Magnetic deformation of magnetars for the giant flares of the soft gamma-ray repeaters

We present one possible mechanism for the giant flares of the soft gamma-ray repeaters (SGRs) within the framework of the magnetar (superstrongly magnetized neutron star) model, motivated by the positive period increase associated with the August 27 event from SGR 1900+14. From second-order perturbation analysis of the equilibrium of the magnetic polytrope, we find that there exist different equilibrium states separated by the energy of the giant flares and the shift in the moment of inertia to cause the period increase. This suggests that, if we assume that global reconfiguration of the internal magnetic field of     suddenly occurs, the positive period increase     as well as the energy ≳10⁴⁴ erg of the giant flares may be explained. The moment of inertia can increase with a release of energy, because the star shape deformed by the magnetic field can be prolate rather than oblate. In this mechanism, since oscillation of the neutron star will be excited, a ∼ ms-period pulsation of the burst profile and an emission of gravitational waves are expected. The gravitational waves could be detected by planned interferometers such as LIGO, VIRGO and LCGT.     

Non-parametric inversion of gravitational lensing systems with few images using a multi-objective genetic algorithm

Galaxies acting as gravitational lenses are surrounded by, at most, a handful of images. This apparent paucity of information forces one to make the best possible use of what information is available to invert the lens system. In this paper, we explore the use of a genetic algorithm to invert in a non-parametric way strong lensing systems containing only a small number of images. Perhaps the most important conclusion of this paper is that it is possible to infer the mass distribution of such gravitational lens systems using a non-parametric technique. We show that including information about the null space (i.e. the region where no images are found) is prerequisite to avoid the prediction of a large number of spurious images, and to reliably reconstruct the lens mass density. While the total mass of the lens is usually constrained within a few per cent, the fidelity of the reconstruction of the lens mass distribution depends on the number and position of the images. The technique employed to include null space information can be extended in a straightforward way to add additional constraints, such as weak-lensing data or time-delay information.     

阿尔金断裂西南端走向及延伸的区域重力场制约

阿尔金断裂带作为青藏高原北部边界的重要组成部分,长期以来受到国内外地学界的广泛关注与研究。笔者通过对区域重力场的分析,认为阿尔金断裂的西南端并非止于郭扎错,而是在郭扎错北东附近分为两个分支,一支经郭扎错继续向南西西延伸,过龙木错后由空喀山口进入克什米尔,另一支继续向南西延伸,经吉普以西止于班公湖附近的班公湖—怒江结合带,并且,经吉普以西止于班公湖附近的这一分支形成时间要早于经郭扎错、龙木错后由空喀山口进入克什米尔的这一分支。     

基于向量化的扰动引力矢量快速并行算法

无人飞行器在飞行过程中受地球外部扰动引力影响,对其精确控制需要计算飞行轨迹点扰动引力。为有效恢复地球外部引力场,常采用地球重力场位系数模型进行计算,但其计算耗时随模型阶数的升高而呈指数增加。本文提出一种扰动引力矢量计算的向量化方法,推导出利用地球重力场模型计算扰动引力三分量的向量化表达公式,并利用CUDA（compute unified device architecture）异构并行算法进行并行化以达到快速计算单点扰动引力的目的。通过仿真实验可知,本文所提方法可有效减少单点扰动引力计算耗时,利用跨阶次递推法进行单点计算加速比可达8以上,最高可达13.20;利用Belikov递推法进行单点计算加速比可达6以上,最高可达8.99。     

Gravitational waves from compact objects

Large ground-based laser beam interferometers are presently in operation both in the USA(LIGO) and in Europe(VIRGO) and potential sources that might be detected by these instruments are revisited.The present generation of detectors does not have a sensitivity high enough to probe a significant volume of the universe and,consequently,predicted event rates are very low.The planned advanced generation of interferometers will probably be able to detect,for the first time,a gravitational signal.Advanced LIGO and...     

