共查询到20条相似文献，搜索用时 15 毫秒
1.
本文对太阳型大气(见表1)计算了以一个氢粒子为单位的罗斯兰平均不透明度_R(T,lgP_e)(见表2)。本文考虑的连续不透明度源如下:(1)H~-,HⅠ,H_2~-,H_2~ ,He~-,HeⅠ,HeⅡ,CⅠ,CⅡ,CⅢ,NⅠ,NⅡ,NⅢ,OⅠ,OⅡ,NaⅠ,MgⅠ,MgⅡ,AlⅠ,AlⅡ,siⅠ,SiⅡ,ClⅠ,KⅠ,CaⅡ的吸收。(2)HⅠ,HeⅠ,CⅠ,NⅠ,OⅠ,H_z的瑞利散射。(3)自由电子的汤姆逊散射。 相似文献
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Bo Liu Hong-Yan Zhou Xin-Wen Shu Shao-Hua Zhang Tuo Ji Xiang Pan Peng Jiang 《天文和天体物理学研究(英文版)》2021,(3):133-148
We report on the discovery of unusual broad absorption lines(BALs)in the bright quasar SDSS J075133.35+134548.3 at z~1,using archival and newly obtained optical and NIR spectroscopic data.The BALs are detected reliably in HeⅠ*λ3889,HeⅠ*λ10830 and tentatively in AlⅢ,MgⅡ.These BALs show complex velocity structures consisting of two major components:a high-velocity component(HV),with a blueshifted velocity range ofΔvHV~9300--3500 km s-1,which can be reliably detected in HeⅠ*λ10830,and tentatively in AlⅢand MgⅡ,whereas it is undetectable in HeⅠ*λ3889;and a low-velocity component(LV),withΔvLV~3500--1800 km s-1,is only detected in HeⅠ*λ3889 and HeⅠ*λ10830.With the BALs from different ions,the HV outflowing gas can be constrained to have a density of nH~1010.3-1011.4 cm-3,a column density of NH~1021 cm-2and an ionization parameter of U~10-1.83-10-1.72;inferring a distance of RHV~0.5 pc from the central continuum source with a monochromatic luminosityλLλ(5100)=7.0×1045erg s-1at 5100 A.This distance is remarkably similar to that of the normal broad line region(BLR)estimated from reverberation experiments,suggesting association of the BLR and the HV BAL outflowing gas.Interestingly,a blueshifted component is also detected in AlⅢand MgⅡbroad emission lines(BELs),and the AlⅢ/MgⅡof such a BEL component can be reproduced by the physical parameters inferred from the HV BAL gas.The LV BAL gas likely has a larger column density,a higher ionization level and hence a smaller distance than the HV BAL gas.Further spectroscopy with a high S/N ratio and broader wavelength coverage is needed to confirm this to shed new light on the possible connection between BALs and BELs. 相似文献
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基于Weinberg-Salam理论,考虑Coulomb效应对连续态电子气体的影响,对恒星演化晚期核素12C、16O、20Ne、24Mg、28Si和56Fe在完全电离环境下的K壳层连续态自由电子俘获过程的中微子能量损失进行了讨论.根据Beaudet、Petrosian和Salpeter (BPS)的方法所得结果与我们的结果进行了比较.结果表明:相对较高温度环境(如T9=0.1和T9=1.T9是以109 K为单位的温度),两种结果符合很好;而低温环境(如T9=0.01和T9=0.001)核素16O、20Ne、24Mg和28Si的中微子能量损失,BPS的结果比我们的结果高10～70倍,对核素12C甚至高出2个数量级.我们的研究可能对恒星演化晚期尤其是白矮星核坍塌到相对低温和中等密度阶段冷却机制的研究具有重要意义. 相似文献
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低质量AGB星He壳层内重元素核合成 总被引：1，自引：0，他引：1
以^13C（α,n)^16O和^22Ne(α，n）^25Mg作为双脉冲中子源，对于星族Ⅰ低质量AGB星，采用无分叉s-过程反应通道，结合最新恒星深化的计算结果，在各物理参量合理取值范围内，计算了He壳层内重元素核合成。结果表明，渐近分布时所需的脉冲数N0的范围是6－16个，渐近分布达到后，He壳层内重元素的丰度仅与平均中子辐照量τ0有关。与低质量AGB星相应的平均中子辐照量范围是τ0=0.15-1.0mb^-1。 相似文献
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刘汝良 《中国天文和天体物理学报》1983,(2)
利用50个Ⅰ型Seyfert星系的L(H_β)、H_β谱线的零强度宽(FWZI),以及假设吸积物质流模型,求出它们核的质量、热光度和临界光度(Eddington 光度)。发现这样会构成低红移QSO-Ⅰ型Seyfert-Ⅱ型Seyfert的星系核质量分布的序列(图1),Ⅰ型和Ⅱ型Seyfert星系的热光度与临界光度的比值的直方图,也有一个较大的重叠(图2)。再用讫今有的38个Ⅰ型Seyfert星系的X射线光度资料进行统计分析,得到 L_(x(2-10keV))∝M,L_(x(2-10keV))∝(FWZI)~2,利用球吸积模型对结果进行简单的讨论。 相似文献
