Blazar天体的辐射特性研究

收集了47个Blazar天体的短时标光变资料,估算了中心天体质量和不同波段辐射区域,并对估算结果作了统计分析,发现Blazar天体中心黑洞质量在10~7M_☉到10~(10)M_☉之间,BL Lac天体与平谱射电类星体中心黑洞质量有很大差异,平谱射电类星体中心黑洞质量大于BL Lac天体中心黑洞质量;红外波段和γ射线波段辐射区域大小相似.同时,利用收集到Blazar天体的热光度分析了Blazar天体热光度与短时标光变之间的关系,证实了射电选BL Lac(RBL)天体和平谱射电类星体(FSRQs)的辐射是强成束的,但相对论聚柬效应对X射线选BL Lac(XBL)天体的辐射影响较小.     

费米耀变体喷流功率与多波段光度的相关性研究

耀变体的喷流辐射机制是一个非常重要的问题。从文献中收集了442个耀变体的数据,这些耀变体包括215个平谱射电类星体(Flat Spectrum Radio Quasars, FSRQ)和227个蝎虎天体(BL Lac),通过数据研究了耀变体的喷流功率与多波段光度的相关性。研究结果表明:(1)对于平谱射电类星体,喷流功率与射电波段、光学波段、X射线和γ射线的光度都有强相关性,且光度分布顺序为logL_γ logL_O logL_X logL_R。(2)对于蝎虎天体,喷流功率与射电波段、光学波段和γ射线的光度都有强相关性,但是喷流功率与X射线的光度只有弱相关性;蝎虎天体的光度分布顺序为logL_O logL_γ logL_X logL_R,而且蝎虎天体的各波段光度都小于平谱射电类星体。我们认为这些差异是由于平谱射电类星体与蝎虎天体的内禀属性不同导致的,即吸积模式不同和喷流辐射机制不同等。     

特殊BL Lac型天体的VLBI观测研究

BL Lac型天体是一类特殊的活动星系核,根据辐射能谱的不同可以分为低峰值频率BL Lac型天体(LBLs),中间峰值频率BL Lac型天体(IBLs),高峰值频率BL Lac型天体(HBLs),以及极高峰值频率BL Lac型天体(UHBLs)。不同类型BL Lac型天体具有不同的辐射特性,通过射电、光学、X射线、伽玛射线等多波段的观测可以发现很多特殊类型及辐射特性的BL Lac型天体,而甚长干涉测量技术(Very Long Baseline Interferometry,VLBI)是目前分辨率最高的观测技术,也是探测致密核区结构的唯一手段。主要介绍目前对BL Lac型天体的VLBI观测研究概况,以及对其中一些特殊BL Lac型天体VLBI研究的进展及初步结果。     

射电选和X射线选BL Lacertae天体的射电性质

收集了射电选和X射线选BL Lac天体的射电数据(包括核和延展光度), 并计算了它们的核主导系数R.研究显示: 射电选BL Lac(RBLs)天体的总射电光度是X射线选BL Lac(XBLs)天体的2个量级.详细分析得到这种差别主要是来自于核光度的差别因为延展光度差别只有1个量级.研究RBLs和XBLs的核(延展元)光度与核主导系数之间的关系, 发现延展元光度与核主导系数负相关, 而核(总)光度几乎与核主导系数没有相关.     

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.     

X射线选射电噪活动星系核的多波段性质(英文)

基于被ROSAT全天区巡天观测和射电 4.85GHz巡天观测同时探测到的活动星系核的大样本 ,研究了X射线选的射电噪活动星系核的多波段性质 .通过分析该样本中的活动星系核的宽波段能量分布 ,确认了来自射电、光学和X射线波段的辐射光度之间的显著相关性 .这种相关性对于类星体、赛弗特、蝎虎座天体和射电星系是有区别的 .同时 ,探讨了从光学到X射线波段之间的谱指数与红移以及 50 0 0 和 4.85GHz处的单色光度的相关性     

X线选射电噪活动星系核的多波段性质

基于被ROSAT全天区巡天观测和射电4．85GHz巡天观测同时探测到的活动星系核的大样本,研究了X射线选的射电噪活动星系核的多波段性质．通过分析该样本中的活动星系核的宽波段能量分布,确认了来自射电、光学和X射线波段的辐射光度之间的显著相关性．这种相关性对于类星体、赛弗特、蝎虎座天体和射电星系是有区别的．同时,探讨了从光学到X射线波段之间的谱指数与红移以及5000A和4．85GHz处的单色光度的相关性．     

费米耀变体的X射线辐射

耀变体(blazar)的X射线辐射位于同步辐射的尾部及逆康普顿辐射的前部分,因此其辐射起源较为复杂.耀变体从射电到X射线波段辐射的谱能分布(SED)可用抛物线函数近似拟合.若将该拟合所得拟合曲线近似视为耀变体的物理谱,分析费米(Fermi)耀变体的X射线辐射,则结果表明:耀变体的X射线辐射包含同步辐射和逆康普顿辐射2个成份,并可用该拟合线将X射线的同步辐射和逆康普顿辐射成份进行简单分离;源的同步峰频越高,其同步辐射成份越多,而其逆康普顿辐射成份越少;在X射线1 keV处,对于平谱射电类星体(FSRQ)、低同步峰BL Lac天体(LBL)和高同步峰BL Lac天体(HBL),其同步辐射成份占总辐射的比例分别为17%、27%和73%;同步峰频与X射线1 keV处同步辐射流量密度有强正相关,而与逆康普顿辐射流量密度无相关;在X射线波段,LBL的辐射机制与FSRQ的类似.     

