旋涡星系中恒星形成对旋涡结构的影响

本文利用N体数值模拟方法,讨论了旋涡星系中恒星形成对旋涡结构的维持作用。在假定恒星是在一定密度区域中形成以及恒星诞生率为1.0M_⊙/年的情况下,模拟结果表明,旋涡图象的维持时间是未考虑恒星形成模型的2.3倍。     

恒星演化晚期阶段研究中的流体动力学计算方法

综述了数值模拟恒星演化晚期阶段所使用的流体动力学计算方法和程序等方面的情况以及研究现状。     

恒星内部电荷屏幕对电子俘获反应的影响

本文分析了在恒星环境下，电荷强屏蔽对原子核电子俘获反应的影响，分析中忽略了电荷屏幕对核跃迁矩阵元的影响。作为例子，分别讨论了电荷屏蔽对核素＾３３Ｓ、＾３０Ｐ和＾５７Ｆｅ的电子俘获率的影响。结果表明：在较低温度和较高密度下，由于电荷屏蔽，其电子俘获率相对于无屏蔽情形有明显降低，这可能对恒星晚期演化和超新星爆发理论带来明显的影响。     

自转对恒星物理量的影响

自转本身是恒星的基本物理量之一，同时影响恒星的其它许多物物量，包括对恒星半径、形状和体积的影响；对光度、包指数、谱线轮廓、等值宽度、偏振度等观测量的影响；对引力加速度、元素丰度的影响；对恒星内部结构，如中心压力、温度、密度的影响。这些将会影响到恒星在Ｈ—Ｒ图上的位置，演化路径以及年龄和寿命等。因此，无论是理论模型还是实测研究，对自转快的恒星应该进行自转影响的修正。     

自转对恒星物理量的影响

自转本身是恒星的基本物理量之一，同时影响恒星的其它许多物物量，包括对情理星半径、形状和体积的影响。对光度，色指数、谱线轮廓，先进值宽度，偏振度等观测量的影响；对引力加速度，元素丰度的影响；对恒星内部结构，如中心压力，温度，密度的影响。     

恒星内部的超声速对流区

依传统的局部混合长理论进行了对流包层模型计算,在黄红巨星和超巨星对流区的顶部出现超声速对流的情况,这与局部对流理论本身是不自恰的．文章详细分析了恒星大气超声速对流的成因,并按照星族Ⅰ恒星的演化轨迹,在赫罗图上给出了出现超声速对流的区域．其结果是。在演化过程中, (1)低质量星基本不出现超声速对流; (2)中等质量星的超声速对流主要出现在3．6相似文献   

恒星内部电荷屏蔽对电子俘获反应的影响

本文分析了在恒星环境下，电荷强屏蔽对原子核电子俘获反应的影响，分析中忽略了电荷屏蔽对核跃迁矩阵元的影响．作为例子，分别讨论了电荷屏蔽对核素33S、30P和57Fe的电子俘获率的影响．结果表明：在较低温度和较高密度下，由于电荷屏蔽，其电子俘获率相对于无屏蔽情形有明显降低，这可能对恒星晚期演化和超新星爆发理论带来明显的影响．     

恒星内部电荷屏蔽对β衰变率的影响

针对低能反应和共振跃迁,分析了在恒星内部电荷屏蔽对β衰变率的影响．对共振跃迁的分析是基于核的壳层模型．作为例子,详细计算了电荷屏蔽对56Cr的β衰变的影响．结果表明:在较低温度和高密度下,电荷屏蔽使β衰变率有明显的增加。这对恒星晚期演化和超新星爆发研究可能会有重要的影响。     

OPAL不透明度对恒星结构和演化模型的影响

本文利用国际上最新公布的OPAL不透明度表及相应的化学丰度，计算了三颗不同初始质量的星族互恒星的非守恒演化模型，并和过去长期采用的LAOL不透明度的结果进行详细比较，得出以下主要结论：（1）恒星HR图中的演化轨迹光度降低，主序位置明显向红方向移动；（2）恒星中心H，He燃烧寿命大大延长了；（3）小质量星氢燃烧核和对流核都变小，大、中质量星的中心对流核和燃烧核都有所增大；（4）恒星中心温度－密度关系基本不受影响．     

奇异星壳层塌缩的数值研究

当奇异星表面的电场不足以支撑整个壳层的时候,壳层就有可能全部落入奇异核中.对这一过程的研究,可以为观测上证认奇异星提供一些可能的理论线索.数值计算表明,底部密度为-8.3×1010gcm-3,亦即质量为-3 4×10-6M(?)的壳层在约5.4×10-3s时间内塌缩到奇异核中,可导致一次持续约0.15s的爆发事件.在过程中平均每个重子释放约6.3 MeV的能量,总辐射能则可高达-1046-1047ergs.这可以用来解释宇宙中一些爆发现象.     

一个大质量恒星形成复合体的动力学性质

恒星形成于分子云之中, 分子外向流是恒星形成正在进行的重要动力学特征, 也是研究和认识恒星形成的重要契入点. 利用紫金山天文台青海观测站德令哈13.7m毫米波望远镜, 采用5种分子谱线探针(包括¹²CO、¹³CO、C¹⁸O、HCO$^+$ $J=1-0$和CS $J=2-1$, J为角动量量子数), 对一个包含IRAS 19230+1506、IRAS 19232+1504和G050.3179--00.4186这3个源的大质量恒星形成复合体进行了成图观测研究. 通过对以上分子谱线数据并结合红外波段巡天数据的分析, 在这3个源中首次探测到了分子外向流活动, 并确定了分子外向流的中心驱动源. 最后对这3个源进行了分子外向流相关物理量参数的计算, 分析了这些物理量参数之间的关系, 结果表明分子外向流的性质与中心驱动源的性质息息相关.     