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本文利用势垒穿透模型计算重离子融合反应截面,我们发现理论计算结果同现有的实验数据符合得相当好。在此基础上,对~(12)C+~(12)C,~(12)C+~(14)N,~(12)C+~(16)O,~(14)N+~(14)N,~(14)N+~(16)O和~(16)O+~(16)O六种融合反应,在T_9=-0.1—5.0温度范内数值计算了这些热核反应率,并给出了它们随温度变化的近似解析表达式.对~(12)C+~(12)C,~(12)C+~(16)O和~(16)O+~(16)O这三种热核反应率,我们的新结果明显地低于Caughlan等人在1985年的列表值,特别是~(16)O+~(16)O的热核反应率比文[21中值低7—20倍,这将对整个大质量恒星的演化、超新星爆发以及核合成带来较大的影响,本文简略地讨论了这些影响. 相似文献
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Using data from Millimetre Astronomy Legacy Team Survey at 90 GHz(MALT90), we present a molecular line study of a sample of APEX Telescope Large Area Survey of the Galaxy(ATLASGAL) clumps. Twelve emission lines have been detected in all. We found that in most sources,emissions of HC_3 N, HN~(13) C, CH_3 CN, HNCO and Si O show more compact distributions than those of HCO~+, HNC, HCN and N_2 H~+. By comparing with other molecular lines, we found that the abundance of HNCO(χ(HNCO)) correlates well with other species such as HC_3N, HNC, C_2H, H~(13) CO~+and N_2 H~+. Previous studies indicate the HNCO abundance could be enhanced by shocks. However, in this study, we find the abundance of HNCO does not correlate well with that of Si O, which is also a good tracer of shocks. We suggest this may be because HNCO and Si O trace different parts of shocks.Our analysis indicates that the velocity of a shock traced by HNCO tends to be lower than that traced by Si O. In the low-velocity shocks traced by HNCO, the HNCO abundance increases faster than that of Si O. While in the relatively high-velocity shocks traced by Si O, the Si O abundance increases faster than that of HNCO. We suggest that in the infrared dark cloud MSXDC G331.71~+00.59, high-velocity shocks are destroying the molecule HNCO. 相似文献
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《天文学报》1958,(1)
I序鱿!底片髓数星名数测畴刻(U .T.)叹2.石。19石0级测一}一一}—}{、、:!童家宫官春春家家家春家官家春春家家春家家洪童春春童童洪童童童蹼家家N 825N 827N 828N 841T 1203T 1204T 1206T 1207N 836T 1208N 839N 851N 859T 1209T 1210N 867N 875T 1246N 884N 885T 1251T 1252T 1253T 1254T 1255T 1256T 1257T 1258T 1259T 1260T 1261N 888N 889寸W 11·tanen(1956C)J Wirtanen(1956C)沙W irtanen(1956C)沙W irtanen(1956C)沙Mrkos(1957d)沙Mrkos(1957d)沙Mrkos(1957d)沙Mrkos(1957d)沙Mrkos(1957d)沙Mrko吕(1957d)J … 相似文献
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《天文和天体物理学研究(英文版)》2017,(6)
The mass-radius relations for white dwarfs are investigated by solving the Newtonian as well as Tolman-Oppenheimer-Volkoff(TOV) equations for hydrostatic equilibrium assuming the electron gas to be non-interacting.We find that the Newtonian limiting mass of 1.4562 M⊙is modified to 1.4166 M⊙in the general relativistic case for 4/2He(and(12)/6C) white dwarfs.Using the same general relativistic treatment,the critical mass for 56/26 Fe white dwarfs is obtained as 1.2230 M⊙.In addition,departure from the ideal degenerate equation of state(EoS) is accounted for by considering Salpeter's Eo S along with the TOV equation,yielding slightly lower values for the critical masses,namely 1.4081 M⊙for 4/2He,1.3916 M⊙for 12/6C and 1.1565 M⊙for 56/26 Fe white dwarfs.We also compare the critical densities for gravitational instability with the neutronization threshold densities to find that42 He and126C white dwarfs are stable against neutronization with the critical values of 1.4081 M⊙and 1.3916 M⊙,respectively.However,the critical masses for 16/8 O,20/10Ne,24/12 Mg,28/14Si,32/16 S and 56/26Fe white dwarfs are lower due to neutronization.Corresponding to their central densities for neutronization thresholds,we obtain their maximum stable masses due to neutronization by solving the TOV equation coupled with the Salpeter EoS. 相似文献
