NGC7538的近红外偏振成像

介绍恒星形成区ＮＧＣ７５３８的Ｈ和Ｋｓ波段偏振成像的观测结果．近５′视场的偏振图像揭示了与亮红外源ＩＲＳ１１１成协的年轻星团和红外星云的复杂结构．ＩＲＳ１３星云的偏振图像表明星云的近红外辐射主要来自对深埋红外源ＩＲＳ１的反射;其形态可解释为颜色很红的高偏振的壳层包围着的低消光气泡．ＩＲＳ１周围的近红外的偏振强度在ＩＲＳ１双极分子外流方向上呈现出一较小的壳结构．ＩＲＳ４在近红外表现为双源,其中较红的源ＩＳＲ４ｂ周围观测到中心对称的偏振图像．ＩＲＳ５与亮星云成协,ＩＲＳ６则处于一组星的中心．在ＩＲＳ５和ＩＲＳ６周围的星云中没有观测到偏振．ＩＫＳ９照亮着两块星云,ＩＲＮ１和ＩＲＮ２．ＩＲＮ１星云有很好的锥形并包含一高偏振的喷流成分．云中较高偏振的部分对应较蓝的颜色,显示着其较大的视向张角的外流腔结构．与复杂的ＩＲＳ９区分子外流相比较,ＩＲＮ１星云与在ＮＥＳＷ方向的外流相符合．首次证认了ＩＲＳ１１近红外点源,并观测到其周围有一组星和很暗的星云物质     

S255IR复合体的近红外偏振测量

介绍恒星形成区Ｓ２５５ ＩＲ 复合体的Ｈ 和Ｋｓ 波段成像偏振和对其中红外源ＩＲＳ１在１ ．２ － ４ ．２ μｍ 上的分光偏振测量．偏振图像揭示了Ｓ２５５ － ２ 核区的两类近红外辐射．以ＩＲＳ１ 双源为中心的一条亮云脊表现出高偏振,而周围延展云却基本上无偏振．偏振图样进一步显示出由ＩＲＳ１ａ 和１ｂ 分别照射的两块反射云．它们都呈双极结构,并且其轴向近于相互垂直．由ＩＲＳ１ｂ 照射的双极云位于方位角ＰＡ～６５°,与Ｈ２ 发射的双极喷流现象很好地符合．两个照射源都是深埋天体．ＩＲＳ１ｂ 和高密度拱星盘成协,其盘平面与双极云垂直．ＩＲＳ１ａ可能也与一未能分辨的盘结构成协,东西方向的盘同样与其成协反射云垂直．从ＩＲＳ１ 的分光偏振测量可辨认出３ μｍ 水冰吸收波段上的偏振超．在此吸收波段上还观测到了反转型的偏振角旋转     

IRAS05391—0217和IRAS06572—0742源的热动性质

利用紫金山天文台青海观测站１３．７米射电望远镜对源ＩＲＡＳ０５３９１０２１７和ＩＲＡＳ０６５７２０７４２进行了１２ＣＯＪ＝１－０观测,获得了气体的相应参数;用ＩＲＡＳ及其他红外观测资料,获得了尘埃热结构;探讨了云中气体的热平衡．对于ＩＲＡＳ０５３９１０２１７中由远红外得出的Ｔｄ＜Ｔｋ的情形,考虑了几种可能的加热机制．光电加热对该云可能是比较重要的;激波可能是另一种加热途径．     

SiO脉泽星的近红外测光与分析

本文给出３５个不同类型含ＳｉＯ（ｖ＝１,Ｊ＝１－０）脉泽发射的ＡＧＢ星的近红外观测结果（其中包括６个Ⅰ型ＯＨ星,１３个Ⅱ型ＯＨ星,９个仅有ＳｉＯ脉泽的星以及７个无ＯＨ脉泽但有ＳｉＯ和Ｈ２Ｏ脉泽的星）．得出了它们的ＪＨＫ星等和流量．同时经认证找出了它们对应的ＩＲＡＳ观测数据．通过对它们的近红外、中远红外以及ＯＨ射电资料的同时分析,得出了不同类型ＳｉＯ脉泽星的色指数、谱斜率以及在近红外波段上拟合的等效黑体温度Ｔｅｑ．由红外及ＯＨ射电资料导出了其中心星的质量损失率Ｍ,并在此基础上结合已知的ＳｉＯ脉泽源资料,找出了不同类型ＳｉＯ脉泽星各量之间的关系．计算结果表明,ＳｉＯ脉泽具有普遍性,在各类脉泽星中都可出现．ＳｉＯ脉泽的光度与质量损失率弱相关,并且从（Ｍｉｒａ）ＳｉＯ到（ＯＨ／ＩＲ）ＳｉＯ逐渐增加．ＳｉＯ脉泽的流量与近红外“色”以及等效黑体温度Ｔｅｑ的关系较为密切．ＳｉＯ脉泽积分流量的上限与ＩＲＡＳ在１２μｍ和２５μｍ上流量分别都相关．本文对ＳｉＯ脉泽在ＡＧＢ演化中的地位和特殊性进行了简单讨论．     

