云南天文台一九九六年度学术论文汇总、上报中科院成果、鉴定成果及获奖项目

云南天文台一九九六年度学术论文汇总、上报中科院成果、鉴定成果及获奖项目一、发表论文：（共１０６篇）１、国际著名刊物（共１３篇）１）Ｂｌａｚａｒ天体的Ｘ－射线谱指数及－γ射线谱指数之间的关系＝ＳｐｅｃｔｒａｌＲｅｌａｔｉｏｎＢｅｔｗｅｅｎＸ－Ｒａｙｓａ...     

BL Lac天体的γ射线和X射线辐射研究

收集了18个γ射线噪BL Lac天体的X射线流量密度和γ射线流量密度,以及X射线波段(1keV)和γ射线波段(＞100 MeV)的平均光谱指数,研究了它们之间的相关性.结果表明:1)X射线流量密度与γ射线流量密度在高态、低态和平均态均有较强的相关性.2)X射线波段和γ射线波段的平均光谱指数之间有较强的负相关性.3)X射线和γ射线波段的平均光谱指数与X射线和γ射线辐射流量密度在高态和平均态时均无显著的相关性.4)γ射线波段的平均光谱指数与X射线辐射流量密度的低态有较强的负相关性.X射线波段的平均光谱指数与γ射线波段的流量密度的低态之间也存在弱相关性.分析结果支持BL Lac天体的X射线和γ射线辐射可能来自同一相对论电子分布的同步辐射和同步自康普顿(SSC)辐射.     

BL Lac 天体的γ射线辐射

活动星系核的γ射线辐射机制仍然是一个待解决的问题,BLLac天体是活动星系核的一类。文中选取了22个BLLac天体,用它们的最大值、最小值和平均值研究了在1GeV处γ射线辐射与射电8.4GHz处辐射之间可能存在的关系。主要结果如下:对于最小值而言,γ射线辐射与射电辐射流量密度之间没有相关性存在;对于最大值和平均值而言,它们的流量密度之间有较好的线性相关性;γ射线辐射与射电辐射谱指数之间也有相关性存在。根据研究结果,我们认为γ射线辐射机制主要是同步自康普顿辐射。     

费米甚高能γ射线耀变体谱指数、能谱峰值频率和能谱曲率相关性研究

收集了69个费米甚高能γ射线(TeV)耀变体样本的平均态多波段数据,并用对数抛物线模型(The Log-parabolic Model)对能谱分布(The Spectral Energy Distribution, SED)进行拟合,获得相关物理参数。分别对谱指数、能谱峰值频率、能谱曲率3个物理参数进行统计分析,结果如下:(1)高峰频蝎虎天体(High-Synchrotron peaked BL Lacertae objects, HBLs)、中峰频蝎虎天体(Intermediate-Synchrotron peaked BL Lacertae objects, IBLs)、低峰频蝎虎天体(Low Synchrotron peaked BL Lacertae objects, LBLs)和平谱射电类星体(Flat Spectrum Radio Quasars, FSRQs)的谱指数分布各异,除射电波段外,样本中蝎虎天体在不同波段谱指数大小呈现高峰频蝎虎天体中峰频蝎虎天体低峰频蝎虎天体的分布规律;(2)样本中蝎虎天体(BL Lacertae objects)的同步辐射能谱的峰值频率和逆康普顿散射能谱的峰值频率之间呈现正相关关系,表明甚高能γ射线蝎虎天体多波段辐射能较好地用同步自康普顿模型解释;(3)通过聚类分析给定高峰频蝎虎天体、中峰频蝎虎天体、低峰频蝎虎天体和平谱射电类星体的能谱曲率分布范围,表明这4类天体样本的能谱曲率分布不同;(4)同步辐射能谱的峰值频率和逆康普顿散射能谱的峰值频率与红外、光学、紫外和软X射线波段的谱指数之间都呈现较强的负相关关系,而同步辐射能谱曲率和除射电波段外的各波段谱指数之间呈现正相关关系;(5)同步辐射能谱的峰值频率和同步辐射能谱曲率之间呈现较强的负相关关系。     

Blazar天体中光学射电大爆发的频谱演化

本文讨论Ｂｌａｚａｒ天体中光学射电大爆发频谱演化的理论模型．考虑沿喷流传播的相对论性激波所注入或加速的相对论性电子，受到康普顿、同步辐射和绝热膨胀三种损耗，并计及相对论电子能谱的高能截断．假定喷流轴线与观测者方向构成很小角度．文中给出了大爆发频谱三阶段连续演化的特性，即康普顿阶段，同步辐射阶段和绝热膨胀阶段的爆发特性．频谱演化用（Ｓｍ－ｖｍ）关系表达（见图２，图中Ｓｍ为频谱反转流量，ｖｍ为反转频率），它与一些Ｂｌａｚａｒ天体中观测到的典型形式相符合．     

γ噪Blazar天体的复合谱指数研究

收集了66个有γ射线噪的Blazar在高态下的多波段流量数据,研究了Blazar复合谱指数之间的相关性.分析了BL Lac天体和平谱射电类星体(FSRQs) 复合谱指数之间的相关性.结果表明(1)高态下Blazar的复合谱指数与αr,ir与αir,γ、αr,ir 与αo,γ、αr,o与αo,x、αr,o与αo,γ之间有强相关性,αr,x与αx,γ之间有强负相关性.(2)平谱射电类星体(FSRQs)在高态下αr,o与αo,x、αr,o与αo,γ有强相关性.(3)BL Lac天体在高态时αr,o与αo,γ之间有强相关性,αr,x与αx,γ、αir,x与αx,γ有强负相关性.(4)γ射线很可能产生于同步自康普顿(SSC)过程.     

