慢脉动B型星（英语：Slowly Pulsating B-type，缩写：SPB）是HR图上的主序星。它们的振荡是高阶、低阶g模，可以用来探测对流核外边界附近辐射区的结构，并限制恒星内部的化学混合。在SPB星中，周期间隔随周期而周期性变化。它被认为是对流核以外的化学成分梯度的标志。通过理论计算，我们发现周期间距的变化频率（$f_{ΔP}$）与浮力半径上的$μ$梯度区宽度（$Λ_μ$）有$f_{ΔP}\sim0.5Λ_μ$关系。这表明变化频率$f_{ΔP}$对中心氢质量分数$X_{\rm C}$敏感（即，进化论）。最后，我们发现，利用周期间隔的变化频率$f_{ΔP}$和周期间隔的平均值$\langleΔP\rangle$可以构造一个新的类C-D图（$f_{ΔP}$ vs. $\langleΔP\rangle$），该图可以用来粗略地判定恒星的演化阶段和近似地确定恒星质量。
英文摘要：
The Slowly Pulsating B-type (SPB) stars are the upper main-sequence stars on the HR diagram. Their oscillations are high-order, low-degree g-mode and can be used to probe the structure of the radiative zone where is near the outer boundary of the convective core and constrain the chemical mixing in stellar interiors. In SPB stars, the period spacing periodically varies with periods. It has regarded as a signature of the chemical composition gradient beyond the convective core. Based on theoretical calculations, we find that the variation frequency of the period spacings ($f_{ΔP}$) is related to the width of the $μ$-gradient region on the buoyancy radius ($Λ_μ$) with the relation of $f_{ΔP}\sim0.5Λ_μ$. This indicates that the variation frequency $f_{ΔP}$ is sensitive to the central hydrogen mass fraction $X_{\rm C}$ (i.e., the evolutionary status). Finally, we find that the variation frequency $f_{ΔP}$ and the means of the period spacings $\langleΔP\rangle$ can be used to construct a new C-D-like diagram ($f_{ΔP}$ vs. $\langleΔP\rangle$) which can be used to roughly decide the stellar evolutionary stages and to approximately determine stellar mass for SPB stars.
KIC8264293 is a fast rotating B-type pulsator observed by Kepler satellite. Its photometric variability is mainly due to pulsations in high-order g modes. Besides, we detected a weak H$α$ emission. Thus, the second source of variability is the fluctuation in a disk around the star. The pulsational spectrum of KIC8264293 reveals a frequency grouping and period spacing pattern. Here, we present the thorough seismic analysis of the star based on these features. Taking into account the position of the star in the HR diagram and fitting the 14 frequencies that form the period spacing we constrain t…
Inferring main-sequence stage and buoyancy-glitch amplitudes from Fourier spectra of gravity-mode period spacings: Ensemble Analysis of 26 Slowly Pulsating B Stars
Context. Slowly pulsating B (SPB) stars are main-sequence multi-periodic oscillators that display non-radial gravity modes. For a fraction of these pulsators, 4-year photometric light curves obtained with the Kepler space telescope reveal period spacing patterns from which their internal rotation and mixing can be inferred. In this inference, any direct resonant mode coupling has usually been ignored so far. Aims. We re-analysed the light curves of a sample of 38 known Kepler SPB stars. For 26 of those, the internal structure, including rotation and mixing, was recently inferred from their dip…
The relation of period spacing ($ΔP$) versus period ($P$) of dipole prograde g modes is known to be useful to measure rotation rates in the g-mode cavity of rapidly rotating $γ$ Dor and slowly pulsating B (SPB) stars. In a rapidly rotating star, an inertial mode in the convective core can resonantly couple with g modes propagative in the surrounding radiative region. The resonant coupling causes a dip in the $P$-$ΔP$ relation, distinct from the modulations due to the chemical composition gradient. Such a resonance dip in $ΔP$ of prograde dipole g modes appears around a frequency corresponding …
Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the HR diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs, and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sampl…
