Étude cinématique de la galaxie barrée NGC 5383

We present some observational results derived from plates taken with the nebular spectrograph at the 1.93-m telescope of the Observatoire de Haute Provence. The dispersion is 35 Å mm^?1 and the resolution is 85″ per mm. Radial velocities were measured at different points in the nucleus and in the bar. The nucleus is composed of two elements, of 5″ and 12″ diameter, inside a ring of radius 2 kpc. Radial velocities around the ring show a well-defined sinusoid with a maximum displaced about 15° from that predicted from the geometry of the outer parts of the galaxy. We can explain this displacement by a contraction velocity of 43 km s^?1. In the bar the kinematics is quite complex. The slit position (roughly aligned with the bar) was slightly different for each of the four plates taken. For those which bisect the nucleus the velocity field is symmetric, with a sharp discontinuity of 50 km s^?1 between the nucleus and the bar. The maximum velocity is not reached in our field of observation. Solid body rotation cannot be accepted. Spectra along the edge of the nucleus provides evidence for transverse motions in the bar of 100 km s^?1 at 4 kpc from the center. The rotation curve is drawn; in the hypothesis of a radial motion in the bar we have calculated the distribution of mass according to the method of Burbidge and Prendergast inside a 14 kpc radius; the mass is 10¹⁰ M _⊙. The iso-intensity tracings clearly show the presence of the two nuclear components, the absence of [Nii] emission on the north-west side of the bar and the absence of Hα in the south-west side. The ratio Hα/[Nii] between 2 and 5 at several spots indicates that Hii regions are highly excited in the nucleus and at the extreme end of the bar. The region of the bar where the ratio is less than 1 suggests high excitation by collision of energetic particle perhaps coming from the nucleus.     

A Kinematical Study of the NGC 7538 IRS 1 Region

We present high angular resolution images of both NH3(1,1)and (2,2) lines toward NGC 7538 IRS 1.The density and velocity-position plots have been used to study the interaction among the outflows,winds and their environment.For the first time we have found an expanding half-shell of molecular gas around the HⅡ region associated with IRS 1,which may be produced by the interaction of the bipolar outflows and the winds originating in IRS 1-3,and optical HⅡ region NGC 7538 with ambient molecular gas.     

Comptonization and Reprocessing Processes in Accretion Disks： Applications to the Seyfert 1 Galaxies NGC 5548 and NGC 4051

Simultaneous multi-wavelength observations have revealed complex variability in AGNs. To explain the variability we considered a theoretical model consisting of an inner hot comptonizing corona and an outer thin accretion disk, with interactions between the two components in the form of comptonization and reprocessing. We found that the variability of AGNs is strongly affected by the parameters of the model, namely, the truncated disk radius rmin, the corona radius rs, the temperature KTe and the optical depth τ0 of the corona. We applied this model to the two best observed Seyfert 1 galaxies, NGC 5548 and NGC 4051. Our model can reproduce satisfactory the observed SEDs. Our fits indicate that NGC 5548 may have experienced dramatic changes in physical parameters between 1989-1990 and 1998, and that NGC 4051 has a much larger truncated disk radius (700 Schwarzschild radii) than NGC 5548 (several tens of Schwarzschild radii). Since we adopted a more refined treatment of the comptonization process rather than simply assuming a cut-off power law, our results should be more reasonable than the previous ones.     

