Limits on the 2.2-μm contrast ratio of the close-orbiting planet HD 189733b

We obtained 238 spectra of the close-orbiting extrasolar giant planet HD 189733b with resolution   R ∼ 15 000  during one night of observations with the Near-Infrared High-Resolution Spectrograph (NIRSPEC), at the Keck II Telescope. We have searched for planetary absorption signatures in the  2.0–2.4 μm  region where H₂O and CO are expected to be the dominant atmospheric opacities. We employ a phase-dependent orbital model and tomographic techniques to search for the planetary absorption signatures in the combined stellar and planetary spectra. Because potential absorption signatures are hidden in the noise of each single exposure, we use a model list of lines to apply a spectral deconvolution. The resulting mean profile possesses a signal-to-noise ratio (S/N) that is 20 times greater than that found in individual lines. Our spectral time series thus yields spectral signatures with a mean S/N = 2720. We are unable to detect a planetary signature at a contrast ratio of  log₁₀( F _p/ F _*) =−3.40  , with 63.8 per cent confidence. Our findings are not consistent with model predictions which nevertheless give a good fit to mid-infrared observations of HD 189733b. The 1σ result is a factor of 1.7 times less than the predicted 2.185-μm planet/star flux ratio of  log₁₀( F _p/ F _*) ∼−3.16  .     

TPS测设道路填挖边线方法探讨

道路建设中,测设填挖线是经常遇到的问题,就此提出了TPS(全站仪)在任意控制点设站、测定辅助点和填挖点的放样方法。该方法的关键之处是,利用曲线要素推算各放样点的坐标,然后在道路施工现场附近选择一视野开阔的控制点安置TPS,一次性放样出全视野内的辅助点和填挖点,并连接填挖点组成填挖边线。为保证各阶削坡的精度,应注意保护各辅助点的平面位置,正确地削出最上阶平台,以控制以下各阶削坡。而以往的放样方法是抬竿法,需要在逐个横断面多次设站,用定向、量距、抬高的方法放样填挖点。这种方法的缺点是:效率低下,作业难度大,累计误差大。显然,用TPS一次设站,放样若干横断面填挖点的方法,提高了施工效率,降低了作业难度,且提高了放样点的精度。     

Extragalactic Astronomy with the VLTI: a new window on the Universe

Interferometry in the optical and near infrared has so far played a marginal role in Extragalactic Astronomy. Active Galactic Nuclei are the brightest and most compact extragalactic sources, nonetheless only a very limited number could be studied with speckle interferometry and none with long baseline interferometry. The VLTI will allow the study of moderately faint extragalactic objects with very high spatial resolution thus opening a new window on the universe. With this paper we focus on three scientific cases to show how AMBER and MIDI can be used to tackle open issues in extragalactic astronomy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Palaeoecological evidence of changes in vegetation and climate during the Holocene in the pre‐Polar Urals,northeast European Russia

This study investigated Holocene tree‐line history and climatic change in the pre‐Polar Urals, northeast European Russia. A sediment core from Mezhgornoe Lake situated at the present‐day alpine tree‐line was studied for pollen, plant macrofossils, Cladocera and diatoms. A peat section from Vangyr Mire in the nearby mixed mountain taiga zone was analysed for pollen. The results suggest that the study area experienced a climatic optimum in the early Holocene and that summer temperatures were at least 2°C warmer than today. Tree birch immigrated to the Mezhgornoe Lake area at the onset of the Holocene. Mixed spruce forests followed at ca. 9500–9000 ¹⁴C yr BP. Climate was moist and the water level of Mezhgornoe Lake rose rapidly. The hypsithermal phase lasted until ca. 5500–4500 ¹⁴C yr BP, after which the mixed forest withdrew from the Mezhgornoe catchment as a result of the climate cooling. The gradual altitudinal downward shift of vegetation zones resulted in the present situation, with larch forming the tree‐line. Copyright © 2003 John Wiley & Sons, Ltd.     

Analytical solutions for saturated P cygni type profiles II: General case

As in the first part of the present study (Sapar et al., 2002) we use the β-law for velocity of stellar wind and the Sobolev approximation for radiative transfer. Here we have succeeded to derive general and relatively simple analytical formulae in elementary functions for saturated P Cygni type line profiles if parameter 2β is arbitrary positive integer (in the first part we studied the cases 2β ≤ 4). The four terms obtained describe contributions to the line profile due to isotropic and anisotropic parts of optical thickness in the source function of the light-scattering layer followed by isotropic and anisotropic parts of multiple scattering. The limits of acceptability of the Sobolev approximation for β-law have been discussed and specified. This revised version was published online in July 2006 with corrections to the Cover Date.     

矩谱法求磁性体质心的若干问题

B K Bhattachryya(1975)推导的求磁性体质心的矩谱公式理论严谨,计算速度快,并且有不需要预先知道磁性体磁化率的特点。在该公式的基础上,本文对求质心的各种影响因素作了细致讨论,推导出了提高求解质心精度的改正公式。