杏梅坞秋韵     

刘金保 《浙江国土资源》2011,(3):59

春之美无人不晓,可与之相比,我则更喜欢枫叶红遍,秋高气爽的凝重。晚秋,得以常安之行,我们走进了"最美秋色"的杏梅坞。簿雾弥漫,太阳隐蔽在深深的云层后面,海拔400余米的杏梅坞呈现出一派别处初冬的超然。  相似文献   

Expected Number Counts of Radio Galaxy Clusters     

Wei Zhou National Astronomical Observatories  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2002,2(2):106-111

1 INTRODUCTION Over the past years, diffuse radio halos have been detected in a few tens of nearby, richclusters. They often extend to a distance of 1 Mpc from the cluster centers, and have regularshape, low surface brightness and steep radio spectrum. Some clusters also contain peculiarradio structures called radio relics. Both radio halos and relics are believed to arise from themerging of sub-cluster structures (Buote 2001). The first radio halo, Coma C, was detected about 30 years a…  相似文献   

河外TeV能段γ射线背景下限的估算          下载免费PDF全文

屈艳坤  曾厚敦 《天文学报》2021,62(6):67

Fermi卫星对GeV能段的河外伽马射线背景(Extragalactic Gamma-ray Background, EGB)进行了较为精确的测量, 极大提高了对高能伽马射线背景的认识, 但是在TeV能段, 使用空间探测器进行观测非常困难, 只能依赖地面伽马射线探测器, 如成像大气切伦科夫望远镜. 目前, 对于TeV能段的河外伽马射线背景的认识还不完善. 使用有低活跃状态能谱的61个TeV源(包含2个星暴星系、6个射电星系以及53个耀变体)的累计流量给出河外TeV伽马射线背景的下限. 结果显示, 低能段(0.5--4.5TeV)流量由两个临近的耀变体Mrk 421和Mrk 501主导, 贡献了大约58%的累计背景流量; 而大于4.5TeV的能段, 由3个已观测到10TeV以上能段流量的极端耀变体H 1426+428、1ES 1959+650以及1ES 0229+200主导. 最后分别探究了星暴星系、射电星系以及耀变体对河外TeV伽马射线背景的贡献, 不同耀变体子类对河外TeV伽马射线背景的贡献以及不同红移区间TeV源对河外伽马射线背景的贡献.  相似文献   

Searching for Variable Stars in the Field of NGC 7789     

Xiao-Bin  Zhang  Li-Cai  Deng 《中国天文和天体物理学报》2003,3(2):151-165

We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified). In addition, we recovered 11 old variables previously discovered by other authors. Preliminary parameters are given for some of these variables.  相似文献