共查询到20条相似文献，搜索用时 377 毫秒
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F. Rossi C. Guidorzi L. Amati F. Frontera P. Romano S. Campana G. Chincarini E. Montanari A. Moretti G. Tagliaferri 《Monthly notices of the Royal Astronomical Society》2008,388(3):1284-1292
Using a sample of 14 BeppoSAX and 74 Swift GRBs with measured redshift we tested the correlation between the intrinsic peak energy of the time-integrated spectrum, E p, i , the isotropic-equivalent peak luminosity, L p,iso , and the duration of the most intense parts of the GRB computed as T 0.45 ('Firmani correlation'). For 41 out of 88 GRBs we could estimate all of the three required properties. Apart from 980425, which appears to be a definite outlier and notoriously peculiar in many respects, we used 40 GRBs to fit the correlation with the maximum likelihood method discussed by D'Agostini, suitable to account for the extrinsic scatter in addition to the intrinsic uncertainties affecting every single GRB. We confirm the correlation. However, unlike the results by Firmani et al., we found that the correlation does have a logarithmic scatter comparable with that of the E p, i – E iso ('Amati') correlation. We also find that the slope of the product L p,iso T 0.45 is equal to ∼0.5, which is consistent with the hypothesis that the E p, i – L p,iso – T 0.45 correlation is equivalent to the E p, i – E iso correlation (slope ∼0.5). We conclude that, based on presently available data, there is no clear evidence that the E p, i – L p,iso – T 0.45 correlation is different (both in terms of slope and dispersion) from the E p, i – E iso correlation. 相似文献
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In this article we describe a case study of how NOAO is considering improving its management of Target‐of‐Opportunity (ToO) observations by integrating VOEvent into the flow of activities. We believe that using VOEvent to help document and track the use of ToO time will improve the user experience of ToOs at NOAO. It will also greatly aid in the management of the process and of the resulting data, allowing us to better track the ownership and provenance of the data and any resulting data products. Finally, it will provide an important method of archival access to the data and data “collections,” which might include not only processed data from a single VOEvent triggered observation but could also include multiple observations traceable to a single (or set of related) VOEvents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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J. D. McEwen M. P. Hobson A. N. Lasenby D. J. Mortlock 《Monthly notices of the Royal Astronomical Society》2006,369(4):1858-1868
Many of the current anomalies reported in the WMAP text ( WMAP ) one-year data disappear after 'correcting' for the best-fitting embedded Bianchi type VII h component, albeit assuming no dark energy component. We investigate the effect of this Bianchi correction on the detections of non-Gaussianity in the WMAP data that we previously made using directional spherical wavelets. We confirm that the deviations from Gaussianity in the kurtosis of spherical Mexican hat wavelet coefficients are eliminated once the data are corrected for the Bianchi component, as previously discovered by Jaffe et al. This is due to the reduction of the cold spot at Galactic coordinates ( l , b ) = (209°, −57°) , which Cruz et al. claimed to be the sole source of non-Gaussianity introduced in the kurtosis. Our previous detections of non-Gaussianity observed in the skewness of spherical wavelet coefficients are not reduced by the Bianchi correction. Indeed, the most significant detection of non-Gaussianity made with the spherical real Morlet wavelet at a significant level of 98.4 per cent remains (using a very conservative method to estimate the significance). Furthermore, we perform preliminary tests to determine if foregrounds or systematics are the source of this non-Gaussian signal, concluding that it is unlikely that these factors are responsible. We make our code to simulate Bianchi-induced temperature fluctuations publicly available. 相似文献
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J. Fleming A. Hibbert K. L. Bell & N. Vaeck 《Monthly notices of the Royal Astronomical Society》1998,300(3):767-772