OMC--3的13CO(1--0)和C18O(1--0)分子辐射

利用紫金山天文台青海站的 １３．７ ｍ毫米波望远镜,对 Ｏｒｉｏｎ Ａ分子云中的 ＯＭＣ－３区域,进行了较高分辨率的１３ＣＯ（Ｊ＝１－０）和Ｃ１８Ｏ（Ｊ＝１－０）分子辐射的成图观测．给出了该分子云中１３ＣＯ和 Ｃ１８Ｏ云核分布的整体结构和平均物理参数．观测发现,该分子云的１３ＣＯ和 Ｃ１８Ｏ的云核中心分别与最年轻的天体－Ｃｌａｓｓ ０类源 ＭＭＳＩ, ＭＭＳ４,ＭＭＳ６和ＭＭＳ７,ＭＭＳ８;ＭＭＳ９成协．此外,通过分析ＯＭＣ－３整个区域的速度场结构,发现沿 Ｃ１８Ｏ和１３ＣＯ云核方向从南到北有一个～ １．７ｋｍ／ｓ的速度场梯度,而分子云的红、蓝移团块则分别趋于云的北部和南部．并对ＯＭＣ－３区的恒星形成特征进行了讨论．     

强IRAS远红外源的CO谱线观测

用紫金山天文台青海站的１３７ｍ射电望远镜对２７个强ＩＲＡＳ远红外源（流量Ｆ１００μｍ５００Ｊｙ）进行了ＣＯ（１－０）的谱线观测．观测表明,２７个强ＩＲＡＳ源全部与分子云成协,并与大质量星的形成或早期演化有关．其中１３个源是第一次给出ＣＯ（１－０）的谱线测量结果．本文对这一类源ＣＯ发射的性质进行了简单的讨论．     

OMC—3的^13CO（1—0）和C^18O（1—0）分子辐射

利用紫金山天台青海站的１３．７ｍ毫米波望远镜,对ＯｒｉｏｎＡ分子云中的ＯＭＣ－３区域,进行了较高分辨率的＾１３ＣＯ（Ｊ＝１－０）和Ｃ＾１８Ｏ（Ｊ＝１－０）分子辐射的图观测,给出了该分子云中＾１３ＣＯ和Ｃ＾１８Ｏ的云核中心分别与最年龄的天体－Ｃｌａｓｓ０类源ＭＭＳＩ,ＭＭＳ４,ＭＭＳ６和ＭＭＳ７,ＭＭＳ８,ＭＭＳ９成协,此外,通过分析ＯＭＣ－３整个区域的速度场结构,发现沿Ｃ＾１８Ｏ和＾１３ＣＯ云核     

近红外变源IRAS 04000 5052为一小尺度致密恒星形成区

利用瑞士Ｇｏｒｎｅｒｇｒａｔ天文台的意大利１．５米ＴＩＲＧＯ红外望远镜对近红外交源ＩＲＡＳ０４０００＋５０５２进行了近红外成像观测,得到了ＪＨＫ宽带及Ｈ２Ｓ（１）１～０和Ｂｒ窄带高分辨率图像,并进行了红外测光及位置测量工作．结果发现此ＩＲＡＳ源不是以往认为的单一年轻天体,而是一个包含有许多个年轻天体的小尺度致密恒星形成区,在这样小尺度且致密区域内,恒星形成也不是在同一时期完成的．     

