Lines formed in rotating and expanding atmospheres     

A. Peraiah 《Journal of Astrophysics and Astronomy》1980,1(1):17-23

Spectral lines formed in a rotating and expanding atmosphere have been computed in the frame of the observer at infinity. Two kinds of velocity laws are employed: (i) a uniform radial velocity of the gas and (ii) velocity increasing with radius (i.e. velocity gradients). The atmosphere has been assumed to be rotating with constant velocity. We have considered maximum radial and rotational velocities to be 10 and 3 mean thermal units respectively in an atmosphere whose geometrical thickness is 10 times the stellar radius. The total radial optical depth at line centre is taken to be about 100. In all cases, Doppler profile and a source function which is varying as 1/r ² have been used. Generally, the lines are broadened when rotation is introduced. However, when radial motion is also present, broadening becomes asymmetric and the red emission and blue absorption are enhanced.  相似文献   

On the synthesis of a large geomagnetic array from small overlapping arrays     

G. D. Egbert 《Geophysical Journal International》1991,106(1):37-51

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Centre shift of the Raman scattered He iiλ 4850 in the symbiotic star V1016 Cygni     

Yang-Chan Jung  Hee-Won Lee 《Monthly notices of the Royal Astronomical Society》2004,355(1):221-228

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云南天文台太阳望远镜光学系统的光学传递函数检验     

李如凤  张霄宇  陈学昆 《天文研究与技术》2004,1(2):160-162

摘要：给出了太阳光谱望远镜光学系统成像质量的测定方法．以及给出了我们用星光作为目标来测定望远镜光学系统传递函数时必须考虑的条件和理论基础。实测结果给出望远镜空间分辨率的上限为0．6“，95％光能集中度在1．2“以内。  相似文献   

基于轨道改正的卫星电视时间传递   总被引：1，自引：0，他引：1  

杨旭海  王晓晗  李志刚  张继荣  李伟超  梁双有 《时间频率学报》2006,29(2):100-106

利用在模拟卫星电视信号中插入的时间信息可实现时间传递,但由于它常采用固定的卫星位置,限制了时间传递精度。为此,研究了基于轨道改正的卫星电视时间传递方法,并给出了在轨道改正的基础上实现单向和共视时间传递的计算公式。将该方法应用于我国的模拟卫星电视时间传递中,计算了从中央电视台到国家授时中心的单向时间传递结果。  相似文献   

The scattering of Lyman-series photons in the intergalactic medium     

Steven R. Furlanetto  Jonathan R. Pritchard 《Monthly notices of the Royal Astronomical Society》2006,372(3):1093-1103

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Hot Subdwarfs in Precataclysmic Binaries     

Vladislav Pustynski  Izold Pustylnik 《Astrophysics and Space Science》2006,304(1-4):267-270

We present a brief review of the recent results in modeling physical processes in strongly irradiated atmospheres of unevolved companions in precataclysmic binary systems (PCB) and their light curves. Constraints on physical parameters of the hot sdws primaries, thermal instability in upper irradiated atmosphere, monochromatic albedos, the deficit of the total emergent flux compared to the incoming flux from hot sdw primary are briefly discussed.  相似文献   

Solar flux in Saturn's atmosphere: Penetration and heating rates in the aerosol and cloud layers     

S. Pérez-Hoyos  A. Sánchez-Lavega 《Icarus》2006,180(2):368-378

In this work, we describe an analysis of the internal solar radiation fields in Saturn's atmosphere. The aim of this paper is to study how the solar radiation flux in optical wavelengths (0.25-1.0 μm) is attenuated, primarily by the effect of the aerosols located close to the tropopause level, retrieving also the corresponding solar heating rates. We use a doubling-adding method and previous results on the vertical cloud and haze structure of Saturn's atmosphere. Our study shows that the maximum penetration level (∼250 mbar) for these wavelengths is substantially higher than previously expected because of the huge optical thickness of the tropospheric haze described in all vertical cloud structure models. We compare our results with previous estimates and parameterizations for seasonal climate models and propose a new approach for future models, with an intense and concentrated heating rate close to the top level of the tropospheric haze. Given that our spectral range accounts for about the 70% of the total solar flux, and using previous estimates for the penetration levels of infrared radiation in Saturn's atmosphere, we conclude solar radiation effect is negligible at levels below 600 mbar. This result is fundamental for understanding the role of solar radiation in the general atmospheric circulation of Saturn.  相似文献   

Deuterium chemistry and airglow in the jovian thermosphere     

C.D. Parkinson  J.C. McConnell  A.Y.-T. Lee  E. Griffioen 《Icarus》2006,183(2):451-470

We present a detailed study of the distribution of key deuterated species (viz., atomic D and HD) and the associated deuterium Lyman-α airglow in the jovian thermosphere. The reactions that appear to govern the abundances of these deuterated species are used in conjunction with C₂-chemistry in a 1-D photochemical-diffusion model. While the D abundance is mainly sensitive to H densities and the vibrational temperature profile, the D vertical distribution also depends on other parameters such as eddy mixing and the uncertain values of some of the reaction rate constants. We consider different scenarios by varying several parameters controlling the D distribution in the thermosphere. A radiative transfer model with coupling of the H and D Lyman-α lines is employed to obtain line profiles and total intensities at disk center for these scenarios. This allows a comparison of the impact of various parameters on the jovian D Lyman-α emission. A consequence of these chemical processes in the jovian thermosphere is the formation of CH₂D, CH₃D, and C₂H₅D, and other deuterated species. We also discuss the source of these deuterated hydrocarbons and their abundance. We find that HD vibrational chemistry impacts D in the thermosphere, CH₃D and C₂H₅D are vibrationally enhanced in the thermosphere, and variations in abundance of CH₃D and C₂H₅D in the thermosphere may reflect dynamical activity (i.e., Kh) in the jovian upper atmosphere. An observing program dedicated to providing such measurements of these testable phenomena would provide further insight into the synergistic coupling between chemistry, energetics and airglow in the jovian upper atmosphere.  相似文献   

Atmosphere models of magnetized neutron stars: QED effects, radiation spectra and polarization signals     

M. van Adelsberg  D. Lai 《Monthly notices of the Royal Astronomical Society》2006,373(4):1495-1522

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