The superposition of configurations (SOC) method has been used to calculate f -values for the Mg ii doublet at 1240 Å, which has been observed in the interstellar medium near stars such as ζ Ophiuchi. Our best value for the multiplet oscillator strength is 0.00083. SOC calculations have also been undertaken for the stronger (3s−3p) doublet at 2800 Å giving a multiplet f -value of 0.92. 相似文献
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Flavio De Lorenzi Victor P. Debattista † Ortwin Gerhard Niranjan Sambhus 《Monthly notices of the Royal Astronomical Society》2007,376(1):71-88
We describe a made-to-measure (M2M) algorithm for constructing N -particle models of stellar systems from observational data (χ2 M2M), extending earlier ideas by Syer & Tremaine. The algorithm properly accounts for observational errors, is flexible, and can be applied to various systems and geometries. We implement this algorithm in a parallel code nmagic and carry out a sequence of tests to illustrate its power and performance. (i) We reconstruct an isotropic Hernquist model from density moments and projected kinematics and recover the correct differential energy distribution and intrinsic kinematics. (ii) We build a self-consistent oblate three-integral maximum rotator model and compare how the distribution function is recovered from integral field and slit kinematic data. (iii) We create a non-rotating and a figure rotating triaxial stellar particle model, reproduce the projected kinematics of the figure rotating system by a non-rotating system of the same intrinsic shape, and illustrate the signature of pattern rotation in this model. From these tests, we comment on the dependence of the results from χ2 M2M on the initial model, the geometry, and the amount of available data. 相似文献
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P. Cabella M. Liguori F. K. Hansen D. Marinucci S. Matarrese L. Moscardini N. Vittorio 《Monthly notices of the Royal Astronomical Society》2005,358(2):684-692
We test the consistency of estimates of the non-linear coupling constant f NL using non-Gaussian cosmic microwave background (CMB) maps generated by the method described in the work of Liguori, Matarrese & Moscardini. This procedure to obtain non-Gaussian maps differs significantly from the method used in previous works on the estimation of f NL . Nevertheless, using spherical wavelets, we find results in very good agreement with Mukherjee & Wang, showing that the two ways of generating primordial non-Gaussian maps give equivalent results. Moreover, we introduce a new method for estimating the non-linear coupling constant from CMB observations by using the local curvature of the temperature fluctuation field. We present both Bayesian credible regions (assuming a flat prior) and proper (frequentist) confidence intervals on f NL , and discuss the relation between the two approaches. The Bayesian approach tends to yield lower error bars than the frequentist approach, suggesting that a careful analysis of the different interpretations is needed. Using this method, we estimate f NL =−10+270 −260 at the 2σ level (Bayesian) and f NL =−10+310 −270 (frequentist). Moreover, we find that the wavelet and the local curvature approaches, which provide similar error bars, yield approximately uncorrelated estimates of f NL and therefore, as advocated in the work of Cabella et al., the estimates may be combined to reduce the error bars. In this way, we obtain f NL =−5 ± 85 and f NL =−5 ± 175 at the 1σ and 2σ level respectively using the frequentist approach. 相似文献
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W. I. Clarkson B. Enoch C. A. Haswell A. J. Norton D. J. Christian A. Collier Cameron S. R. Kane K. D. Horne T. A. Lister R. A. Street R. G. West D. M. Wilson N. Evans A. Fitzsimmons C. Hellier S. T. Hodgkin J. Irwin F. P. Keenan J. P. Osborne N. R. Parley D. L. Pollacco R. Ryans I. Skillen P. J. Wheatley 《Monthly notices of the Royal Astronomical Society》2007,381(2):851-864
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S. R. Kane W. I. Clarkson R. G. West D. M. Wilson D. J. Christian A. Collier Cameron B. Enoch T. A. Lister R. A. Street A. Evans A. Fitzsimmons C. A. Haswell C. Hellier S. T. Hodgkin K. Horne J. Irwin F. P. Keenan A. J. Norton J. Osborne N. R. Parley D. L. Pollacco R. Ryans I. Skillen P. J. Wheatley 《Monthly notices of the Royal Astronomical Society》2008,384(3):1097-1108
