HD 172189, a Cluster Member Binary System with a δ Scuti Component in the Field of View of COROT     

Pedro J. Amado  Susana Martín-Ruíz  Juan Carlos Suárez  Armando Arellano Ferro  Andrés Moya  Ignasi Ribas  Ennio Poretti 《Astrophysics and Space Science》2006,304(1-4):173-175

Photometric and spectroscopic results for the star HD 172189, member of the open cluster IC 4756 in the summer field of the space mission COROT, are presented. From photometric observations in the Strömgren system carried out at various epochs, its binary nature as well as the presence of a δ Scuti-type pulsating component have been discovered. The frequency analysis of the whole dataset confirms a dominant frequency of 19.5974 c d^?1 with a maximum amplitude near 0.02 mag plus other frequencies in the range 18–20 c d^?1. A preliminary orbital solution from the light curve and from four FEROS spectra reveals two similar components of around 1.5 M _⊙ orbiting with a period of 5.702 d.  相似文献   

Another interpretation of the power-law-type spectrum of an ultraluminous compact X-ray source in IC 342     

A. Kubota  C. Done  K. Makishima 《Monthly notices of the Royal Astronomical Society》2002,337(3):L11-L15

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Open clusters IC 4665 and Cr 359 and a probable birthplace of the pulsar PSR B1929+10     

V. V. Bobylev 《Astronomy Letters》2008,34(10):686-698

Based on the epicyclic approximation, we have simulated the motion of the young open star clusters IC 4665 and Collinder 359. The separation between the cluster centers is shown to have been minimal 7 Myr ago, 36 pc. We have established a close evolutionary connection between IC 4665 and the Scorpius-Centaurus association — the separation between the centers of these structures was ≈200 pc 15 Myr ago. In addition, the center of IC 4665 at this time was near two well-known regions of coronal gas: the Local Bubble and the North Polar Spur. The star HIP 86768 is shown to be one of the candidates for a binary (in the past) with the pulsar PSR B1929+10. At the model radial velocity of the pulsar V _r = 2 ± 50 km s^?1, a close encounter of this pair occurs in the vicinity of IC 4665 at a time of ?1.1 Myr. At the same time, using currently available data for the pulsar B1929+10 at its model radial velocity V _r = 200 ± 50 km s^?1, we show that the hypothesis of Hoogerwerf et al. (2001) about the breakup of the ζ Oph-B1929+10 binary in the vicinity of Upper Scorpius (US) about 0.9 Myr ago is more plausible.  相似文献   

X-ray source populations in the region of the open clusters NGC 6633 and IC 4756     

K. R. Briggs  J. P. Pye  R. D. Jeffries  E. J. Totten 《Monthly notices of the Royal Astronomical Society》2000,319(3):826-836

Using deep exposures (∼10⁵ s) with the ROSAT High Resolution Imager, we have performed flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources, respectively. Our primary aim is to search for so-far unrecognized cluster members. We propose identifications or classifications (cluster member, field star, extragalactic field object) for the X-ray sources, based on published membership lists, and on X-ray:optical flux ratios and optical colour–magnitude diagrams. Results of simulating the expected X-ray-emitting source populations are compared with the ROSAT measurements and with the expected capabilities of the XMM mission. The simulations provide a novel method of comparing the activity levels of NGC 6633 and IC 4756 with that of the Hyades. The measurements and simulations confirm that cluster members are the major class of X-ray emitter in these fields at flux levels     (0.1–2.4 keV), contributing ∼40 per cent of the total X-ray sources. We find six possible new members in NGC 6633 and four candidates in IC 4756; all require further observation to establish membership probability.  相似文献   

New spectroscopic classifications of 35 chemically peculiar candidate stars     

E. Paunzen  M. Netopil  O.I. Pintado  M. Rode‐Paunzen 《Astronomische Nachrichten》2011,332(1):77-82

The chemically peculiar (CP) stars of the upper main sequence are perfect tracers for several astrophysical processes. Their study especially in open clusters further helps to establish their evolutionary status. The latter is most important to understand the origin and evolution of the CP phenomenon, i.e. the connection between diffusion and a stellar magnetic field. There are two important topics, we cover with this paper. First of all, we investigate the reliability of the CCD Δa photometry for fainter objects in open clusters. The latter method is able to detect CP stars very efficiently, but still a spectroscopic verification is needed to verify the photometric candidates. On the other hand, already published spectral classifications on the basis of photographic plates and prism technology have tobe tested with modern instruments. Classification resolution spectroscopy is presented for thirty five bona‐fide CP candidates. Twenty six of them are located within the boundaries of fourteen open clusters, for which we also investigated their membership probabilities. Apart from five objects, they seem tobe members of the respective clusters. The objects were classified in the framework of a refined Morgan‐Keenan system with the extension of well established CP star spectra. We confirm the CP nature of all but one target. The results of Δa photometry and the spectral classifications are in excellent agreement. For the cluster members we find a continuous sequence of CP stars from 10 to 850 Myr, the whole range of investigated cluster ages (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

