贺兰山地区云凝结核浓度的测量及分析

利用热扩散型云凝结核计数器在贺兰山地区进行地面和空中云凝结核(CCN)观测。结果表明,在该地区夏季地面平均CCN浓度为610 cm^-3,最大浓度达10⁴ cm^-3。沙尘天气现象没有明显地增加CCN浓度。层状云中CCN浓度随高度变化不大。     

Observations of the gamma-ray flux from the galaxy Mk 501

We present two-year-long observations of the flux of very-high-energy (～10¹² eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies >10¹² eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10^?11 and (3.7±0.6)×10^?11 cm^?2 s^?1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ～2×10⁴³ erg s^?1 sr^?1.     

An ultrasoft X-ray source (RX 215319−1514) and discovery of a narrow‐line Seyfert 1 galaxy

We present results on the identification of the optical counterpart of an ultrasoft X-ray source discovered with ROSAT . Two optical candidates – a galaxy and a star – are found within the error circle of the X-ray source position. Optical spectroscopy of the two candidates reveals that (a) the galaxy is a narrow-line Seyfert type 1 galaxy, and (b) the star is a late A-type or an early F-type. The F _x F _v ratio is too high for the star to be the counterpart of the X-ray source, but consistent with that for an active galaxy. Although higher-resolution X-ray imaging of the region is needed to definitely settle the question of the counterpart of the X-ray source, the narrow-line Seyfert 1 galaxy is the best candidate. The spectral properties of the newly discovered narrow-line Seyfert 1 galaxy are also presented, including its extreme X-ray power-law spectral index of Γ≥4.     

The structure of black hole magnetospheres I. Schwarzschild black holes

We introduce a multipolar scheme for describing the structure of stationary, axisymmetric, force-free black hole magnetospheres in the '3+1' formalism. We focus here on Schwarzschild spacetime, giving a complete classification of the separable solutions of the stream equation. We show a transparent term-by-term analogy of our solutions with the familiar multipoles of flat-space electrodynamics. We discuss electrodynamic processes around disc-fed black holes in which our solutions find natural applications: (i) 'interior' solutions in studies of the BlandfordZnajek process of extracting the rotational energy of holes, and of the formation of relativistic jets in active galactic nuclei and 'microquasars'; (ii) 'exterior' solutions in studies of accretion disc dynamos, disc-driven winds and jets. On the strength of existing numerical studies, we argue that the poloidal field structures found here are also expected to hold with good accuracy for rotating black holes, except for the cases of the maximum possible rotation rates. We show that the closed-loop exterior solutions found here are not in contradiction with the MacdonaldThorne theorem, as these solutions, which diverge logarithmically on the horizon of the hole , only apply to those regions that exclude .     

The black hole mass–galaxy age relation

We present evidence that there is a significant correlation between the fraction of the mass of a galaxy that lies in its central black hole and the age of the galactic stellar population. Since the absorption-line indices that are used to estimate the age are luminosity-weighted, they essentially measure the time since the last significant episode of star formation in the galaxy. The existence of this correlation is consistent with several theories of galaxy formation, including the currently favoured hierarchical picture of galaxy evolution, which predicts just such a relation between the black hole mass and the time since the last burst of merger-induced star formation. It is not consistent with models in which the massive black hole is primordial, and hence uncoupled from the stellar properties of the galaxy.     

Compton-thick X-ray absorption in the Seyfert galaxies Tololo 0109383 and ESO 138G1

We present analyses of the ASCA X-ray spectra of two Seyfert galaxies, Tololo 0109383 and ESO 138G1. In both cases, spectral fitting reveals two statistically acceptable continuum models: Compton reflection and partial covering. Both spectra have strong iron K lines, with equivalent widths greater than 1.5 keV. These large equivalent widths are suggestive of heavier obscuration than that directly indicated by the partial-covering models (  210²³ cm^-2),  with the actual column densities being 'Compton-thick' (i.e.   N _H1.510²⁴ cm^-2).  We use the hard X-ray/[O  iii ] flux correlation for Seyferts and data from the literature to provide additional support for this hypothesis. Since Tololo 0109383 is known to have optical type 1 characteristics such as broad Balmer line components and Fe  ii emission, this result marks it as a notable object.     

Using Hubble Space Telescope images to identify straight segments in galaxy nuclear spirals

This Letter reports the discovery of straight segments of nuclear spiral arms. Hubble Space Telescope images of Seyfert galaxies are used. The morphology of the straight features on scales of few hundred parsecs proves to be similar to the morphology of disc-wide polygonal spirals and rings. This suggests that the straight structures on both nuclear and disc scales may have a common physical nature.     

A new look at the isotropy of narrow-line emission in extragalactic radio sources

We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the 'receding torus' model. We compare these simulations with the known behaviour of the [O  III ] λ5007 and [O  II ] λ3727 emission lines and conclude that [O  III ] is the better indicator of the strength of the underlying non-stellar continuum.     

华北云凝结核分布及与云滴相互作用的观测研究

利用美国DMT公司生产的连续气流单过饱和度云凝结核计数器（DMT—CCN仪）,于2009年4月-7月在华北上空进行云凝结核观测,对不同天气现象下云凝结核的数浓度进行统计分析,研究了云凝结核的垂直分布特征以及水平穿云时云凝结核和云滴的相互作用和演变。     

天津武清地区云凝结核变化特征

利用2009年11—12月在天津武清气象局测量的云凝结核(CCN:Cloud Condensation Nuclei)浓度资料以及气溶胶数谱分布的观测资料,分析了武清地区在不同过饱和度(0.1%～1.0%)下云凝结核浓度及活化率的变化特征。结果表明:武清地区冬季CCN数浓度变化范围很大,过饱和度1%时,浓度变化范围为4000～32000cm-3,且浓度受风速影响明显,风速2级以下CCN数浓度很高,过饱和度1%时,其平均浓度可达16000cm-3,但对于4级风速以上CCN平均浓度为4000cm-3左右;在过饱和度0.1%～0.4%间CCN浓度变化较大,过饱和度每增加0.1%,CCN浓度增加值平均约为过饱和度0.4%～1.0%间浓度增量的5倍。低过饱和度(0.1%、0.2%)下,活化率受风速影响明显,1级风速下的CCN活化率约为4级风速下的3倍,但在过饱和度1%时活化率则相差不大。CCN浓度的日变化呈双峰型,峰值时刻为北京时间08:00和18:00左右,活化率的日变化则呈双谷型,这主要是受局地排放影响的结果。利用指数函数拟合各风速下CCN浓度过饱和度谱,表明该地谱型为典型的大陆型。