Fermi耀变体的gamma射线多波段辐射与射电辐射的关系

从Fermi 3期源表(3FGL)中选择了一个含935个耀变体(blazar)的样本, 包括415个平谱射电源(Flat Spectrum Radio Quasar, FSRQ), 520个蝎虎天体(BL Lac object, BL Lac), 其中高同步峰BL Lac (HBL) 233个, 中同步峰BL Lac (IBL) 144个, 低同步峰BL Lac (LBL) 143个. 研究了总样本、FSRQ、BL Lac及其子类HBL、LBL的射电1.4GHz 与gamma射线在0.1、0.3、1、3、10GeV处辐射流量密度的关系. 结果显示: 所有样本的射电1.4GHz与5个波段gamma射线的辐射流量都有强相关, 相关系数在0.48--0.81之间, 机会概率均小于$10^{-4; 对于不同的样本相关系数随着gamma射线辐射频率的变化有不同的变化趋势, 所有样本在5个波段的相关系数平均值随gamma射线频率的增加而减小. 该结果暗示, 随着频率的升高, blazar的gamma射线辐射主导机制在发生变化, 在相同频率处, 不同类型天体的辐射主导机制存在差异; HBL的gamma射线辐射主要由同步自康普顿主导, 而LBL的其他成份比HBL的更复杂; FSRQ的gamma射线起源较BL Lac的复杂.     

Fermi耀变体的γ射线多波段辐射与射电辐射的关系

从Fermi 3期源表(3FGL)中选择了一个含935个耀变体(blazar)的样本,包括415个平谱射电源(Flat Spectrum Radio Quasar, FSRQ), 520个蝎虎天体(BL Lac object, BL Lac),其中高同步峰BL Lac (HBL) 233个,中同步峰BL Lac (IBL) 144个,低同步峰BL Lac (LBL) 143个.研究了总样本、FSRQ、BL Lac及其子类HBL、LBL的射电1.4 GHz与γ射线在0.1、0.3、1、3、10 GeV处辐射流量密度的关系.结果显示:所有样本的射电1.4 GHz与5个波段γ射线的辐射流量都有强相关,相关系数在0.48–0.81之间,机会概率均小于10~(-4);对于不同的样本相关系数随着γ射线辐射频率的变化有不同的变化趋势,所有样本在5个波段的相关系数平均值随γ射线频率的增加而减小.该结果暗示,随着频率的升高, blazar的γ射线辐射主导机制在发生变化,在相同频率处,不同类型天体的辐射主导机制存在差异; HBL的γ射线辐射主要由同步自康普顿主导,而LBL的其他成份比HBL的更复杂; FSRQ的γ射线起源较BL Lac的复杂.     

Radiative association of C and P, and Si and P atoms

The rate coefficients for the formation of carbon monophosphide (CP) and silicon monophosphide (SiP) by radiative association are estimated for temperatures ranging from 300 to 14 100 K. In this temperature range, the radiative association rate coefficients are found to vary from  1.14 × 10⁻¹⁸  to  1.62 × 10⁻¹⁸ cm³ s⁻¹  and from  3.73 × 10⁻²⁰  to  7.03 × 10⁻²⁰ cm³ s⁻¹  for CP and SiP, respectively. In both cases, rate coefficients increase slowly with the increase in temperature.     

DDO photometry and metallic abundances of E and SO galaxies and globular clusters of the LMC and SMC

Metallicity of 8 E and SO galaxies as well as that of red globulars of the LMC and SMC were obtained by means of DDO integrated photometry calibrated with galactic globular clusters (Bica and Pastoriza, 1983; hereafter referred to as Paper I). A correction was obtained in order to reduce the colors of the galaxies to zero redshift. The relation metallicity vsM _V for the galaxies is analyzed (adding to our sample the observations of McClure and Van den Bergh, 1968; and Faber, 1973a). For the Magellanic Clouds we found metallicity ranging from intermediate to poor.     

