YNAO OpenIR中国科学院国家科学图书馆机构知识库http://ir.ynao.ac.cn:802017-11-18T02:27:47Z2017-11-18T02:27:47Z3～5μm红外天空亮度测量的多元定标模型赵志军许方宇高玲郭杰徐世春刘忠http://ir.ynao.ac.cn:80/handle/114a53/101812017-11-17T19:22:48Z2017-11-17T08:05:05Z题名: 3～5μm红外天空亮度测量的多元定标模型
作者: 赵志军; 许方宇; 高玲; 郭杰; 徐世春; 刘忠
摘要: 传统一元定标法测量红外天空亮度,面临诸多困难,如测量易受环境温度变化影响、仪器动态范围不足等。提出增加积分时间为自变量的二元定标模型,解决了仪器动态范围不足的问题;然后通过改变环境温度的系列实验,掌握了二元定标模型中仪器辐射随环境温度变化的规律;基于此,提出再增加环境温度为自变量的三元定标模型。实验数据表明,三元模型与实测数据拟合程度很高,相关系数为1.000,模型参数a、b、d,95%置信度的相对不确定度均小于0.82%,当环境保持某一温度不变时,三元模型退化为二元模型,各模型参数稳定,其相对偏差小于0.6%。最后,通过红外天空亮度实测,验证并比较了三元和二元定标模型;结果表明,三元模型定标测量法使用条件宽泛,既扩大了仪器动态范围,又不受环境温度变化影响;更重要的是,不再需要现场定标,提高了测量精度和测试效率。
摘要: The traditional univariate calibration method used in measuring infrared sky brightness is confronted with many issues, and two main issues are the insufficient dynamic response of the measuring instruments as well as the influence of the ambient temperature on the measurement result. In order to extend the dynamic response of the measuring instruments, a bivariate calibration model at the constant temperature was demonstrated in the paper, and its independent variables were radiance and exposure time. Then with the experiment data acquired in many temperatures, the variation of the bivariate calibration model in different temperature was analyzed. Thus trivariate calibration model was presented at the last part, and the goodness of the fit of the model and the experiment data was best. R -square is 1.000, and the relevant uncertainties in 95% confidence degree of a, b and d, parameters of the trivariate calibration model, were all less than 0.82%, trivariate model can be degraded to bivariate at some certain temperature, the deviation of all of parameters of degraded model were less than 0.6%; Finally, with the outfield experiment of infrared sky brightness, bivariate and trivariate calibration model were validated and compared. The benefit of this trivariate calibration model is that it can extend the dynamic response of the measuring instruments, and the precision of its measuring result is not affected by the variation of ambient temperature. Hence this model can be widely used and can achieve high-precision and highefficiency measurement without in-situ calibration.2017-11-17T08:05:05ZSynchrotron Spectrum of Fast Cooling Electrons in GRBsZhao XH(赵晓红)Bai JM(白金明)http://ir.ynao.ac.cn:80/handle/114a53/101802017-11-16T19:22:48Z2017-11-16T07:39:42Z题名: Synchrotron Spectrum of Fast Cooling Electrons in GRBs
作者: Zhao XH(赵晓红); Bai JM(白金明)
摘要: We discuss the synchrotron emission of fast cooling electrons in shocks. The fast cooling electrons behind the shocks can generate a position-dependent inhomogeneous electron distribution if they do not have enough time to mix homogeneously. This can lead to a very different synchrotron spectrum in low-frequency bands from that in the homogeneous case, due to the synchrotron absorption. In this paper, we calculate the synchrotron spectrum in the inhomogeneous case in a gamma-ray burst (GRB). Both the forward shock and the reverse shock are considered. We find that for the reverse shock dominated case, we would expect a "reverse shock bump" in the low-frequency spectrum. The spectral bump is due to the combination of synchrotron absorption in both the forward and reverse shock regions. In the low frequencies the forward shock spectrum has two unconventional segments, with spectral slopes of less than or similar to 1 and 11/8. The slope of 11/8 has been found by some authors, while the slope of less than or similar to 1 is new and due to the approximately constant electron temperature in the optically thick region. In the future, simultaneous observations in multiple bands (especially in the low-frequency bands) in the GRB early afterglow or prompt emission phases will possibly reveal these spectral characteristics and enable us to identify the reverse shock component and distinguish between the forward and reverse shock emissions. This also may be a method with which to diagnose the electron distribution status (homogeneous or inhomogeneous) after fast cooling in the relativistic shock region.2017-11-16T07:39:42ZA NON-PARAMETRIC APPROACH TO CONSTRAIN THE TRANSFER FUNCTION IN REVERBERATION MAPPINGLi, Yan-RongWang, Jian-MinBai JM(白金明)http://ir.ynao.ac.cn:80/handle/114a53/101792017-11-16T19:22:50Z2017-11-16T07:33:56Z题名: A NON-PARAMETRIC APPROACH TO CONSTRAIN THE TRANSFER FUNCTION IN REVERBERATION MAPPING