NGC 7538—IRS1致密HⅡ区研究

本文在分析研究NGC7538-IRS1致密HⅡ区H_2CO和OH脉泽辐射VLBI观测结果的基础上,指出该HⅡ区合理的模型是:HⅡ区表面为厚的尘埃层包围,尘埃层两极已被突破,并形成双极流;HⅡ区外面有一个环形转动气体-尘埃云,存在由环向HⅡ区表面的物质下落;包括环和HⅡ区在内的整个系统视向速度为-61km/s,该系统居于视向速度为-57km/s的更大分子云中。H_2CO和OH脉泽发生在HⅡ区两极附近离HⅡ区表面小于0.2R_(HⅡ)的区域内。利用上述模型,还讨论了H_2O脉泽及其他分子吸收线和发射线的发生区域。     

NGC 1333/IRA6-9 区域中的致密分子云核

利用紫金山天文台青海站的13．7m毫米波望远镜,对NGC1333／IRAS6－9附近的一个10．3'X10'和6．8'X8'的恒星形成区,进行了13CO（1－0）和C18O（1－0）的成图观测,发现了多个新的分子云核和沿SSV12－IRASS方向的13CO（1－O）双极外向流．本文给出了每个云核的观测特性和物理参数．分析了这一区域的云核分布和速度场结构．详细讨论了该区域的云核分布、双极外向流和群集的年轻天体、红外源以及HH天体的关系．     

CCD <Emphasis Type="Italic">UBV</Emphasis> photometric study of five open clusters—Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1

In this study, we present CCD UBV photometry of poorly studied open star clusters, Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1, located in the first and second Galactic quadrants. Observations were obtained with T100, the 1-m telescope of the TÜB?TAK National Observatory. Using photometric data, we determined several astrophysical parameters such as reddening, distance, metallicity and ages and from them, initial mass functions, integrated magnitudes and colours. We took into account the proper motions of the observed stars to calculate the membership probabilities. The colour excesses and metallicities were determined independently using two-colour diagrams. After obtaining the colour excesses of the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 as \(0.19\pm0.06\), \(0.15\pm0.05\), \(0.32\pm0.05\), \(0.12\pm 0.04\), and \(0.43\pm0.06\) mag, respectively, the metallicities are found to be \(0.00\pm0.09\), \(0.02\pm0.11\), \(0.03\pm0.07\), \(0.01\pm0.08\), and \(0.01\pm0.08\) dex, respectively. Furthermore, using these parameters, distance moduli and age of the clusters were also calculated from colour-magnitude diagrams simultaneously using PARSEC theoretical models. The distances to the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 are \(1050\pm90\), \(1610\pm190\), \(1210\pm150\), \(1060\pm90\), and \(1710\pm250\) pc, respectively, while corresponding ages are \(400\pm100\), \(750\pm150\), \(400\pm100\), \(600\pm100\), and \(175\pm50\) Myr, respectively. Our results are compatible with those found in previous studies. The mass function of each cluster is derived. The slopes of the mass functions of the open clusters range from 1.31 to 1.58, which are in agreement with Salpeter’s initial mass function. We also found integrated absolute magnitudes varying from ?4.08 to ?3.40 for the clusters.     

Les anneaux de saturne en 1969. Etude morphologique et photométrique. I. Obtention et dépouillement des photographies

Some excellent photographs of Saturn in yellow and violet light have been taken in 1969 with the 105cm reflecting telescope of the Pic du Midi Observatory. They revealed the existence, inside the C-ring, of an extremely faint, fourth Ring. The reduction of microphotometric tracings along the great-axis of the Rings, have given the photometric curves of the rings in the two colours above. These two curves are very similar. They do not agree with some of the details drawn before and show some new ones.     

Les anneaux de saturne en 1969. Etude morphologique et photométrique. II. Déconvolution des courbes photométriques

The objective of the present work is to improve the resolution of P. Guérin's photographs of the rings of Saturn by deconvoluting the raw photometric curves. First we search for the apparatus function from the exposure itself, then study theoretically the effective noise filter of several methods of deconvolution. The calculation by Fourier transform finally adopted uses the numerical multiplexing program of fast Fourier transforms. We gain at least a factor two in resolution. This permits us to deduce conspicuous intermediate steps in the Cassini division, and to ascertain that the center of this division is far from being dark and hence contains a certain quantity of matter.     