AGB星的ISO观测

概述了ＩＲＡＳ升空以来在ＡＧＢ星研究方面的进展和发现的问题,比较详细地报告了６０ｃｍ空间红外望远镜ＩＳＯ携带的探测器及其性能,以及它的成像和光谱观测对研究ＡＧＢ星的演化的影响,尤其是对ＡＧＢ星星周包层的化学环境的研究的重要作用。     

近红外变源IRAS 04000＋5052为一小尺度致密恒星形成区

利用瑞士Ｇｏｒｎｅｒｇｒａｔ天文台的意大利１．５米ＴＩＲＧＯ红外望远镜对近红外变源ＩＲＡＳ０４０００＋５０５２进行了近红外成像观测,得到了ＪＨＫ宽带及Ｈ２Ｓ（１）１￣０和Ｂｒγ窄带高分辨率图像,并进行了红外测光及位置测量工作。结果发现此ＩＲＡＳ源不是以往认为的单一年轻天体,而是一个包含有许多个年轻天体的小尺度致密恒星形成区,在这样小尺度且致密区域内,恒星形成也不是在同一时期完成的。     

A thermodynamic model of high temperature lava vaporization on Io

We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the ONaKFeSiMgCaAlTi system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B1 Ca, Al-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for Io's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match Io's atmospheric Na/K ratio of 10±3 reported by Brown (2001, Icarus 151, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl₂, MgS, MgCl, FeCl₂, FeS, FeCl, and SiS.     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews 011 all liranchcs of astronoiriy and astrophysics.Reviews arc by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages).Authors who submit a paper are expected to be able to certify that the paper is original work,     

Research in Astronomy and Astrophysics CONTENTS

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Alkali and halogen chemistry in volcanic gases on Io

We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10⁻⁶ to 10⁺¹ bars) ranges, which overlap the nominal conditions at Pele (T=1760 K, P=0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. The elemental abundances for O, S, Na, K, and Cl are based upon observations. CI chondritic elemental abundances relative to sulfur are used for the other alkalis and halogens (as yet unobserved on Io). We predict the major alkali species in Pele-like volcanic gases and the percentage distribution of each alkali are LiCl (73%), LiF (27%); NaCl (81%), Na (16%), NaF (3%); KCl (91%), K (5%), KF (4%); RbCl (93%), Rb (4%), RbF (3%); CsCl (92%), CsF (6%), Cs (2%). Likewise the major halogen species and the percentage distribution of each halogen are NaF (88%), KF (10%), LiF (2%); NaCl (89%), KCl (11%); NaBr (89%), KBr (10%), Br (1%); NaI (61%), I (30%), KI (9%). We predict the major halogen condensates and their condensation temperatures at P=0.01 bar are NaF (1115 K), LiF (970 K); NaCl (1050 K), KCl (950 K); KBr (750 K), RbBr (730 K), CsBr (645 K); and solid I₂ (200 K). We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. Their estimated photochemical lifetimes range from a few minutes for alkali iodides to a few hours for alkali fluorides. Condensation is apparently the only loss process for elemental iodine. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observations of brown dwarfs we also recommend a search of Io's extended atmosphere and the Io plasma torus for neutral and ionized Li, Cs, Rb, and F.     

Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope.     

Born–Infeld type phantom model in the ω–ω′ plane

In this paper, we investigate the dynamics of Born–Infeld (B–I) phantom model in the ω–ω′ plane, which is defined by the equation of state parameter for the dark energy and its derivative with respect to N (the logarithm of the scale factor a). We find the scalar field equation of motion in ω–ω′ plane, and show mathematically the property of attractor solutions which correspond to ω _φ ∼−1, Ω _φ =1, which avoid the “Big rip” problem and meets the current observations well.      

A Comparison of Several Image Locating Algorithms in Astronomical Instruments

In astronomical observations at optical wavelengths, a fast image tracking system can be adopted to reduce the effects of the atmospheric seeing and telescopic tracking error, and therefore improve the observing efficiency. Aiming at the need of astronomical observations, totally 5 kinds of algorithms in two categories were selected to make a comparative study on their accuracies and stabilities under different noise conditions by both numerical experiment and laboratory test. The results indicate that the normalized cross-correlation method and barycenter method have not only a higher accuracy but also a better reliability against interferences, they will be applied to the high-resolution spectrograph of the Xinglong 2.16 m telescope and the scienti?c instruments of the SONG (Stellar Observations Network Group) project, respectively.