激变变星及相关天体的Hα与近红外电离钙三重线的光谱分析

给出了１９９７年４月１５日至１７日在北京天台用２．１６ｍ望远镜卡焦光谱仪观测获得的６颗激变变星（ＡＢ Ｂｏｏ,ＵＸ ＵＭａ,Ｔ ＣｒＢ,ＡＨ Ｈｅｒ,Ｚ Ｃａｍ和Ｖ４２６ Ｏｐｈ）及３颗相关天体（ＵＭａ３,ＥＧ ＵＭａ和Ｌｅｏ３）的ＣＣＤ光谱,并同时拍摄了５颗晚型星（３Ｄｒａ,ｖ Ｖｉｒ,ψＬｅｏ,３４Ｂｏｏ和３６Ｃｏｍ）的ＣＣＤ光谱,作为晚型星参考谱,测量了观测样本星的Ｈα和近红外ＣａⅡ的三重     

7个ROSAT源被证认为激变变星

1990年6月发射的ROSAT卫星完成了全天的X射线巡天观测,得到了包括18811个X射线源的ROSAT全天巡天亮源表（RASS－BSC）。通过对ROSAT亮X射线源不学对应体的证认,我们已经发现了7个激变变星,给出了这7个激变变星的低色散光谱,并根据它们的光谱特征及其它性质进行了讨论。     

激变变星中的白矮星

仅在过去的10年中,由于采用了地面和空同时的光谱观测激变变星中正处于吸积过程的白矮星,在激变变星（CV）的研究方面出现了全新的途径。这些光谱探测开拓了恒星包层、角动量团儿CV演化中吸积物理学研究的新前没中。这篇评论包括了激变变星中的白矮星研究的方方面面：（1）表面温度;（2）吸积加热和冷却的不;(3)在高度倾斜的CV中吸收幕帘（盘的上面的大气）的影响和特点;（4）白矮星光球的化学丰度;（6）吸积带;（7）吸积的模拟。     

短周期激变变星周期分布的新统计

我们对周期小于周期分布空缺段的激变变星，重新进行了周期分布统计，使用了比Ｗａｒｎｅｒ等人更多，更新的资料，统计中发现一个ＡＭＨｅｒ型ＣＶｓ：ＧＲＵＶ１偏离了Ｗａｒｎｅｒ等人的统计结果，我们给出了ＣＶＳ新的周期分布图和相应于此分布的随机概率。虽然结果与Ｗａｒｎｅｒ等人的不同，但周期分布同磁场仍呈现一定的相关性，磁激变变星与非磁激变变星同样显示出成团趋势。     

激变变星0623＋71的光谱研究

本文提出了激变变星０６２３十７１的４个时间分辨光谱，覆盖轨道周期的７３％．其中的３个谱清楚地显示了各种光谱特征随轨道运动的变化，在流量、能谱以及谱线轮廓方面的这种变化正是对一个倾角不太大的激变变星所期望的．然而另一个曝光对分钟的谱，流量和视向速度与预期的相比都太大，很难加以解释，可能它是一次象ＡＥＡｑｒ中观测到的跃发事件．     

PG激变星候选天体的光变曲线

我们于1989年用北京天文台兴隆观测站的60/90/180厘米施密特望远镜及Thomson红敏CCD对14个PG候选激变变星进行光度观测.其光变曲线特性表明:PG0027+260,PG0818+513,和PC1030+590为激变食变星,PG1341—079 是一个可能的激变食变星,PG1551+719为SU UM_a型矮新星,此外还有6个天体的光变曲线有激变星特有的闪变特征.因此PG样本中,激变变星的成功率为79％.PG1030+590的轨道周期为3~h279,PG1717+413的闪变变幅在二个月内有明显变化,它与本身的亮度无明显相关,说明闪变变幅的变化可能是亮斑的局部效应.     

间隙时间序列谱分析方法的检验及其在激变变星短周期振荡分析中的应用

本文对具有或长或短间隙（gap）的时间序列的谱分析方法进行研究，给出递推公式，并且用模拟信号进行检验，证实这个方法的可靠性．并把它应用到激变变星V795Her和激变前变星HWVir的短周期振荡分析中，结果表明这两颗变星都有明显的闪变，在V795Her中还存在周期为265.91s和116.70s的振荡．     

晚型星计算机自动光谱分类

在对恒星形成区（ＳＦＲ）中ＲＯＳＡＴ选弱发射线ＴＴａｕｒｉ星（ＷＴＴＳ）进行光谱证认的过程中,发展了一套基于北京天文台２．１６米光学望远镜及其ＯＭＲ卡焦光谱仪系统的晚型星中色散（５０Ａ／ｍｍ）光谱计算机自动光谱分类方法．对ＲＯＳＡＴ选ＷＴＴＳ候选作中晚型星进行自动光谱分类的结果表明,一般情况下,光谱型的分类精度可达±１个次级,个别源为±２个次级．该自动光谱分类方法同时适用于其他光谱晚型星．     

我国近年来天文的新发现

这里叙述的新发现仅指某一特殊类型的发现（如新星，超新星和小行星等）及某一特殊类型天体的认证（如X射线源证认为类星体等），而不包括某一类天体的某种天象及未知性质源的列表（如深度成像观测得到的前人没有纪录过的一般天体，如恒星，但一些特殊天体亦列入），由于收集不全面和所谓“发现”定义的困难，向有发向而未列入者先歉意。从80年代后期开始，我国的观测设备有了很大垢发展，所以有一批重的的天文发现，为天文提供了很好的机会，它包括下面几方面，层系层次天体：（1）用X射线源和射电源证认了一批包括类星体，BL Lac天体，赛弗特天体在内的活动星系核；（2）用IRAS源证认了一批W－R星系；（3）BATC巡天在一个星系周围发现了一个“环”。恒星层次天体：（1）河外星系中发现了一批超新星的一个新星，（2）发现了和用ROSAT源证认了一批激变变星，（4）BATC和超新星巡天发现了一批变星，（4）发现了若干新的δSct变星，（5）发现了一批Herbig-Haro天体，（6）发现了一批水脉泽。行星层次天体：（1）发现了大批小行星，特别是有些是近地不行星，（20发现若干彗星。     

