云南天文台光电等高星表

本文给出了云南天文台Ⅱ型光电高等仪1976年12月至1981年12月观测期间所得到的182颗两次过等高圈恒星的星位置改正值和部分一次过等高圈恒星的星位置改正值。并用这些改正值计算了FK_4星表的区域性系统差。     

第十一届国际天文奥赛实测题高年组

1.恒星监测。在孟买对一颗亮星整夜进行监测。使用14″望远镜,在三个波段(B,V,R)。假设观测波长对于观测恒星可以近似为有效波长450nm,550nm 和700nm。随着夜晚时间的不同,恒星在不同的天顶距被观测,因此星光穿过不同厚度的地球大气。由此,由地球大气产生的消光(ex-tinction)也在发生变化。消光值在恒星最     

星系中恒星形成率指针的比较研究

利用赫歇尔空间望远镜的H-ATLAS(Herschel Astrophysical Terahertz Large Area Survey)SDP(Science Demonstration Phase)天区从紫外到亚毫米波段数据,结合星族合成方法和尘埃模型,计算了星系的红外总光度.在此基础上,分别针对强恒星形成星系和弱恒星形成星系,研究了利用紫外光度、红外光度和Hα谱线计算得到的恒星形成率(Star Formation Rate,SFR)的差异以及导致差异的内在物理起因.发现对于恒星形成活动强的星系,这3种恒星形成率指针给出的结果基本一致,弥散较小、只是在高恒星形成率端,利用紫外光度算得的恒星形成率比利用Hα谱线流量算得的恒星形成率略微偏小;而在低恒星形成率端,紫外光度指针偏大于Hα谱线指针;红外光度指针与Hα谱线指针在两端无明显偏差.对弱恒星形成星系,紫外光度、Hα谱线和红外光度3种恒星形成率指针存在明显的差异,且弥散较大.利用紫外光度和Hα谱线计算得到的恒星形成率的弥散和系统偏差随着星系年龄、质量的增加而增大.系统偏差增大的主要原因是利用紫外连续谱斜率β定标恒星形成活动较弱星系的消光时,高估了这些星系的紫外消光,使得消光改正后的紫外光度偏大.另外,MPA/JHU(Max Planck Institute for Astrophysics/Johns Hopkins University)数据库中弱恒星形成星系的恒星形成率SFR(Hα)比真实值偏低.     

CCD光度定标对星像精确测量的影响

近年来,在用CCD器件进行恒星星像的位置和光度的精确测量中,有些研究者考虑了器件的光度定标(或称平场)的改正,有些人却不加说明地忽略之。在今后对恒星或行星星像的精确测量中是否需要考虑这种定标影响呢?为回答这一问题,我们利用在云南天文台1m望远镜上配备的CCD拍摄的实际图像进行了分析处理。当假定CCD每一像素光度的响应与输入光度具有线性关系的模型时,试验表明:对于暗星(约16mag),由光度定标引起的光度影响和位置影响分别约为0.2mag和0.02pixel,而对于亮星(约10mag),相应的改正在光度和位置方面分别约为0.02mag和0.002pixel。明显地,我们应该重视暗星星像的光度改正效应,而星像位置方面的效应则可以忽略不计。     

陕台光电等高仪(Ⅰ型)初始星表(摘要)

1978年初至1981年初,我们用陕台光电等高仪(Ⅰ型)进行了专门的星表观测。获得的星表包括777颗两次过等高圈的恒星的赤径改正△α和赤纬改正△δ。其中有FK4星357颗,FK4supp星189颗,GC星231颗。对于|cosq|≤0.3的星没有计算△δ。所有FK4星△α、△δ的平均精度分别为±0.0036和±0″.063。另外,还给出了43颗一次过等高圈的恒星的赤经改正△α和2颗星的赤纬改正△δ。为有效地扩充待测星数,除在时间、纬度观测纲要即基本组(2小时一组)内插入适当数目的待测星外,我们增加了星表组(1小时一组)。观测方案是:星表组——基本组——星表组——星表组——基本组——星表组或者星表组——基本组——基本组——星表组。星表的系统完全由基本组的FK4星决定。将各基本组化到平均系统以后,所有的星表组及基本组内的插入星直接相对于这个平均系统求其残差平均值。     