作者: Li, Yan-Rong; Wang, Jian-Min; Bai JM(白金明)
摘要: Broad emission lines of active galactic nuclei stem from a spatially extended region (broad-line region, BLR) that is composed of discrete clouds and photoionized by the central ionizing continuum. The temporal behaviors of these emission lines are blurred echoes of continuum variations (i.e., reverberation mapping, RM) and directly reflect the structures and kinematic information of BLRs through the so-called transfer function (also known as the velocity-delay map). Based on the previous works of Rybicki and Press and Zu et al., we develop an extended, non-parametric approach to determine the transfer function for RM data, in which the transfer function is expressed as a sum of a family of relatively displaced Gaussian response functions. Therefore, arbitrary shapes of transfer functions associated with complicated BLR geometry can be seamlessly included, enabling us to relax the presumption of a specified transfer function frequently adopted in previous studies and to let it be determined by observation data. We formulate our approach in a previously well-established framework that incorporates the statistical modeling of continuum variations as a damped random walk process and takes into account long-term secular variations which are irrelevant to RM signals. The application to RM data shows the fidelity of our approach.2017-11-16T07:33:56ZCyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMaHan, Z. -TQian SB(钱声帮)Irina, VoloshinaZhu, L. -Yhttp://ir.ynao.ac.cn:80/handle/114a53/101782017-11-16T19:22:50Z2017-11-16T07:06:04Z题名: Cyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMa
作者: Han, Z. -T; Qian SB(钱声帮); Irina, Voloshina; Zhu, L. -Y
摘要: DV UMa is an eclipsing dwarf nova with an orbital period of similar to 2.06 hr, which lies just at the bottom edge of the period gap. To detect its orbital period changes, we present 12 new mid-eclipse times by using our CCD photometric data and archival data. The latest version of the O-C diagram, combined with the published mid-eclipse times in quiescence, and spanning similar to 30 years, was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of 17.58(+/- 0.52) years and an amplitude of 71.1(+/- 6.7) s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object, because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as M-3 sin i' = 0.025(+/- 0.004) M.. If the third body is in the orbital plane (i.e., i' = i = 82 degrees.9) of the eclipsing pair, this would indicate it is a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of similar to 8.6 au in an eccentric orbit (e. = 0.44).2017-11-16T07:06:04ZNUMERICAL INTEGRAL OF RESISTANCE COEFFICIENTS IN DIFFUSIONZhang QS(张钱生)http://ir.ynao.ac.cn:80/handle/114a53/101772017-11-16T19:22:51Z2017-11-16T06:59:11Z题名: NUMERICAL INTEGRAL OF RESISTANCE COEFFICIENTS IN DIFFUSION
作者: Zhang QS(张钱生)
摘要: The resistance coefficients in the screened Coulomb potential of stellar plasma are evaluated to high accuracy. I have analyzed the possible singularities in the integral of scattering angle. There are possible singularities in the case of an attractive potential. This may result in a problem for the numerical integral. In order to avoid the problem, I have used a proper scheme, e.g., splitting into many subintervals where the width of each subinterval is determined by the variation of the integrand, to calculate the scattering angle. The collision integrals are calculated by using Romberg's method, therefore the accuracy is high (i.e., similar to 10(-12)). The results of collision integrals and their derivatives for -7 <= psi <= 5 are listed. By using Hermite polynomial