Uranus and Neptune: Shape and rotation

Both Uranus and Neptune are thought to have strong zonal winds with velocities of several 100 m s⁻¹. These wind velocities, however, assume solid-body rotation periods based on Voyager 2 measurements of periodic variations in the planets’ radio signals and of fits to the planets’ magnetic fields; 17.24 h and 16.11 h for Uranus and Neptune, respectively. The realization that the radio period of Saturn does not represent the planet’s deep interior rotation and the complexity of the magnetic fields of Uranus and Neptune raise the possibility that the Voyager 2 radio and magnetic periods might not represent the deep interior rotation periods of the ice giants. Moreover, if there is deep differential rotation within Uranus and Neptune no single solid-body rotation period could characterize the bulk rotation of the planets. We use wind and shape data to investigate the rotation of Uranus and Neptune. The shapes (flattening) of the ice giants are not measured, but only inferred from atmospheric wind speeds and radio occultation measurements at a single latitude. The inferred oblateness values of Uranus and Neptune do not correspond to bodies rotating with the Voyager rotation periods. Minimization of wind velocities or dynamic heights of the 1 bar isosurfaces, constrained by the single occultation radii and gravitational coefficients of the planets, leads to solid-body rotation periods of ∼16.58 h for Uranus and ∼17.46 h for Neptune. Uranus might be rotating faster and Neptune slower than Voyager rotation speeds. We derive shapes for the planets based on these rotation rates. Wind velocities with respect to these rotation periods are essentially identical on Uranus and Neptune and wind speeds are slower than previously thought. Alternatively, if we interpret wind measurements in terms of differential rotation on cylinders there are essentially no residual atmospheric winds.     

Radii and Albedos of four Trojan asteroids and Jovian satellites 6 and 7

Thermal radiation has been detected from four asteroids of the Trojan group, and J6 and J7, the brightest of the outer satellites of Jupiter. The six objects all have exceedingly low geometric albedos of 0.02 or 0.03 according to calculations based on their known visual brightness and the measured thermal fluxes. 624 Hektor, the largest object studied here, has a radius of 110 ± 20 km, though the exact shape of this body is in question. While the sample observed in this work is small (the total number of Trojans larger than 0.25 km in radius is about 1000), the fact that all four studied have similarly low albedos suggests that this property is characterisic of the Trojans and at least two of the outer members of Jupiter's retinue of satellites. The low surface albedo of the Trojans may preclude the proposed origin of the Jovian group of comets among these bodies according to E. Rabe. Updated tables of the dimensions of all the Jovian satellites are given.     

Substructure and the cusp and fold relations

Gravitational lensing of a background source by a foreground galaxy lens occasionally produces four images of the source. The cusp and the fold relations impose conditions on the ratios of magnifications of these four-image lenses. In this theoretical investigation, we explore the sensitivity of these relations to the presence of substructure in the lens. Starting with a smooth lens potential, we add varying amounts of substructure, while keeping the source position fixed, and find that the fold relation is a more robust indicator of substructure than the cusp relation for the images. This robustness is independent of the detailed spatial distribution of the substructure, as well as of the ellipticity of the lensing potential and the presence of external shear.     

Gravity and Topography of Moon and Planets

Planetology serves the understanding on the one hand of the solar system and on the other hand, for investigating similarities and differences, of our own planet. While observational evidence about the outer planets is very limited, substantial datasets exist for the terrestrial planets. Radar and optical images and detailed models of gravity and topography give an impressive insight into the history, composition and dynamics of moon and planets. However, there exists still significant lack of data. It is therefore recommended to equip all future satellite missions to the moon and to planets with full tensor gravity gradiometers and radar altimeters.     

Fragmentation and hydration of tektites and microtektites

Abstract— An examination of data collected over the last 30 years indicates that the percent of glass fragments vs. whole splash forms in the Cenozoic microtektite strewn fields increases towards the source crater (or source region). We propose that this is due to thermal stress produced when tektites and larger microtektites fall into water near the source crater while still relatively hot (>1150 °C). We also find evidence (low major oxide totals, frothing when melted) for hydration of most of the North American tektite fragments and microtektites found in marine sediments. High-temperature mass spectrometry indicates that these tektite fragments and microtektites contain up to 3.8 wt% H₂O. The H₂O-release behavior during the high-temperature mass-spectrometric analysis, plus high CI abundances (0.05 wt%), indicate that the North American tektite fragments and microtektites were hydrated in the marine environment (i.e., the H₂O was not trapped solely on quenching from a melt). The younger Ivory Coast and Australasian microtektites do not exhibit much evidence of hydration (at least not in excess of 0.5 wt% H₂O); this suggests that the degree of hydration increases with age. In addition, we find that some glass spherules (with <65 wt% SiO₂) from the upper Eocene clinopyroxene-bearing spherule layer in the Indian Ocean have palagonitized rims. These spherules appear to have been altered in a similar fashion to the splash form K/T boundary spherules. Thus, our data indicate that tektites and microtektites that generally contain >65 wt% SiO₂ can undergo simple hydration in the marine environment, while impact glasses (with <65 wt% SiO₂) can also undergo palagonitization.     

Local solar magnetic and velocity field development and related photospheric and chromospheric activity

We have compiled the results of our long-term studies of the local magnetic field and its activity development, derived from investigating sunspot group evolution, photoelectrically measured longitudinal magnetic and velocity fields, and measurements of sunspot proper motions. We estimate certain regularities according to which the magnetic and velocity fields, and photospheric, as well as chromospheric activities develop. We speculate about the physical background of such processes.Dedicated to Cornelis de Jager