AO0235＋164射电波段宽带谱指数周期性变化的研究

收集了AO0235＋164天体射电4．8GHz和14．5GHz波段的光变测量数据,并获得了长期的光变曲线,从光变曲线可以看出其活动是非常剧烈的。利用Jurkevieh方法和自相关函数方法分别对AO0235＋164射电波段宽带谱指数进行周期性分析,并对流量和谱指数进行相关性分析,研究结果表明：（1）AO0235＋164天体射电波段4．8GHz-14．5GHz对应的宽带谱指数,可能存在5．30年的光变周期,与Liu等人用功率谱法在射电波段发现其流量密度可能存在5．59±0．47年的光变周期基本吻合;（2）宽带谱指数与流量密度之间存在相关性。     

Blazars的多波段辐射谱:聚束效应和内禀谱

考虑了观测到的Ｂｌａｚａｒｓ多波段辐射的两分量特征,提出该观测特征可由频率相并的聚束效应和内禀谱一起来解释．多普勒因子与频率之间的关系由分析观测数据获得．假定内禀谱由非均匀喷流中同步－自康普顿机制产生,应用该模型解释了３Ｃ２７９的辐射．     

Blazars的多波段辐射谱：聚束效应和内禀谱

考虑了观测到的Ｂｌａｚａｒｓ多波段辐射的两分量特征,提出该观测特征可由频率相并的取束效应和内禀谱一起来解释。多普勒因子与频率之间的关系由分析观测数据获得。假定内禀谱由非均匀喷流中同步－自康普顿机制产生,应用该模型解释了３Ｃ２７９的辐射。     

BLazar天体的光变及多波段能谱特性

本文综述了活动星系核，特别是blazar天体的研究现状，对blazar天体的多波段与多波段能谱特性研究进行了较为详细的评述。主要的研究工作包括以下内容：（一）γ噪blazar天体的短时标光变研究，通过对16个γ噪blazar天体（其中包括全部已证认和观测到VHEγ射线爆发的可能甚高能γ射线源）自1998年的光学观测及光变分析研究表明，短时标光变（小时量级）是GeV γ噪blazar天体的普遍特性，光变幅度通常可达0.6mag/h，对PKS 1510－089类星体的观测发现在一个小时内对象变暗2个星等，对如此激烈的光变变暗目前的理论还不能很好的解释，但它同样反映了辐射区域的内部结构；而对TBLs的监测表明，其光学波段的短时标光变没有其他对象激烈，出现的频度和振幅变化都较小；（二）在研究γ噪blazar天体光变时，研究了寄主星系对光变的影响，得到了1ES 2344 514的光变与PSF的FWHM的关联，表明随着大气视宁度的下降（即FWHM变大），对象变暗，即由于寄主星系的影响从而导致假光变的产生；（三）引进两个多波段复合谱指数，αXOX=αOX-αX及αoro=αor-αo。对样本的统计研究表明，RBLs是能谱特性界于XBLs和OVVs之间的一类中间态，所得结果支持了Sambruna et al.（1996）大样本多波段能谱分布特性的统计研究结果；（四）对地面探测器对blazar天体甚高能波段的观测做了较为详细的了解，由于blazar天体在全波段上都观测到光变，所以这类对象是多波段观测研究最完全的。地面望远镜对小时量级的光变很敏感，所以，对低流量源的直到10TeV或更高能谱的测量是多波段研究的重要扩展，特别是，如果γ射线的幅射是通过康谱顿散射提升低能同步辐射光子产生的，即SSC模型产生，那么，VHEγ射线的观测和低能同步辐射的观测就可能估计喷流内的磁场强度、Doppler因子等。对我们今后的光学波段的观测工作提出了新的课题。     

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 011 all liranchcs of astronoiriy and astrophysics.Reviews arc by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length     

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.     

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.      

A Comparison of Several Image Locating Algorithms in Astronomical Instruments

In astronomical observations at optical wavelengths, a fast image tracking system can be adopted to reduce the effects of the atmospheric seeing and telescopic tracking error, and therefore improve the observing efficiency. Aiming at the need of astronomical observations, totally 5 kinds of algorithms in two categories were selected to make a comparative study on their accuracies and stabilities under different noise conditions by both numerical experiment and laboratory test. The results indicate that the normalized cross-correlation method and barycenter method have not only a higher accuracy but also a better reliability against interferences, they will be applied to the high-resolution spectrograph of the Xinglong 2.16 m telescope and the scienti?c instruments of the SONG (Stellar Observations Network Group) project, respectively.     

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).      

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.