Realisation of a fully‐deterministic microlensing observing strategy for inferring planet populations

Within less than 15 years, the count of known planets orbiting stars other than the Sun has risen from none to more than 400 with detections arising from four successfully applied techniques: Doppler‐wobbles, planetary transits, gravitational microlensing, and direct imaging. While the hunt for twin Earths is on, a statistically well‐defined sample of the population of planets in all their variety is required for probing models of planet formation and orbital evolution so that the origin of planets that harbour life, like and including ours, can be understood. Given the different characteristics of the detection techniques, a complete picture can only arise from a combination of their respective results. Microlensing observations are well‐suited to reveal statistical properties of the population of planets orbiting stars in either the Galactic disk or bulge from microlensing observations, but a mandatory requirement is the adoption of strictly‐deterministic criteria for selecting targets and identifying signals. Here, we describe a fully‐deterministic strategy realised by means of the ARTEMiS (Automated Robotic Terrestrial Exoplanet Microlensing Search) system at the Danish 1.54‐m telescope at ESO La Silla between June and August 2008 as part of the MiNDSTEp (Microlensing Network for the Detection of Small Terrestrial Exoplanets) campaign, making use of immediate feedback on suspected anomalies recognized by the SIGNALMEN anomaly detector. We demonstrate for the first time the feasibility of such an approach, and thereby the readiness for studying planet populations down to Earth mass and even below, with ground‐based observations. While the quality of the real‐time photometry is a crucial factor on the efficiency of the campaign, an impairment of the target selection by data of bad quality can be successfully avoided. With a smaller slew time, smaller dead time, and higher through‐put, modern robotic telescopes could significantly outperform the 1.54‐m Danish, whereas lucky‐imaging cameras could set new standards for high‐precision follow‐up monitoring of microlensing events (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

空中重力异常代表误差在空域和频域的比较分析

在空域,利用严密的向上延拓公式将地面重力数据上延至空中不同高度,而后与相应的地面重力数据比较从而得到不同高度的代表误差.在频域,构建了新的代表误差模型,计算了不同高度、不同分辨率下的代表误差.实际算例表明,在空域,对于地形平坦区域,在1 km高度以下,5'空中重力数据直接代表地面重力数据的误差小于1×10-5 m/s2...     

ASTROD-GW时间迟延干涉

ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical Devices] optimized for Gravitation Wave detection)是ASTROD专注于引力波探测的优化方案,组成任务的3个航天器分别位于日地拉格朗日点L3、L4和L5点附近,组成臂长为2.6× 108 km的干涉阵列.根据优化得到的ASTROD-GW 20 yr任务轨道,利用CGC2.7 (CGC:Center for Gravitation and Cosmology)星历,采用适当数值计算的方法,对引力波探测中所用到的时间迟延干涉路径进行分析和计算.     

利用弱引力透镜效应的尖峰和尺度-尺度相关统计区分暗能量模型

为了研究不同宇宙学模型下弱引力透镜效应的性质,利用N-体模拟产生的数据,通过光线追踪技术,生成二维的κ样本.对应于不同的暗能量状态方程参数的模型,即w=-0.8,w=-1.0,w=-1.2,生成了3组样本.对于这些模型所生成的样本视场均为3°×3°,并假设所有作为背景源的星系都分布在z=1处的平面上.对这些κ场的样本均进行了尖峰统计和尺度-尺度相关的统计.对尖峰的统计结果显示,包含噪声的κ场中尖峰分布在不同模型下的差别还是存在的.噪声改变了中等幅值和小幅值的尖峰分布,而对高幅值的尖峰分布影响不大.同时降噪后κ场中高幅值尖峰分布的结果表明,降噪后不同模型间高幅值尖峰分布的差别还是非常明显的.对于尺度-尺度相关统计,分析了不同模型的尺度-尺度相关系数的累积概率分布函数,w=-1.2的模型与w=-0.8和w=-1.0的模型的差别能达到20%和30%.因此尺度-尺度相关的统计结合尖峰数目的统计,可以做为确定暗能量状态参数的一种新的手段.