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《天文学进展》2019,(4)
近轨道~①系外行星受到其宿主恒星强烈的X射线和极紫外(X-ray and Extreme Ultraviolet,XUV)辐射。恒星辐射可能会使富气体行星的气体摆脱行星的引力束缚而逃逸到行星的洛希瓣外。随着XUV辐射的增大,行星的大气逃逸可由较缓和的金斯逃逸变为剧烈的流体动力学逃逸。随着空间望远镜和地面望远镜的发展,在一些行星周围发现了膨胀的H,He,C,O,Na和Mg等元素的大气。行星大气研究从最初的紫外波段探测,已经发展到光学波段和近红外波段的探测。理论上,系外行星大气逃逸的流体动力学模型也已相继建立起来。这些模型涉及到行星大气的光化学、恒星风与行星风的相互作用、恒星辐射压以及行星磁场等方面。然而,一个包含所有过程的复杂模型还有待建立。 相似文献
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本文利用紫金山天文台光谱仪加配太阳像和底片同时移动的同步装置,在底片盒前加可以调节的狭缝,旋转光栅,扫描太阳单色像,得到氢 H_α(λ6563)、氢 H_σ(λ4202)、钠 D_2(λ5896)、氦 H_el(λ5876)(即D_线)、铁 FeⅠ(λ6302A)、钙 C_aⅡK(λ3934)等谱线以及连续光潜区的太阳单色像。从单色像照片上可以看出不同谱线单色像有明显的不同。 相似文献
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本文评述了1968年发现天体H_2O分子谱线以来其观测和研究的进展。内容包括(1)天体H_2O脉泽和正常H_2O分子的观测特征;(2)在恒星早期和晚期演化过程中H_2O分子所起的作用和它们可能的状态;(3)利用H_2O分子谱线的观测,研究晚型星拱星包层结构和速度流场、恒星质量损失率以及恒星早期演化过程中的分子云能量平衡等理论研究成果;(4)H_2O脉泽时变特征的观测和研究;(5)银河系天体H_2O(6_(16)-5_(23))脉泽源巡视和H_2O脉泽源星表以及河外H_2O脉泽源的探测。 相似文献
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Eijiro Hiei 《中国天文和天体物理学报》2004,4(4):377-389
After surveying the spectra of 39 prominences observed by the Multichannel Infrared Solar Spectrograph at Purple Mountain Observatory and the 25 cm coronagraph at the Norikura Solar Observatory, we found that about 28% of them show small spatial scale (6"- 8") and short time scale (tens of seconds to a few minutes), unusual large broadening and large shift velocities in spectral lines including Hα, Hβ, Hε, Ca Ⅱ H, Ca Ⅱ K, Ca2Ⅱ 8542 A, He Ⅰ D3 and HeⅠ 10830 A. We present in detail two typical events observed respectively on 2002 May 27 and 1981 August 2. The full-width at half maximum of the widest profile of the 2001 prominence is 1.8 A for Ha and 2.9 A for He I 10830 A, while that of the 1981 prominence is 5.3 A for Hβ, 3.6 A for Ca Ⅱ K, 4.0 A for Ca Ⅱ H and 2.8 A for He Ⅰ D3. Such broadenings generally occur at a level of several-thousand kilometres above the chromosphere. Further, most of these prominences manifest a rotation of (0.4-1.35) ×10-2 rad s-1 pointing to the Sun and large line 相似文献
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Markarian 478是典型的窄线赛弗特I星系之一。本文展示了在 2 0 0 1年 1月利用远紫外光谱探测卫星 (FUSE)观测到的Markarian 478的远紫外光谱。我们的光谱覆盖了 91 5Å ;— 1 1 85Å的波长范围 ,分辨率约为 2 0km/s。我们在连续谱上探测到OⅥλλ1 0 3 2 ,1 0 3 8、NⅢλ989和CⅢλ977强发射线。在高电离双线OⅥ以及Lyβ的蓝端线翼上出现了成协吸收线 ,而在NⅢ和CⅢ发射线上没有出现内禀吸收线。这些吸收线被分解成 5个动力学成分 ,它们相对于系统红移zem=0 .0 774的静止坐标系速度覆盖了从 -2 3 0 0～ 3 70km/s的范围 相似文献
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《天文和天体物理学研究(英文版)》2017,(2)
