Saio, Hideyuki Saio, R. Kuschnig +13 · 2 citations
Physics and Astronomy · #Amplitude #Asteroseismology #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Atomic physics #Excited state #Light curve #Opacity #Optics #Physics #Radiative transfer #Stars #Stellar, planetary, and galactic studies #Supergiant #astro-ph
paper · pdf · doi:10.1086/507409
published as Astrophys.J.650:1111-1118,2006 · 24 pages, 9 figures, Astrophysical Journal in press
arxiv created 2006/06/29 · openalex publication_date 2006/10/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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 T eff ≈ 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 163899 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.