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121.
James W. Beletic Sean Adkins Barry Burke Robert Reich Bernie Kosicki Vyshnavi Suntharalingham Charlie Bleau Ray DuVarney Richard Stover Jerry Nelson Francois Rigaut 《Experimental Astronomy》2005,19(1-3):103-109
All of the extremely large telescopes (ELTs) will utilize sodium laser guide star (LGS) adaptive optics (AO) systems. Most of these telescopes plan to use the Shack-Hartmann approach for wavefront sensing. In these AO systems, the laser spots in subapertures at the edge of the pupil will suffer from spot elongation due to the 10 km extent of the sodium layer and the large separation from the projection laser. This spot elongation will severely degrade the performance of standard geometry wavefront sensing systems. In this paper, we present a CCD with custom pixel morphology that aligns the pixels of each subaperture with the radial extension of the LGS spot. This CCD design will give better performance than a standard geometry CCDs for continuous wave lasers. In addition, this CCD design is optimal for a pulsed sodium laser. The pixel geometry enables each subaperture to follow a laser pulse traversing the sodium layer, providing optimal sampling of a limited number of detected photons. In addition to novel pixel layout, this CCD will also incorporate experimental JFET sense amplifiers and use CMOS design approaches to simplify the routing of biases, clocks and video output. This CCD will attain photon-noise limited performance at high frame rates, and is being incorporated in the plans for the Thirty Meter Telescope (TMT). 相似文献
122.
S. G. Kleinmann M. G. Lysaght W. L. Pughe S. E. Schneider M. F. Skrutskie M. D. Weinberg S. D. Price K. Y. Matthews B. T. Soifer J. P. Huchra C. A. Beichman T. J. Chester T. Jarrett G. L. Kopan C. J. Lonsdale J. Elias J. W. Liebert P. Seitzer 《Experimental Astronomy》1994,3(1-4):65-72
This paper describes the design, expectations, and prototyping of a new allsky survey, called 2MASS (Two Micron All Sky Survey) to be carried out with the new generation of infrared array detectors. 相似文献
123.
本文研究了在1993年3月28日之前发现的899颗超新星(SNe)的样本.其中277颗SNe被用来研究超新星在其母星系中的径向分布.我们研究了四个星系样本中超新星在产生单个超新星(称为一般超新星)的星系及在产生多个超新星(称为多重超新星)的星系中的径向分布.这四个星系样本为:总旋涡星系样本,Sb~SbC星系样本,SC星系样本,Sc~Sd星系样本.研究的结果表明:一多重超新星比一般超新星在其母星系中具有更集中于星系核心(大多数恒星形成发生的地方)的倾向,说明星系中心的恒星形成活动会影响多重超新星事件的发生从而影响超新星的频率分布 相似文献
124.
本文用微扰的方法求解在广义相对论框架下,均匀慢旋转的轴对称的稳定星体的结构方程,对旋转的处理精确到角速度的二级近似.并用10种可能的中子星的物态方程,计算了相应的稳定星体的结构.通过对物态方程G的详细计算结果,具体讨论了旋转对中子星的结构参量及各种性质的影响. 相似文献
125.
The observeduvby and Hα indices of member stars of the Hyades and Praesepe clusters have been analysed in detail for rotation effects. The Alpha
Persei, Pleiades and the Centaurus subgroup of the Scorpio—Centaurus association have been reanalysed using the observed indices
instead of the extinction-corrected indices used earlier. The observed rotation effects from the analysis of these cluster
data are found to be in excellent agreement with the theoretical predictions of Collins & Sonneborn (1977). We have also analysed
the α,c and (u − b) values of the member stars of NGC 1976, 2264, 2287, 2422, 4755,1C 2391, IC 2602 and IC 4665 for rotation effects. The results
are found to be consistent with the theoretical predictions.