1984—1992年中国天文年历恒星视位置赤经改正表

1984—1992年中国天文年历中恒星视位置表没有包括系统差和个别改正。本文提供恒星视位置赤经改正表和赤纬改正表,用以改正到FK5系统。     

1984—1992年中国天文年历恒星视位置赤纬改正表

1984-1992年中国天文年历中恒星视位置表没有包括系统差和个别改正。本文提供恒星视位置赤经改正表和赤纬改正表,用以改正到FK5系统。     

用CCD作恒星测光的精度和误差分析——CCD天文测量方法(Ⅰ)

本文介绍了CCD图象预处理的数学模型和测量恒星星等的计算方法。并用数学模型讨论了天空背景,平扬改正,噪声和坏象元对星等测量的影响。分析结果表明,云台的Ⅰ号CCD系统的星等测量误差一般小于0.03个星等。     

章动常数改正的测定

本文提出在由以河外星系为定标的恒星自行与恒星星表自行相比较求解岁差常数改正的方法中,同时考虑章动常数误差的影响,进而在求解岁差常数采用值的改正值的同时确定章动常数采用值的改正值。     

我国的综合授时赤经星表

我国综合授时赤经星表(简称CTC),是利用我国五个天文台站(上海天文台,紫金山天文台,北京天文台,陕西天文台以及上海天文台的海南岛临时观测站)的五个光电中星仪和一个目视中星仪测时资料综合而成的.该星表共包括星等范围为0.~m1-6.~m6,赤纬区间为-30°- 66°的1156颗恒星。该星表以FK_4星为基础进行了恒星赤经的个别改正和系统修平,未进行春分点改正和没有建立自己自行系统,因此是一个相对星表.该星表采用了3-5年的观测数据,总观测星次达76847次,从而达到了比较高的精度,尤其是在赤纬带-5°- 56°范围内的1043颗星,其定位精度一般均优于±4ms.在本文中给出了CTC星表的编算方法及其精度.由于CTC星表已专刊发表,本文仅发表CTC星表的三个台站以上观测过恒星的赤经位置(1975.0历元),观测历元,观测次数,赤经位置的总精度σ及内部精度m,以供今后星表工作参考.     

Cloudy circumstellar dust shells around young variable stars

A number of variable stars of the Orion population has been identified with IRAS point sources by us. This finding supports the conclusion that the prominent Algol-like minima in the lightcurves of these stars originate from obscurations by dust clouds in a circumstellar shell. The discussion of the existingUBVR data leads to the remarkable conclusion that the extinction properties of the grain populations contained in individual dust clouds moving in one and the same circumstellar shell are quite different.From the multicolour photometric data of the different Algol-like minima we derived individual values of the reddening parameterR = A _v /E(B - V). It covers a remarkable wide range of values from that one typical of the interstellar extinction law up to 7. In the case of SV Cep one of the grain populations produces a virtually neutral extinction. The large values ofR speak in favour of larger than normal (interstellar) dust grains, which may have grown by coagulation processes. The cloudy circumstellar dust shell provides a natural explanation for the observed infrared excess. The properties derived from the optical light variations are fully compatible with the properties deduced from the infrared radiation. The irregularity of the light variations indicates that many clouds are involved and may sometimes superimpose themselves.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.     

Circumstellar dust and circumstellar extinction curves

We have calculated the circumstellar extinction curves produced by dust grains which absorb and scatter the stellar radiation in the shells of pre-main-sequence stars. A Monte Carlo method was used to model the radiative transfer in non-spherical shells. The dependence on the particle size distribution and the dust shell parameters has been examined.The application of the theoretical results to explain the extinction and polarization of the Herbig Be star HD 45677 shows that the dust shell is not disk-like and that very small grains are absent in it.     