interpolation from those data, the collision integrals can be obtained with an accuracy of 10(-10). For very weakly coupled plasma (psi >= 4.5), analytical fittings for collision integrals are available with an accuracy of 10(-11). I have compared the final results of resistance coefficients with other works and found that, for a repulsive potential, the results are basically the same as others'; for an attractive potential, the results in cases of intermediate and strong coupling show significant differences. The resulting resistance coefficients are tested in the solar model. Comparing with the widely used models of Cox et al. and Thoul et al., the resistance coefficients in the screened Coulomb potential lead to a slightly weaker effect in the solar model, which is contrary to the expectation of attempts to solve the solar abundance problem.2017-11-16T06:59:11ZTHE SHAPE OF SOLAR CYCLES DESCRIBED BY A SIMPLIFIED BINARY MIXTURE OF GAUSSIAN FUNCTIONSLi FY(李富羽)Xiang, N. B.Kong, D. F.Xie, J. L.http://ir.ynao.ac.cn:80/handle/114a53/101762017-11-09T19:22:50Z2017-11-09T03:19:10Z题名: THE SHAPE OF SOLAR CYCLES DESCRIBED BY A SIMPLIFIED BINARY MIXTURE OF GAUSSIAN FUNCTIONS
作者: Li FY(李富羽); Xiang, N. B.; Kong, D. F.; Xie, J. L.
摘要: Sunspot cycles usually present a double-peak structure. This work is devoted to using a function to describe the shape of sunspot cycles, including bimodal cycles, and we find that the shape of sunspot cycles can be described by a binary mixture of Gaussian functions with six parameters, two amplitudes, two gradients of curve, and two rising times, and the parameters could be reduced to three. The fitting result of this binary mixture of Gaussian functions is compared with some other functions used previously in the literature, and this function works pretty well, especially at cycle peaks. It is worth mentioning that the function can describe well the shape of those sunspot cycles that show double peaks, and it is superior to the binary mixture of the Laplace functions that was once utilized. The Solar Influences Data Analysis Center, on behalf of the World Data Center, recently issued a new version (version 2) of sunspot number. The characteristics of sunspot cycles are investigated, based on the function description of the new version.2017-11-09T03:19:10ZA New Photometric Study of Ap and Am Stars in the InfraredChen PS(陈培生)Liu, J. Y.Shan, H. G.http://ir.ynao.ac.cn:80/handle/114a53/101752017-11-09T19:22:51Z2017-11-09T03:05:54Z题名: A New Photometric Study of Ap and Am Stars in the Infrared
作者: Chen PS(陈培生); Liu, J. Y.; Shan, H. G.
摘要: In this paper, 426 well known confirmed Ap and Am stars are photometrically studied in the infrared. The 2MASS, Wide-field Infrared Survey Explorer (WISE), and IRAS data are employed to make analyses. The results in this paper have shown that in the 1-3 mu m region over 90% Ap and Am stars have no or little infrared excesses, and infrared radiations in the near-infrared from these stars are probably dominated by the free-free emissions. It is also shown that in the 3-12 mu m region, the majority of Ap stars and Am stars have very similar behavior, i.e., in the W1-W2 (3.4-4.6 mu m) region, over half of Ap and Am stars have clear infrared excesses, which are possibly due to the binarity, the multiplicity, and/or the debris disk, but in the W2-W3 (4.6-12 mu m) region they have no or little infrared excess. In addition, in the 12-22 mu m region, some of Ap stars and Am stars show the infrared excesses and infrared radiations for these Ap and Am stars are probably due to the free-free emissions. In addition, it is seen that the probability of being the binarity, the multiplicity and/or the debris disk for Am stars is much higher than that for Ap stars. Furthermore, it can be seen that, in general, no relations can be found between infrared colors and spectral types either for Ap stars or for Am stars.2017-11-09T03:05:54ZLONG-TERM TREND OF SUNSPOT NUMBERSGao PX(高朋鑫)http://ir.ynao.ac.cn:80/handle/114a53/101742017-11-06T19:22:48Z2017-11-06T08:40:06Z题名: LONG-TERM TREND OF SUNSPOT NUMBERS