Asynchronous Rotation of a Massive Star in Close Binary Systems

Astrophysics - The problem of asynchronous rotation of massive stars in close binary systems is investigated in this paper. A massive star with twice the sun’s mass, a convective core, and an...     

A Note on the Mixing Length Theory and Massive Star Evolution

1 INTRODUCTIONThe mixing length theory (MLT) for stellar convection originally developed by Vitense(1953, 1958) has been the most popularly used local convection theory in the studies of stellarstructure and evolution. The theory was later modified and revised by many investigators,who suggested some different expressions. In fact, MLT is not a real hydrodynamic theory,rather, it is a simple "ballistic" theory which traces the motion of imaginary convective elements. In reality j stell…     

密近双星子星间的照射吸收对具有椭率子星表面温度的改变

照射吸收引起的子星表面温度不均匀分布是子星包层大气斜压性的原因,同时又 会影响到光变曲线的形态．要了解子星包层大气斜压性形成的详细图景,要计算双星 照射吸收对光变曲线的影响,首先要计算出经过照射吸收后双星表面温度的改变,本 文在最简单的双球模型的基础上,采用椭球－球模型就椭球受球的照射吸收后所改变 的表面温度进行了计算．     

Evidence of Evolution in the Dense Cores in Massive Star Forming Regions

The excitation of H2O masers usually needs very high density gas, hence it can serve as a marker of dense gas in HII region. We selected a sample of H2O maser sources from Plume et al. (four with, and four without detected CS(J = 7-6) emission), and observed them in 13CO(J=1-0) and C18O (J=1-0). C18O (J=1-0) emission was detected only in three of the sources with detected CS(J=7-6) emission. An analysis combined with some data in the literature suggests that these dense cores may be located at different evolutionary stages. Multi-line observation study may provide us clues on the evolution of massive star forming regions and the massive stars themselves.     

Near-Infrared Observations of the Massive Star Forming Region IRAS 23151＋5912

Near-infrared images and K-band spectroscopy of the massive star-forming region IRAS 23151+5912 are presented. The JHK' images reveal an embed-ded infrared cluster associated with infrared nebula, and the H_2 (2.12μm) narrow-band image provides for the first time evidence of outflow activity associated withthe cluster. That the cluster is young can be shown by the high percentage ofinfrared excess sources and the outflow activity. We suggest an age of the clus-ter of ～ 10~6yr. Eight young stars are found in the bright nebular core aroundIRAS 23151+5912. By the color-magnitude diagrams of the cluster, we found fivehigh--mass YSOs and four intermediate-mass YSOs in the cluster. Eight H_2 emissionfeatures are discovered in the region with a scattered and non-axisymmetric distri-bution, indicating the existence of multiple outflows driven by the cluster. DiffuseH_2 emission detected to the north and to the west of the cluster may result fromUV leakage of the cluster. Brγ, H_2, and CIV emission lines are     

Numerical Simulation of Small Perturbation on an Accretion Disk Due to the Collision of a Star with the Disk Near the Black Hole

In this paper, perturbations of an accretion disk by a star orbiting around a black hole are studied. We report on a numerical experiment, which has been carried out by using a parallel-machine code originally developed by Dönmez (2004). An initially steady state accretion disk near a non-rotating (Schwarzschild) black hole interacts with a “star”, modeled as an initially circular region of increased density. Part of the disk is affected by the interaction. In some cases, a gap develops and shock wave propagates through the disk. We follow the evolution for order of one dynamical period and we show how the non-axisymetric density perturbation further evolves and moves downwards where the material of the disk and the star become eventually accreted onto the central body. When the star perturbs the steady state accretion disk, the disk around the black hole is destroyed by the effect of perturbation. The perturbed accretion disk creates a shock wave during the evolution and it loses angular momentum when the gas hits on the shock waves. Colliding gas with the shock wave is the one of the basic mechanism of emitting the X-rays in the accretion disk. The series of supernovae occurring in the inner disk could entirely destroy the disk in that region which leaves a more massive black hole behind, at the center of galaxies.     

大射电望远镜FAST风环境数值模拟研究

500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope,FAST),整体结构处于复杂的喀斯特地貌上,反射面承受风载荷作用,需要进行抗风设计。建立了FAST反射面及其周边山地地形的计算流体动力学(Computational Fluid Dynamics,CFD)计算模型,计算域范围为40 km×10 km×5.5 km。确定了入口风速剖面的基准高度为海拔810 m。计算了不同风向下反射面风压系数分布特征,得出了不利风向。对挡风墙的研究结果表明,挡风墙高度选择的效果优于位置选择。该研究结果可为FAST工程提供抗风设计的初步参考。     

Third Order Effect of Rotation on Stellar Oscillations of a B Star

We aim at investigating the effect of rotation up to the third order in the angular velocity of a star on the p and g modes, based on the formalism developed by Soufi et al. Our ultimate goal is the study of oscillations of β Cephei stars which are often rapidly rotating stars. Our results show that the third-order perturbation formalism presented by Soufi et al. should be corrected for some missing terms and some misprints in the equations. As a first step in our study of β Cephei stars, we quantify by numerical calculations the effect of rotation on the oscillation frequencies of a uniformly rotating zero-age main-sequence star with 12 M<,??>. For an equatorial velocity of 100km s-1, it is found that the second-and third-order corrections for (l, m)=(2, 2), for instance, are of the order of 0.01% of the frequency for radial order n=6 and reaches up to 0.5% for n=14.