Cosmic Ray Acceleration Inside Molecular Clouds     

V. A. Dogiel  A. V. Gurevich  Ya. N. Istomin  K. P. Zybin 《Astrophysics and Space Science》2005,297(1-4):201-211

Acceleration of charged particles by neutral gas turbulence in giant molecular clouds is considered. The gamma-ray emission from these clouds is estimated. It is shown that molecular clouds can be the counterparts of some of unidentified sources.  相似文献   

Outburst of the X-ray transient SAX J1818.6-1703 detected by the INTEGRAL observatory in September 2003     

S. A. Grebenev  R. A. Sunyaev 《Astronomy Letters》2005,31(10):672-680

During the observation of the Galactic-center field by the INTEGRAL observatory on September 9, 2003, the IBIS/ISGRI gamma-ray telescope detected a short (several-hours-long) intense (～380 mCrab at the peak) outburst of hard radiation from the X-ray transient SAX J1818.6-1703. Previously, this source was observed only once in 1998 during a similar short outburst. We present the results of our localization, spectral and timing analyses of the object and briefly discuss the possible causes of the outburst. The release time of the bulk of the energy in such an outburst is appreciably shorter than the accretion (viscous) time that characterizes the flow of matter through a standard accretion disk.  相似文献   

Importance of soil surface characteristics on water erosion in a small grazed Sahelian catchment     

H. Karambiri  O. Ribolzi  J. P. Delhoume  J. Ducloux  A. Coudrain‐Ribstein  A. Casenave 《水文研究》2003,17(8):1495-1507

This study concerns the problem of water erosion in the Sahel. Surface water and sediment yields (suspended matter and bedload) were monitored for 3 years (1998–2000) at the outlet of a small grazed catchment (1·4 ha) in the northern part of Burkina Faso. The catchment consists of about 64% sandy deposits (DRY soil surface type), which support most of the vegetation, and about 34% of crusted bare soils (ERO soil surface type). The annual solid‐matter export is more than 90% suspended sediment, varying between 4·0 and 8·4 t ha^?1. The bedload represents less than 10% of soil losses. In a single flood event (10 year return period), the sediment yield can reach 4·2 t ha^?1. During the period studied, a small proportion (20 to 32%) of the floods was thus responsible for a large proportion (80%) of the solid transport. Seasonal variation of the suspended‐matter content was also observed: high mean values (9 g l^?1) in June, decreasing in July and stabilizing in August (between 2 and 4 g l^?1). This behaviour may be a consequence of a reorganization of the soil surfaces that have been destroyed by trampling animals during the previous long dry season, vegetation growth (increase in the protecting effect of the herbaceous cover) and, to a lesser extent, particle‐supply limitation (exhaustion of dust deposits during July). The particle‐size distribution in the suspended matter collected at the catchment outlet is 60% made up of clay: fraction ≤2 µ m. The contribution of this clay is maximum when the water rises and its kaolinite/quartz ratio is then close to that of the ERO‐type surfaces. This indicates that these surfaces are the main source of clay within the catchment. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

RXTE observations of the transient sources IGR J17091-3624 and IGR J18539+0727     

A. A. Lutovinov  M. G. Revnivtsev 《Astronomy Letters》2003,29(11):719-723

We present the results of our analysis of the RXTE observations for two transient sources, IGR J17091-3624 and IGR J18539+0727, in April 2003. The derived energy spectra of the sources and the power-density spectra of their light curves make it possible to classify them as low/hard-state X-ray binaries. The parameters of the power spectrum for IGR J18539+0727 lead us to tentatively conclude that the compact object in this binary is a black hole.  相似文献   

山东省昌乐县新生代火山口新发现及旅游地质意义   总被引：4，自引：0，他引：4       下载免费PDF全文

王胜源  刘明渭  梁邦启  宋万千  张军  杨向东  杜崇林 《山东国土资源》2003,19(4):48-50

昌乐蓝宝石闻名遐尔，但蕴藏蓝宝石的火山岩及火山群却少有人知。昌乐县境内几十个由新近纪临胸群牛山组尧山组玄武岩构成的山包，大都是古火山口(颈)。近期，在北岩镇南开出的古火山口(颈)，其玄武岩柱状节理的扇状展布和罕见的两次熔岩喷发交切遗迹，比以往已开发的乔官镇团山子古火山口更为奇特和壮观。火山地貌景观区历来是人们向往的旅游胜地，对昌乐古火山群旅游资源，应加大开发和保护力度，使其尽快成为人们观赏地质奇观、增长科学知识的基地。发展地质旅游将促进当地经济的腾飞。  相似文献   

射电天球参考架指向维持方法讨论     

李金岭  金文敬  李金增 《天文研究与技术》1994,(4)

依据河外射电源天球参考架的现状与建立射电天球参考架的最终目的，本文提出了以共同基本源维持参考架指向的观点。对实际资料的归算结果表明，在确保参考架指向长期稳定性方面，共同基本源指向维持模型优于ＩＥＲＳ维持模型。依据验算结果，文中同时讨论了选源标准与参考架指向稳定性的关系，指出基本源一次性变更的比例不能过高。一方面应完善选源标准；另一方面，一旦此标准发生性？上的改变时，应对在旧标准下选出的基本源进行复核，并作相应的指向调整，否则将可能造成参考架指向的跳变。  相似文献   

浙西北前震旦纪火山岩的Nd、Sr同位素地球化学     

徐步台 《浙江国土资源》1994,(2)

在浙西北双溪坞群和上墅组火山岩系获得较可靠的Sm－Nd同位素年龄的基础上，本文进一步做了Nd、Sr同位素地球化学研究。∈Nd（T）和∈Sr（T）示踪判别了该区前震旦纪火山岩浆源区特征及其物质来源。同时，Nd同位素模式年龄为该区存在更古老基底提供了重要的地质年代信息。  相似文献   

The universal luminosity function of binary X-ray sources in galaxies     

K. A. Postnov 《Astronomy Letters》2003,29(6):372-373

The empirically found universal power-law form of the X-ray luminosity function for a population of high-mass X-ray binaries in galaxies can be explained by the fundamental mass-luminosity and mass-radius relations for massive stars.  相似文献   

Search for groups of extragalactic radio sources     

A. G. Gubanov  A. I. Kopylov  A. S. Potapov 《Astronomy Letters》2003,29(4):224-235

We explore the possibility of searching for groups of radio sources from the FIRST catalog on angular scales 1′–5′. We developed an efficient method of searching for such groups that takes into account the need for combining the components of extended sources represented in the catalog by separate objects. We found 31 groups of radio sources with angular sizes <5′ that contain no fewer than five sources with flux densities ≥3 mJy. This number is at least triple the expected number of such groups for a random Poisson distribution of radio sources in the sky. The prospects for using groups of radio sources to detect and study distant systems of galaxies are discussed.  相似文献   

Broadband X-ray spectrum of XTE J1550-564 during the outburst of 2003     

V. A. Aref’ev  M. G. Revnivtsev  A. A. Lutovinov  R. A. Sunyaev 《Astronomy Letters》2004,30(10):669-674

We present the INTEGRAL and RXTE X-ray observations of XTE J1550-564, a Galactic microquasar and a black hole candidate, during its outburst in the spring of 2003. The source during the outburst was in a canonical hard state, and its spectrum remained constant in both the rise and decay phases.  相似文献