A search for absorption of Mg and Ca compounds in molecular clouds towards Galactic continuum sources

Absorption lines of MgH and CaH N  = 1 − 0 transitions were searched for in foreground molecular clouds towards the continuum sources associated with Sgr B2 (M) and W49A (N). None of these lines was detected with our sensitivity level of ∼20 mK. Millimetric absorption lines of MgO, MgOH, CaO and CaOH were also searched for towards Sgr B2 (M) without success. The fractional abundances relative to molecular hydrogen are ≲ 1.0 × 10⁻¹¹ for MgH, ≲ 7.9 × 10⁻¹³ for MgO, ≲ 1.6 × 10⁻¹⁰ for MgOH, ≲ 1.6 × 10⁻⁹ for CaH, ≲ 2.0 × 10⁻¹² for CaO, and ≲ 2.5 × 10⁻¹⁰ for CaOH, respectively. The low abundances measured in absorption indicate that a significant fraction of interstellar magnesium and calcium cannot be tied up in their monohydrides, monoxides and monohydroxides. The low abundance of MgH also implies that grain-surface chemistry involving magnesium is not efficient and that magnesium is depleted on to grains to a factor of ≳ 10^2.5 in well-shielded molecular clouds.     

Radio study of X-ray clusters of galaxies — I. A3528: a pre-merging cluster in the core of the Shapley Supercluster

As part of an extensive radio–IR–optical–X-ray study of ROSAT clusters of galaxies in the Hydra region we have observed the bimodal Abell cluster A3528, located in the core of the Shapley Supercluster ( z  ≃ 0.053), with the Molonglo Observatory Synthesis Telescope at 843 MHz and the Australia Telescope Compact Array at 1.4 and 2.4 GHz. This is part I in a series of papers which looks at the relationship between the radio and X-ray emission in samples of ROSAT selected clusters.   The radio source characteristics — tailed morphologies and steep spectra — are consistent with the effects of a dense intracluster medium and the pre-merging environment of A3528. In particular, we present evidence that the minor member of the radio-loud dumbbell galaxy located at the centre of the northern component of A3528 is on a plunging orbit. We speculate that this orbit may have been induced by the tidal interactions between the merging components of A3528. In addition, the radio source associated with the dominant member of the dumbbell galaxy exhibits many of the characteristics of compact steep spectrum sources. We argue that the radio emission from this source was triggered ∼ 10⁶ yr ago by tidal interactions between the two members of the dumbbell galaxy, strengthening the argument that compact steep spectrum (CSS) sources are young.   Re-analysis of archive pointed Position Sensitive Proportional Counter (PSPC) data using multiresolution filtering suggests the presence of an AGN and/or a cooling flow in the southern component of A3528.     

Regularities in the long-term optical light curve of the black hole candidate binary A0620 − 00 (V616 Mon)

We have monitored the R I magnitudes of the black hole candidate system A0620 − 00 (V616 Mon) in the years 1991–1995 at the Wise Observatory. Combining our data with some additional measurements, we analyse a sparsely covered 7-yr light curve of the star. We find that the average R -band magnitude varies on a time-scale of a few hundred days, with a peak-to-peak amplitude of 0.3 mag. The two maxima in the well-known double hump binary cycle, as well as one of the minima between them, vary by a few per cent relative to one another, in a seemingly random way. One maximum is, on average, higher by 0.05 mag than the other. The depth of the second minimum varies with significantly higher amplitude, in clear correlation with the long-term variability of the mean magnitude of the system. It is shallower than the other minimum at times of maximum light. It deepens when the system brightness declines, and it becomes the deeper of the two minima at times of minimum system light. According to the commonly acceptable phasing of the binary cycle, the systematically varying minimum corresponds to the inferior conjunction of the red dwarf. We cannot suggest any simple geometrical model for explaining the regularities that we find in the long-term photometric behaviour of the V616 Mon binary system.     

A substructure analysis of the A3558 cluster complex

The 'algorithm driven by the density estimate for the identification of clusters' ( DEDICA ) is applied to the A3558 cluster complex in order to find substructures. This complex, located at the centre of the Shapley Concentration supercluster, is a chain formed by the ACO clusters A3556, A3558 and A3562 and the two poor clusters SC 1327-312 and SC 1329-313. We find a large number of clumps, indicating that strong dynamical processes are active. In particular, it is necessary to use a fully three-dimensional sample (i.e. using the galaxy velocity as third coordinate) in order also to recover the clumps superimposed along the line of sight. Even though a large number of detected substructures was already found in a previous analysis, this method is more efficient and faster when compared with a wide battery of tests, and permits the direct estimate of the detection significance. Almost all subclusters previously detected by the wavelet analyses found in the literature are recognized by DEDICA . On the basis of the substructure analysis, we also briefly discuss the origin of the A3558 complex by comparing two hypotheses: (i) the structure is a cluster–cluster collision seen just after the first core–core encounter; or (ii) this complex is the result of a series of incoherent group–group and cluster–group mergings, focused in that region by the presence of the surrounding supercluster. We studied the fraction of blue galaxies in the detected substructures and found that the bluest groups reside between A3562 and A3558, i.e. in the expected position for the scenario of cluster–cluster collision.     