We present high spatial resolution X-ray spectroscopy of Tycho's supernova remnant(SNR)using observational data from Chandra. The whole remnant was divided into 26 × 27 regions, with each of them covering 20′′× 20′′. We selected 536 pixels with enough events to generate spectra and fit them with an absorbed two component non-equilibrium ionization model. We obtained maps of absorbing column density, weight-averaged temperature, ionization age and abundances for O, Ne, Mg, Si, S and Fe, with emission used to determine the weight. The abundance maps and the finding that Fe abundance is not correlated with any other element suggest that Fe is located at a smaller radius than other elements,supporting the onion shell model with emission from more massive elements peaking more toward the center. A tight correlation between Si and S abundances support both Si and S coming from explosive O-burning and/or incomplete Si-burning. O and Ne abundances show no correlation with any other element. Considering that O, Ne and Mg are all synthesized in the same process(C/Ne-burning), we suggest that O/Ne/Mg might mix well with other elements during the explosion of the supernova and the expansion of the SNR. 相似文献
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《天文和天体物理学研究(英文版)》2014,(8)
We present large scale observations of C18O(1–0) towards four massive star forming regions: MON R2,S156,DR17/L906 and M17/M18. The transitions of H2CO(110–111),C18O(1–0) and the 6 cm continuum are compared in these four regions. Our analysis of the observations and the results of the Non–LTE model shows that the brightness temperature of the formaldehyde absorption line is strongest in a background continuum temperature range of about 3 – 8 K. The excitation of the H2 CO absorption line is affected by strong background continuum emission. From a comparison of H2 CO and C18 O maps,we found that the extent of H2 CO absorption is broader than that of C18 O emission in the four regions. Except for the DR17 region,the maximum in H2 CO absorption is located at the same position as the C18 O peak. A good correlation between intensities and widths of H2 CO absorption and C18 O emission lines indicates that the H2 CO absorption line can trace the dense,warm regions of a molecular cloud. We find that N(H2CO) is well correlated with N(C18O) in the four regions and that the average ratio of column densities is N(H2CO)/N(C18O) ～ 0.03. 相似文献
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《天文学进展》2017,(2)
中红外高电离发射线[OⅣ](25.9μm)的产生机制尚不明确。利用简单的光致电离模型,Hao等人(2009)初步分析发现,当星暴星系模型给出的[NeⅢ]/[NeⅡ]值与观测相当时,其给出的[OⅣ]/[SⅢ]值却比观测值低约4个量级。[OⅣ]/[SⅢ],[SⅣ]/[SⅢ],[NeⅢ]/[NeⅡ]等中红外发射谱线比值及其变化趋势,以及其与ITERA package中提供的各类更新的光致电离模型的比较,是进一步探索星暴星系中[OⅣ]发射来源的一种有效途径。观测数据与电离模型计算结果的比较表明,Hao等人(2009)中提出的中红外发射线诊断图[OⅣ]/[SⅢ]对[SⅣ]/[SⅢ]中的分支结构能分别较好地与AGN与星暴星系光致电离模型相吻合。这些星暴星系模型所产生的[OⅣ]发射的强度与电离光谱中大于4 Ryd段的相对光子流量呈紧密正相关,单独考虑Wolfe-Rayet星的辐射对电离光谱的贡献足以解释星暴星系中的[OⅣ]发射线;而对于[OⅣ]/[SⅢ]对[NeⅢ]/[NeⅡ]诊断图,模型仍很难解释观测结果,特别是星暴星系分支:当由模型计算出的[OⅣ]/[SⅢ]值与观测相当时,其给出的[NeⅢ]/[NeⅡ]值相比于观测仍明显偏高。如果考虑上述发射线均来自具有单一密度与电离参数的发射区,那么[NeⅢ]/[NeⅡ]值与电离光谱21.6～41.0 eV段的斜率密切相关。 相似文献
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大质量恒星形成区内分布着很多类型的脉泽,包括OH,H_2O,CH_3OH和SiO等。利用甚长基线干涉测量(very long baseline interferometry,VLBI)技术多历元观测脉泽,可以在10～100 AU的线尺度上反映年轻星附近的气体运动学特征。在各类脉泽中,H_2O脉泽是亮度最强的脉泽之一,因此是研究大质量恒星形成区外流的极佳示踪天体。H_2O脉泽在不同大质量恒星形成区内主要显示有准直喷流和宽张角外流等运动特征。选取了具有代表性的大质量恒星形成区,如Orion-KL,Cepheus A,W75N(B),G24.78+0.08 A1和AFGL 5142,介绍了H_2O脉泽在这些形成区所反映的气体运动学特征,及其与大质量恒星演化之间的关系。 相似文献