The observed slopes of the rotation effects were used to determine the zero rotation main sequence values of the intermediate
band photometric indices for selected clusters. We also corrected the observed indices for each star in each cluster using
the theoretical predictions of Collins and Sonneborn and derived the ZRMS values for each cluster. The agreement between the
two determinations is found to be good. The various ZRMS curves were utilised to derive the ZRZAMS values. A preliminary calibration
of the absolute visual magnitudes as a function of α valid for ZRZAMS has also been derived. The ZRMS values of the intermediate
band photometric indices for different clusters and the ZRZAMS values are listed as a function of α.
on leave from Assumption College, Changanacherry, Kerala. 相似文献
126.
R. Capuzzo-Dolcetta A. Vicari 《Monthly notices of the Royal Astronomical Society》2005,356(3):899-912
The present work extends and deepens previous examinations of the evolution of globular cluster orbits in elliptical galaxies, by means of numerical integrations of a wide set of orbits in five self-consistent triaxial galactic models characterized by a central core and different axial ratios. These models are valid and complete in the representation of regular orbits in elliptical galaxies. Dynamical friction is definitely shown to be an efficient cause of evolution for the globular cluster systems in elliptical galaxies of any mass or axial ratio. Moreover, our statistically significant sample of computed orbits confirms that the globular cluster orbital decay times are, at least for clusters moving on box orbits, much shorter than the age of the galaxies. Consequently, the mass carried into the innermost galactic region in the form of decayed globular clusters may have contributed significantly to feeding and accreting a compact object therein. 相似文献
127.
Analysis of the available observational data for the α-Persei cluster members shows that rotation effects on the intermediate-band
indices c1 and (u-b) are considerable. In c1, rotation produces a reddening of 0.040 magnitudes per 100 km s-1 In (u-b) the effect for B stars is found to be 0.06 magnitudes per 100 km s-1 ofV sin i.
The binaries and peculiar stars are found to behave differently in the colour excess (due to rotation) versusV sin i diagrams. These empirical effects can be utilised to recalibrate these colour indices and also to separate members
that are either chemically peculiar or in binary systems. 相似文献
128.
An accurate numerical survey of the density profiles corresponding to the crusts of neutron stars for representative equation
of state models is presented. This will find application in calculations of thermal and magnetic evolution of neutron stars. 相似文献
129.
本文利用红外天文卫星点源表及哈勃望远镜导星星表对1990年新发表的75个S星进行了IRAS红外源及GSC光学对应体的证认,给出41个S星有IRAS对应体,12个S星有GSC光学对应体。 相似文献
130.
Andrés E. Piatti Ata Sarajedini Doug Geisler Juan Seguel David Clark 《Monthly notices of the Royal Astronomical Society》2005,358(4):1215-1230
Colour–magnitude diagrams (CMDs) are presented for the first time for 10 star clusters projected on to the Small Magellanic Cloud (SMC). The photometry was carried out in the Washington system C and T 1 filters allowing the determination of ages by means of the magnitude difference between the red giant clump and the main-sequence turnoff (MSTO), and metallicities from the red giant branch (RGB) locus. The clusters all have ages in the range 1.5–4 Gyr and metallicities between −1.3 < [Fe/H] < −0.6 , with respective errors of ∼0.5 Gyr and 0.3 dex. This increases substantially the sample of intermediate-age clusters in the SMC with well-derived parameters. We combine our results with those for other clusters in the literature to derive as large and homogeneous a data base as possible (totalling 26 clusters) in order to study global effects. We find evidence for two peaks in the age distribution of SMC clusters, at ∼6.5 and 2.5 Gyr, in good agreement with previous hints involving smaller samples. The most recent peak occurs at a time that corresponds to a very close encounter between the Large Magellanic Cloud (LMC) and the SMC according to the recent dynamical models of Bekki et al. that they used to explain the enhancement of LMC clusters with this age. It appears cluster formation may have been similarly stimulated in the SMC by this encounter as well. We also find very good agreement between cluster ages and metallicities and the prediction from a bursting model from Pagel and Tautvaišienė with a burst that occurred 3 Gyr ago. These two lines of evidence together favour a bursting cluster formation history as opposed to a continuous one for the SMC. 相似文献