The Correlation between Optical Spectral Index and Continuum Luminosity Variation in the Seyfert 1 Galaxy NGC 5548

Using the archived optical spectra of NGC 5548 between 1989 and 2001, we derived the optical spectral index by fitting the spectra in wavelength windows unaffected by strong emission lines. We found that the index is anti-correlated with the continuum luminosity at 5100 A with a correlation coefficient of -0.8. Based on the standard thin accretion disk model, we investigated whether the correlation is related to the variations of the dimensionless accretion rate m (mass accretion rate in Eddington unit), or the inner radius of the accretion disk Rin, or both. The correlation can be modeled well using a co-variable mode of Rin/Rs = 12.5m-0.8 (Rs is Schwarzschild radius). As luminosity increases, m increases from 0.05 to 0.16 and at the same time Rin decreases from 133.9.RS to 55.5.RS, consistent with the prediction for a transition radius within which an ADAF structure exists. We concluded that the change of both inner accretion radius and the dimensionless accretion rate are key factors for the variation     

Radio-continuum study of the Nearby sculptor group galaxies. Part 1: NGC 300 at λ=20 cm

A series of new radio-continuum (λ=20 cm) mosaic images focused on the NGC?300 galactic system were produced using archived observational data from the VLA and/or ATCA. These new images are both very sensitive (rms?=60 μJy) and feature high angular resolution (<10?″). The most prominent new feature is the galaxy’s extended radio-continuum emission, which does not match its optical appearance. Using these newly created images a number of previously unidentified discrete sources have been discovered. Furthermore, we demonstrate that a joint deconvolution approach to imaging this complete data-set is inferior when compared to an immerge approach.     

New insights into a familiar friend: COJ=2–1 mapping of the bipolar outflow source NGC 1333 (HH 7–11)

We have observed the bipolar outflow source NGC 1333 (HH 7–11) in theJ=2–1 transition of¹²CO, and find evidence for a strong westerly termination of the red outflow lobe at a velocityV _lsr 27 km s^–1, together with maximal mean red-flow velocities v centred upon both the driving source SVS 13 and the westerly limit of the outflow zone. As a consequence, we propose a model for the source in which the red-shifted outflow is directly impinging upon a nearby molecular cloud, causing extensive surface erosion and/or diversion of the jet material.Paper presented at the 11th European regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

New Plateau de Bure observations of M 1–92; unveiling the core

M 1–92 is a very well studied bipolar pPN that can be considered an archetype of this type of sources; it shows a clear axial symmetry, along with the kinematics characteristic of this class of envelopes around post-AGB stars. We performed sub-arcsecond resolution observations of the J=2–1 rotational line of ¹³CO in M 1–92 with the new extended configurations of the IRAM Plateau de Bure interferometer, for studying the morphology and velocity field of the molecular gas better in the nebula, particularly in its central parts. We found that the equatorial structure dividing the two lobes is a thin flat disk, which expands radially with a velocity proportional to the distance to the central stellar system. The kinetic age of this equatorial flow is very similar to that measured in the two lobes, suggesting that the whole structure was formed as a result of a single event some 1200 yr ago, after which the nebula reached an expansion velocity field with axial symmetry. The small widths and velocity dispersion in the gas forming the lobe walls confirm that the acceleration responsible for the nebular shape could not last more than 100–120 yr. In view of the similarity to η Car, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a common-envelope system. The study of the possible importance of this mechanism in the context of global PNe and pPNe reshaping should be one on the fields in which future ALMA observations will make a crucial contribution. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).     

