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排序方式: 共有170条查询结果,搜索用时 15 毫秒
71.
钱善皆 《中国天文和天体物理学报》2000,20(4)
以类星体0917+624中1989年5月观测到的IDV事件为实例,尝试提出一个4成分模型(1个稳定成分和 3个闪烁成分)以充分解释在 6 cm波长上观测到的偏振变化,包括流量和偏振流量的相关性和反相关性以及它们之间的快速转化.对于 20 cm波长上观测到的偏振变化,3成分模型(1个稳定成分和3个闪烁成分)已足以解释全部现象.文中提出的闪烁模型在解释IDV事件的偏振变化方面改进了以前的模型拟合. 相似文献
72.
通过对 W3(OH)区域 22 GHz H_(2)O脉泽源的短时间跟踪观测,探测到速度为-52.8 km/s子谱的流量密度呈线性下降趋势,变化时标约为 19天.同时也观测到了整个脉 泽源的谱线宽度与该子谱的强度之间的相关变化.这些现象可能是由脉泽云之间的相 互碰撞导致脉泽抽运率的变化所引起的。 相似文献
73.
74.
T. J. Cornwell D. J. Saikia P. Shastri L. Feretti G. Giovannini P. Parma C. J. Salter 《Journal of Astrophysics and Astronomy》1986,7(2):119-129
We present VLA A-array observations at λ20, 6 and 2 cm and B-array observations at λ20 and 6 cm of the quasar B2 1320 + 299,
which has a very unusual radio structure. In addition to a component, A, coincident with the quasar, there are two lobes of
radio emission, B and C, on the same side of A. These are located at distances of -25 and 50 arcsec respectively from A. The
present observations show that A has a flat-spectrum component coincident with the quasar and a weak outer component at a
distance of-4 arcsec along PA - 100°. The morphology of B resembles a head-tail type of structure with its tail towards the
north-east. The magnetic field lines in component B appear to follow the bend in the tail. Component C exhibits some extension
towards the north-west. We discuss the possible nature of B2 1320 + 299 and suggest that while A appears to be an independent
source, the relation between B and C, if they are associated at all, is unclear. Deep optical observations are essential to
help clarify the situation. 相似文献
75.
在相对论喷束模型中,假设源的核在观测者静止坐标系中不动的前提下,推出了现在已得到广泛承认和采用的计算相对论等离子团横向视速度的公式.随着观测精度的提高,对核固定不动的假设提出了怀疑,认为有必要重新估价表现横向速度公式的正确性,并在更普遍的框架下,找出该公式的修正形式.本文试图对几种根据目前对射电源一般结构认识提出的模型,初步探讨这种修正的可行性. 相似文献
76.
P. R. Wood 《Astrophysics and Space Science》1994,217(1-2):121-130
The stars that will be detectable in the Magellanic Clouds by the DENIS and 2MASS near infrared surveys are enumerated. All thermally-pulsing AGB stars will be observable in I, J, H and K, along with the top two magnitudes of both the early-AGB and the first giant branch. All carbon stars will be visible, and normal (N type) C stars will be easily distinguished by their large J-K colours. However, it will not be possible to separate faint, warm C stars from K and M stars using the photometry alone. Photometry of AGB stars in clusters will allow an accurate evaluation of the AGB tip luminosities as a function of initial mass. Random phase K magnitudes of LPVs and Cepheids should provide a better measure of the LMC tilt and distortions in the SMC. The K survey should turn up 100 to 150 objects undergoing superwind mass loss, these objects being OH/IR stars and the dust-enshrouded C star equivalents of OH/IR stars. It is shown that crowding should not be a problem even in the LMC bar. 相似文献
77.
78.
俞志尧 《中国天文和天体物理学报》1994,(3)
我们用ⅢZw35的流量密度函数,来拟合观测得到的OHmegamaser辐射谱。OHmegamaser斑点处在窄线区薄盘上,作旋转运动和径向膨胀运动。窄线区薄盘是侧向的。从理论上我们得到OHmegamaser辐射流量密度.发现与其辐射谱中主峰和伴峰相对应的OHmegamaser斑点处在窄线区薄盘的不同位置。 相似文献
79.
自从首次发现河外星系OH超脉泽以来,30多年(特别是近10年)中对河外星系OH超脉泽的观测和研究取得了极大的进展。到目前为止已发现106个河外星系OH超脉泽,其中包括59个较高红移的源。对河外星系OH超脉泽的观测和研究,是探测和研究其所成协的活动星系核、星暴星系的中央源和拱核盘的有效工具。主要评述对河外星系OH超脉泽的搜索、观测和理论研究现状。 相似文献
80.
L. Harvey-Smith † R. J. Cohen 《Monthly notices of the Royal Astronomical Society》2006,371(4):1550-1558
Images of the 6.7-GHz methanol maser emission from W3(OH) made at 50- and 100-mas angular resolution with the Multi-Element Radio-Linked Interferometer Network (MERLIN) are presented. The masers lie across the western face of the ultracompact H ii region in extended filaments which may trace large-scale shocks. There is a complex interrelation between the 6.7-GHz methanol masers and hydroxyl (OH) masers at 1.7 and 4.7 GHz. Together the two species trace an extended filamentary structure that stretches at least 3100 au across the face of the ultracompact H ii region. The dominant 6.7-GHz methanol emission coincides with the radio continuum peak and is populated by masers with broad spectral lines. The 6.7-GHz methanol emission is elongated at position angle 50° with a strong velocity gradient, and bears many similarities to the methanol maser disc structure reported in NGC 7538. It is surrounded by arcs of ground state OH masers at 1.7 GHz and highly excited OH masers at 13.44 GHz, some of which have the brightest methanol masers at their focus. We suggest that this region hosts the excitation centre for the ultracompact H ii region. 相似文献