晚型星计算机自动光谱分类

在对恒星形成区（ＳＦＲ）中ＲＯＳＡＴ选弱发射线Ｔ Ｔａｕｒｉ星（ＷＴＴＳ）进行光谱证认的过程中,发展了一套基于北京天台２．１６米光学望远镜及其ＯＭＲ卡焦光谱仪系统的晚型星中色散（５０Ａ／ｍｍ）光谱计算机自动光谱分类方法。对ＲＯＳＡＴ选ＷＴＴＳ候选体中晚型星进行自动光谱分类的结果表明,一般情况下,光谱型的分类精度可达±１个次级,个别源为±２个次级。该自动光谱分类方法同时适用于其它光谱晚型星。     

A thermodynamic model of high temperature lava vaporization on Io

We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the ONaKFeSiMgCaAlTi system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B1 Ca, Al-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for Io's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match Io's atmospheric Na/K ratio of 10±3 reported by Brown (2001, Icarus 151, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl₂, MgS, MgCl, FeCl₂, FeS, FeCl, and SiS.     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages).Authors who submit a paper are expected to be able to certify that the paper is original work,     

Alkali and halogen chemistry in volcanic gases on Io

We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10⁻⁶ to 10⁺¹ bars) ranges, which overlap the nominal conditions at Pele (T=1760 K, P=0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. The elemental abundances for O, S, Na, K, and Cl are based upon observations. CI chondritic elemental abundances relative to sulfur are used for the other alkalis and halogens (as yet unobserved on Io). We predict the major alkali species in Pele-like volcanic gases and the percentage distribution of each alkali are LiCl (73%), LiF (27%); NaCl (81%), Na (16%), NaF (3%); KCl (91%), K (5%), KF (4%); RbCl (93%), Rb (4%), RbF (3%); CsCl (92%), CsF (6%), Cs (2%). Likewise the major halogen species and the percentage distribution of each halogen are NaF (88%), KF (10%), LiF (2%); NaCl (89%), KCl (11%); NaBr (89%), KBr (10%), Br (1%); NaI (61%), I (30%), KI (9%). We predict the major halogen condensates and their condensation temperatures at P=0.01 bar are NaF (1115 K), LiF (970 K); NaCl (1050 K), KCl (950 K); KBr (750 K), RbBr (730 K), CsBr (645 K); and solid I₂ (200 K). We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. Their estimated photochemical lifetimes range from a few minutes for alkali iodides to a few hours for alkali fluorides. Condensation is apparently the only loss process for elemental iodine. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observations of brown dwarfs we also recommend a search of Io's extended atmosphere and the Io plasma torus for neutral and ionized Li, Cs, Rb, and F.     

The climatic and physiographic controls of the eastern Mediterranean over the late Pleistocene climates in the southern Levant and its neighboring deserts

Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr^− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant.     

Active hot star shells

Interferometry in the visible provides milliarcsecond spatial resolution and thus has been used for studying the circumstellar environment of active hot stars. In this paper I will illustrate how the visibility modulus and phase can be used to better constrain the physics of Be disks through results from the VLA, the MkII and the GI2T interferometers. I will insist on the importance and the potential of coupling high angular resolution with high spectral resolution to the study of Be shells. Finally I will present a possible study of the circumstellar disk of Be stars using the VLTI. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fitting X-ray Afterglow Light curves of Gamma-ray Bursts by Using the Magnetar Energy Injection Model

The central compact object for some gamma-ray bursts (GRBs) may be a strongly magnetized millisecond pulsar. It can inject energy to the outer shock of the GRB by through the magnetic dipole radiation, and therefore causes the shallow decay of the early afterglow. Recently, from a large number of GRB X-ray afterglows observed by Swift/XRT(X-ray telescope), it is revealed that many of them exhibit the shallow decay about 10²∼10⁴ s after the burst prompt emission. We have fitted the X-ray afterglow light curves of 11 GRBs by using the energy injection model of a magnetar with the rotation period in the millisecond order of magnitude. The obtained result shows the validity and universality of the magnetar energy injection model in explaining the shallow decay of afterglows, and simultaneously provides some constraints on the magnetic field strength and rotation period of the central magnetar.     

Born–Infeld type phantom model in the ω–ω′ plane

In this paper, we investigate the dynamics of Born–Infeld (B–I) phantom model in the ω–ω′ plane, which is defined by the equation of state parameter for the dark energy and its derivative with respect to N (the logarithm of the scale factor a). We find the scalar field equation of motion in ω–ω′ plane, and show mathematically the property of attractor solutions which correspond to ω _φ ∼−1, Ω _φ =1, which avoid the “Big rip” problem and meets the current observations well.      

Shear and vorticity in a combined Einstein-Cartan-Brans-Dicke inflationary lambda-Universe

A combined BCDE (Brans-Dicke and Einstein-Cartan) theory with lambda-term is developed through Raychaudhuri’s equation, for inflationary scenario. It involves a variable cosmological constant, which decreases with time, jointly with energy density, cosmic pressure, shear, vorticity, and Hubble’s parameter, while the scale factor, total spin and scalar field increase exponentially. The post-inflationary fluid resembles a perfect one, though total spin grows, but the angular speed does not (Astrophys. Space Sci. 312: 275, 2007d).