Near infrared observations and analyses of molecular outflows

We present results of near infrared observation of 21 molecular outflow sources and two non-outflow sources with compact cores. Combined with IRAS and other surface station observations we analyse their spectra and find that the outflow sources have, on average, steeper spectral gradients than the non-outflow sources in the range 2.28–25 μ. Most of the bipolar outflow sources have gradients greater than 2.0. Using a revised blackbody photosphere model we calculate the contributions to the JHK fluxes by the central young star and the circumstellar envelope. For the sources with known bolometric luminosity we derive the photospheric temperature of the central star and the circumstellar extinction. Results show that most of the young stars associated with molecular outflows are probably T Tauri stars (5000–7000 K) or emission line stars (9000–26000 K). The circumstellar extinction in JHK is around 10 to 20 magnitudes. These facts show that molecular outflow sources are young objects still embedded deep inside or around the interior of compact cores. Fitting the 3.5– 25 μ and 60–100 μ spectra with a λ^-1 dust emission model to five source gives a negative power law for the temperature profile of the circumstellar shell with exponents between 0.39 and 0.48, close to the theoretical results for molecular clouds associated with HI I regions.     

晚型星红外谱拟合的线性化方法

本文针对晚型星红外辐射的一些模型，讨论相应的拟合方法。对有拱星壳层的晚型星的双黑体模型，给出了具体的拟合方法──线性化方法。最后我们就拟合结果及拟合程序编制方面讨论了线性化方法的优缺点。     

Dust shells of distant young stars

TheIRAS colours of some B stars with anomalous UV extinction confirm that they have circumstellar dust.     

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。     

Observations and Modeling of B[e] Stars

We give a short definition of B[e] star and we show spectrocopicvariabilities obtained for the peculiar star HD 45677 especialy for the strong He I line at 5876 Å. We present also some photometric observations for this type of stars that show a important excess in thenear and mid infrared due to the presence of circumstellar dust. The modelingof these stars shows that a simple model with a spherical dust shell fits well the observations. High spatial resolution gives an additional constraint on the modeling.     

Surface distribution of M stars with different IRAS colour

The surface distribution of M stars is studied by differentiating them according to whether they show a circumstellar dust shell (CS) or not. Analysis shows that galactic latitudinal and longitudinal distributions are not determined by spectral subclasses alone. The study also indicates that M-type stars with CS have higher luminosities in the K band than those without CS. The M stars used in the study are obtained from theTwo-Micron Sky-Survey Catalogue (IRC) which is a most unbiased sample with respect to the interstellar extinction. The CS feature is identified by the ratio of flux densities at 12 and 25 m in the IRAS point source catalog.     

The ney-allen nebula: an unambiguous example of circumstellar dust emission

Diffraction-limited array images of the Trapezium/Ney Allen infrared nebula have been obtained at six wavelengths between 7.8 and 12.4 microns, including the 9.7 micron silicate feature. Extended emission from warm dust shows significant differences in structure around each of the four Trapezium stars. The most dramatic infrared source is associated with ¹ Orionis D, where the bright mid-infrared emission is found to be a distinct crescent-shaped ridge or shell, concentric with the O star. This unambiguous relationship between a known type stellar luminosity source and a distinct circumstellar dust cloud of known distance and dimensions provides a unique opportunity to test the predictions of dust grain emission models for circumstellar infrared sources.     

Spectroscopic Study of Carbon Stars with the ISO-SWS

We have observed ten carbon stars with different mass-loss rates using the Short Wavelength Spectrometer (SWS) on board ISO. We found that not only the spectral energy distribution and the dust features, but that also that the strength and/or shape of molecular absorption features in the infrared spectrum varies with the near-infrared color temperature, i.e. with the thickness of the circumstellar envelope. This revised version was published online in August 2006 with corrections to the Cover Date.