北京及其周边地区闪电活动的时空特征   总被引：3，自引：2，他引：1       下载免费PDF全文

李京校  宋海岩  肖稳安  杜晓宾  郭凤霞 《大气科学学报》2013,36(2):235-245

利用具有总闪观测能力的SAFIR3000在2005-2007年对北京及周边地区(天津、唐山、廊坊等)的观测资料,分析了该地区云闪和地闪时空分布特征.结果表明:云闪高发时段在15:00-次日00:00,峰值在19:00,高发月份在6-8月,峰值在7月;云闪空间分布高值区在北京东北部、天津北部、承德西南部一带,约为30次/(km2·a);云闪平均高度(海拔高度)日变化差异不大,季节变化夏季最高,冬季最低;高度在9～10 km的云闪最多,占云闪总次数的10.97％.地闪高发时段、月份、地闪高值区(密度约为5次/(km2·a))与云闪基本相似,不同之处在于云闪日分布多为单峰,而地闪为双峰,云闪高值时段开始与结束时间均比地闪早;云闪空间分布高值区密度约为地闪的6倍.3 a平均正闪占地闪总数百分比为16.44％,夏季该百分比较低,春秋季较高,其月际变化与正闪次数月际变化相反.总闪时空分布特征和云闪更为相似,总闪高值区分布和卫星探测得到的基本一致.  相似文献   

一种精确的非挥发性存储器中高压产生系统的稳定性分析模型     

姜丹丹  杨燕  曹华 《成都信息工程学院学报》2014,29(3):222-226

针对高压产生系统在非挥发性存储器中的重要作用,推导出一个用于电流模DC-DC升压转换器稳定性分析的精确模型。该模型综合了传统的脉冲宽度调制模型的简洁性以及离散时间采样系统的精确性,得到一个精确的、具有较强指导意义的传输函数模型。同时,根据推导的结果搭建了一个简洁、直观的仿真电路模型。通过此传输函数模型以及仿真电路模型,可以方便快捷的分析、仿真得到电路中的每一个参数对转化器的增益、电流环稳定性、右半平面零点、输出极点的影响。所介绍的方法也可以直接用于其他DC-DC转化器传输函数的推导。  相似文献   

Triggered star formation in expanding shells     

S.Ehlerová  J.Palou&#; 《Monthly notices of the Royal Astronomical Society》2002,330(4):1022-1026

We discuss fragmentation processes which induce star formation in the dense walls of expanding shells. We test the influence of the energy input, the interstellar medium scaleheight and the speed of sound in the ambient medium, and formulate the condition for the gravitational fragmentation of expanding shells: if the total surface density of the disc is higher than a certain critical value, the shells are unstable. The value of the critical density depends on the energy of the shell and the sound speed in the interstellar medium.  相似文献   

Detailed kinematic study of the ionized and neutral gas in the complex of star formation in the galaxy IC 1613     

T. A. Lozinskaya  A. V. Moiseev  N. Yu. Podorvanyuk 《Astronomy Letters》2003,29(2):77-90

We carried out detailed kinematic studies of the complex of multiple H I and H II shells that represent the only region of ongoing star formation in the dwarf irregular galaxy IC 1613. We investigated the ionized-gas kinematics by using Fabry—Perot Hα observations with the 6-m Special Astrophysical Observatory telescope and the neutral-gas kinematics by using VLA 21-cm radio observations. We identified three extended (300–350 pc) neutral shells with which the brightest H II shells in the complex of star formation are associated. The neutral-gas kinematics in the complex has been studied for the first time and the H I shells were found to expand at a velocity of 15–18 km s^?1. We constructed velocity ellipses for all H II shells in the complex and refined (increased) the expansion velocities of most of them. The nature of the interacting ionized and neutral shells is discussed.  相似文献   

A triple nucleus in the brightest cluster galaxy in Abell 193     

Marc S. Seigar  Paul D. Lynam  Nicole E. Chorney 《Monthly notices of the Royal Astronomical Society》2003,344(1):110-114

We present a ground-based, near-infrared, K -band image and a Hubble Space Telescope ( HST ) WFPC2 image of the brightest cluster galaxy in Abell 193 (IC 1695). This object was selected as the central cluster galaxy using X-ray information. Both images reveal a triple nucleus structure. Previously, this galaxy was thought to have only two nuclei. We present colours and magnitudes and a colour plot of the three nuclei. The nuclear structure and colours of the nuclei in this galaxy suggest that a merger may have taken place in its recent history.  相似文献