2003年9月26日1号小行星掩TYC 1896-01388-1u的预报

2003年9月26日凌晨北京时间4时54分到4时59分左右,1号小行星(谷神星)将掩食双子座一颗9.3等恒星TYC 1896-01388-1u,掩食带从中国北部地区穿过,希望有能力的爱好者能观测这一天象。不过被掩星比小行星本身还要暗,不知道会有什么结果。但至少我们可以看到两颗亮度相当的星逐渐接近,最后合为一体,也是很有趣的现象。从预报中可以看出,东经112     

1-2GHz太阳射电动态频谱仪

本文描述了北京天文台研制的１－２ＧＨｚ太阳射电动态频谱仪的性能、结构、初步观测结果及进一步改进计划．     

超新星遗迹MSH 15-56和CTA 1

对于超新星遗迹MSH 15-56和CTA 1,本文较详细地公布了由爱因斯坦卫星得到的X射线观测资料.根据这些资料,导出其物理特性,推导和预言其射电流量,并与前人的射电观测进行了比较.     

另类的星野赤道仪-宾得O-GPS1深入解读

上一篇文章,笔者详细介绍了宾得O-GPSl这个附件的设计原理和独特功用。接下来,我会给大家展示使用O-GPSl配合宾得单反相机拍摄星空的方法和一些优势,以及在对比真正的星野赤道仪时,各自的优缺点。     

3- to 14-μm Spectroscopy of Comet C/1999 T1 (McNaught-Hartley)

We report spectroscopy of Comet C/1991 T1 (McNaught-Hartley) at 3-13 μm on January 31.62 and February 1.7 2001 UT (delta=1.29 AU, r=1.40 AU) using the broadband array spectrograph system on the IRTF. The spectrum showed a silicate emission feature extending about 20% above the continuum. Two emission features at 10.3 and 11.2 μm appeared above the silicate band, the latter seemingly indicative of crystalline olivine. The 10.3-μm feature is only a 1-2 sigma detection but if real could indicate the presence of hydrated silicates. The color temperature at 8-13 μm was 260±10 K, approximately 6% above the blackbody radiative equilibrium temperature of 235 K. The magnitude at [N] was 3.13±0.02. On the second night, the comet had brightened slightly ([N]=2.98±0.02) and the two prominent emission features were absent, although the silicate emission feature maintained its trapezoidal shape with shoulders at 9.5 and 11.2 μm.     

行星状星云的CO(1-0)谱线观测

用紫金山天文台青海站的１３７ｍ射电望远镜,对１０个行星状星云给出了新的ＣＯ（１－０）谱线观测结果．其中４个行星状星云：ＮＧＣ６４４５,Ｍ１５９,Ｍ４９和Ｍ２５１,已有过ＣＯ（２１）的观测,本文第一次给出了它们的ＣＯ（１０）的测量结果;对２个别人曾经观测过但未测到ＣＯ的行星状星云：Ｓｈ２７１和Ｍ４１８,本文第一次证认了它们的ＣＯ发射;对４个别人从未进行过ＣＯ搜寻的行星状星云：ＶＶ１８,Ｍ２５２,Ｈｅ２４５９和Ｋ３３１,本文第一次进行了观测,并得到了它们的ＣＯ（１０）谱．由ＣＯ的发射谱征可见,ＶＶ１８可能是一个误分类的行星状星云     

初始谱指数为-1的非线性重谱(Bispectrum)

重谱即傅立叶空间的三点相关函数，是研究由引力不稳定性产生的大尺度结构的最低非高斯阶统计性质．在傅立叶空间中，发现二维和三维空间的统计性质是等价的，相对三维快速傅立叶，二维快速傅立叶变换可以节省很多计算机资源．结合二维和三维的快速傅立叶变换，利用高精度的初始谱指数为-1的N体数值模拟，测量了从弱线性区域到强非线性区域的重谱．在测量过程中，考虑并严格校正了作用于功率谱和重谱上的数值效应，如离散效应（particle discreteness）、软化因子（force softening）、模拟盒子的大小、混淆效应（alias effect）．发现约化重谱即使在强非线性区域仍然依赖于三角形的形状和尺度，并随着波数的增加而增加，这和前人的假设完全不同．在测量结果的基础上，拟合了重谱的一个适用于初始谱指数为-1的宇宙学模型的经验公式．