作者: Gao PX(高朋鑫)
摘要: Using the Hilbert-Huang Transform method, we investigate the long-term trend of yearly mean total sunspot numbers in the time interval of 1700-2015, which come from the World Data Center-the. sunspot Index and long-term solar observations. The main findings of this study are summarized below. (1) From the adaptive trend, which is extracted from the yearly mean total sunspot numbers, we can find that the value gradually increases during the time period 1700-1975, then decreases gradually from 1975 to 2015. (2) The Centennial Gleissberg Cycle is extracted from the yearly mean total sunspot numbers and confirms that. a new grand minimum is in progress; the Dalton Minimum, the Gleissberg Minimum, and low level of solar activity during solar cycle 24 (the part of the new grand minimum) all can be understood as minima of the Centennial Gleissberg Cycle. (3) Based on the adaptive (overall) trend, and the 100-year and longer timescale trend of yearly mean total sunspot numbers, we can infer that the level of solar activity during the new grand minimum may be close to that during the Gleissberg Minimum, slightly higher than that during the. Dalton Minimum, and significantly higher than that during the. Maunder Minimum. Our results do not support the suggestion. that a new grand minimum, somewhat resembling the Maunder Minimum, is in progress.2017-11-06T08:40:06ZVertical Structure of Radiation-pressure-dominated Thin Disks: Link between Vertical Advection and Convective StabilityGong, Hong-YuGu, Wei-Minhttp://ir.ynao.ac.cn:80/handle/114a53/101732017-11-06T19:22:49Z2017-11-06T08:24:48Z题名: Vertical Structure of Radiation-pressure-dominated Thin Disks: Link between Vertical Advection and Convective Stability
作者: Gong, Hong-Yu; Gu, Wei-Min
摘要: In the classic picture of standard thin accretion disks, viscous heating is balanced by radiative cooling through the diffusion process, and the radiation-pressure-dominated inner disk suffers convective instability. However, recent simulations have shown that, owing to the magnetic buoyancy, the vertical advection process can significantly contribute to energy transport. In addition, in comparing the simulation results with the local convective stability criterion, no convective instability has been found. In this work, following on from simulations, we revisit the vertical structure of radiation-pressure-dominated thin disks and include the vertical advection process. Our study indicates a link between the additional energy transport and the convectively stable property. Thus, the vertical advection not only significantly contributes to the energy transport, but it also plays an important role in making the disk convectively stable. Our analyses may help to explain the discrepancy between classic theory and simulations on standard thin disks.2017-11-06T08:24:48Z天文科技领域云:大数据时代的天文教育和科研信息化平台肖健于策崔辰州李长华何勃亮樊东卫刘梁陈肖张海龙王传军http://ir.ynao.ac.cn:80/handle/114a53/101722017-10-30T02:59:37Z2017-10-23T07:59:27Z题名: 天文科技领域云:大数据时代的天文教育和科研信息化平台
作者: 肖健; 于策; 崔辰州; 李长华; 何勃亮; 樊东卫; 刘梁; 陈肖; 张海龙; 王传军
摘要: 天文科技领域云以中国天文数据中心的数据资源为基础,旨在为天文望远镜的观测时间申请、数据归档、检索、分析以及科研课题提供服务。通过利用云计算和虚拟化技术,系统集成了国内主要天文台站的存储、数据、计算、软件等资源,形成了一个物理上分散、逻辑上统一的网络化科学研究平台。天文科技领域云既为现代观测天文学研究提供了全生命周期的支持,又为数据驱动的天文教育和科普提供了开放平台。
摘要: AstroCloud is based on the data resources of the China Astronomical Data Center．It aims to provide services for the observation time application for the astronomical telescope,data archiving,data retrieval,data analysis ands cientific research projects．Through the use of cloud computing and virtualization technology,the system integrates the storage,data,calculation,software and other resources of the main observatories in China,and forms a network platform of scientific research which is physically dispersed and logically unified．AstroCloud provides both the whole life cycle of modern observational astronomical research and the open platform for the data-driven astronomical education and popularization of science．2017-10-23T07:59:27Z