Smoke rings around supernova 1987a

Detailed observations of the [Oiii]5007 Å emission from the elliptical rings around SN 1987A suggest a model wherein the two faint, outer rings are due to emission from two circular toroids moving outwards (at 25 km s^–1) along a bipolar cone centred on the site of the supernova. The brighter, central ring is expanding radially outward at 8.3 km s^–1. The rings must have been created 2-3 × 10⁴ years before the supernova explosion and are thought to be a consequence of the interaction of stellar winds emanating from the progenitor system during the final stages of its evolution to a supernova.     

The small-scale outflow structure of embedded sources in taurus

High resolution interferometric COJ=1–0 observations of the outflows from two young embedded sources, TMC1 and TMC1A, show the high-velocity gas to have a conical structure, with a constant opening angle of 45° extending to within 1000 AU of the central stars. The correspondence of near-infrared reflection nebulosity atK band with blueshifted CO emission in both objects suggests the lobes are partially evacuated, as do position-velocity diagrams from single-dish COJ=2–1 data. We suggest that the outflows are driven by jets which impart momentum to the ambient medium through shocks, rather than through the entrainment of molecular material along the edges of the jet.The NRAO is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation     

赣南寨背A型花岗岩体的地球化学特征及其构造地质意义

赣南寨背岩体主要为黑云母钾长花岗岩,黑云母结晶晚于长石和石英,锆石群型地温测量标尺显示其结晶温度为８００℃～９００℃,表明寨背岩体形成于一种高温贫水的花岗质岩浆。岩石的化学成分特点为准铝质（Ａｌ２Ｏ３为１２．２１％～１２．６２％）,富硅（ＳｉＯ２为７５．６６％～７６．７４％）,偏碱（Ｎａ２Ｏ＋Ｋ２Ｏ为７．９３％～８．９０％）,ＦｅＯＴ／ＭｇＯ值高（５９～１４８）,ＣａＯ和ＭｇＯ含量低（分别为０．１０％～０．６５％和０．０１％～０．０２％）,富含ＲＥＥ（Ｅｕ除外,ΣＲＥＥ平均为５００μｇ／ｇ）,Ｙ、Ｇａ、Ｎｂ等高场强元素（ＨＦＳＥ）以及Ｆ,Ｓｒ和Ｂａ较低。这些特点与本区的Ｉ型和Ｓ型花岗岩有明显差别,是一种典型的Ａ２型花岗岩。寨背岩体Ｒｂ－Ｓｒ等时线年龄为１７６Ｍａ,与辉长岩、双峰式火山岩有密切的时空关系,表明赣南地区在燕山早期即进入拉张裂解阶段。     

对大洋多金属结核10A锰矿物相的研究

对大洋多金属结核中１０Ａ锰矿物的研究、认识长期以来众说纷纭。为探索我国研究区１０Ａ锰矿物的种类,本文从１００多个结核样品中,选出具代表性的以１０Ａ锰矿物为主的１３个样品,进行了热稳定性研究,且归纳总结为３种情况：有７Ａ衍射峰生成,且１０Ａ衍射峰向高角度移动,说明原样中有布赛尔矿Ⅰ型,钴土矿布赛尔矿混层矿物;无７Ａ衍射峰生成,但１０Ａ衍射峰也向高角度移动,说明原样中没有布赛尔矿Ⅰ型,而有钴土矿布赛尔矿混层矿物;无７Ａ衍射峰生成,且１０Ａ衍射峰基本消失,表明原样中有钴土矿。作者尚运用晶体结构理论对上述３种不同情况进行了解释;并得出,我国研究区结核１０Ａ锰矿物相中主要矿物种为布赛尔矿Ⅰ型、钴土矿布赛尔矿混层矿物及钴土矿,不存在或几乎不存在钡镁锰矿。     

多道轻便地震数据采集系统

详细介绍了４８道浅震仪数据采集系统的硬件组成及各部分的工作原理,并介绍了浅震仪数据采集系统的基本软件流程及编制软件原理。     

高分辨率地震勘探关键措施论述

以松辽盆地北部高分辨率勘探试验资料为基础,对其精细构造勘探中需注意的几个重要环节进行了系统的研究,并在某些环节上得出了与常规地震相悖的观点,如：应兼顾激发能量和频带宽度确定激发层位与药量;应根据勘探目的层的深浅,选择不同自振频率的检波器,检波器以多串少并方式连接,更有利于记录高频信号;在信号记录方面,提出应根据模/数转换器位数对频宽的影响程度选择低切;另外指出是否采用高分辨率地震勘探的依据是高频信息在浅层的衰减程度、目的层的物性条件及目的层的层数。针对施工中容易出现问题的环节,提出了应采取的措施,根据目前高分辨率地震勘探现状,提出未来需进一步攻关的方向。