The Wide Angle Search for Planets (WASP) survey currently operates two installations, designated SuperWASP-N and SuperWASP-S, located in the Northern and Southern hemispheres, respectively. These installations are designed to provide high time-resolution photometry for the purpose of detecting transiting extrasolar planets, asteroids, and transient events. Here, we present results from a transit-hunting observing campaign using SuperWASP-N covering a right ascension (RA) range of 06h < RA < 16h . This paper represents the fifth and final in the series of transit candidates released from the 2004 observing season. In total, 729 335 stars from 33 fields were monitored with 130 566 having sufficient precision to be scanned for transit signatures. Using a robust transit detection algorithm and selection criteria, six stars were found to have events consistent with the signature of a transiting extrasolar planet based on the photometry, including the known transiting planet XO-1b. These transit candidates are presented here along with discussion of follow-up observations and the expected number of candidates in relation to the overall observing strategy. 相似文献
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The ab initio R -matrix method is used to calculate effective collision strengths for electron-impact excitation of the sulphur-like ion Cl ii in the close-coupling approximation. All 10 astrophysically important fine-structure forbidden transitions within the 3s2 3p4 , , ground configuration levels are considered. The 12 lowest LS target states are included in the calculation. Effective collision strengths are obtained by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. Results are presented for electron temperatures in the range log T (K)=3.3 to log T (K)=5.5 , appropriate for astrophysical applications. These are the only effective collision strength data that are currently available. 相似文献
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We show how the excursion set moving barrier model for halo abundances may be generalized to the local non-Gaussian f nl model. Our estimate assumes that the distribution of step sizes depends on f nl , but that they are otherwise uncorrelated. Our analysis is consistent with previous results for the case of a constant barrier, and highlights some implicit assumptions. It also clarifies the basis of an approximate analytic solution to the moving barrier problem in the Gaussian case, and shows how it might be improved. 相似文献
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Franco Cataldo Giovanni Strazzulla Susana Iglesias-Groth 《Monthly notices of the Royal Astronomical Society》2009,394(2):615-623
The stability of C60 and C70 fullerenes in the interstellar medium deposited on dust surface or embedded in meteorites and comets has been simulated with γ irradiation and with He+ ion bombardment. It is shown by vibrational spectroscopy that a γ radiation dose of 2.6 MGy (1 Gy = 1 joule absorbed energy per kilogram) causes partial oligomerization of both C60 and C70 fullerenes. Oligomers are made by fullerene cages chemically connected each other which can yield back free fullerenes by a thermal treatment. The amount of irreversibly polymerized fullerenes caused by 2.6 MGy as deduced as the toluene insoluble fraction has been determined as 1.7 and 15 per cent by weight, respectively, for C60 and C70 fullerene. The radiation dose generated by radionuclides decay and expected to be delivered to fullerenes buried at a depth of more than 20 m in comets and meteorites is about 3 MGy per 109 yr. Since fullerenes are by far resistant to such radiation dose they can survive for at least some billion years inside comets and meteorites and in fact have been detected inside certain carbonaceous chondrites. On the other hand, the direct exposure of fullerenes to cosmic rays for instance when they are adsorbed or deposited on the surface of carbon dust corresponds to the delivery of a radiation dose comprised between 30 and 65 MGy per 109 yr. Experimental bombardment of both C60 and C70 fullerenes for instance with He+ ions has shown that the complete amorphization occurs at about 250 MGy. Thus in ∼4 Gyr exposure to cosmic rays it is expected a complete amorphization. 相似文献
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全日面矢量磁像仪(Full-disk vector MagnetoGraph, FMG)是先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)的主载荷之一,摆镜作为FMG稳像系统的重要组成部分,其力学性能是决定载荷观测指标的重要一环,需要对其进行仿真.设计了一种侧面固定的柔性支撑镜体结构,通过调整垫片厚度,可以得到由弹性压片提供的不同大小支持力.为了确定合理的支持力范围,建立3种不同参数模型,使用有限元软件对摆镜模型进行了在轨无重力环境的静力学仿真以及摆镜摆动频率为100 Hz、摆幅为±0.1 mrad时的动力学仿真,并进一步分析了地面有重力试验环境对面形的影响.仿真结果表明所设计的摆镜机构模型均满足通光口径内静态和动态的面形波峰波谷差(PeakValley, PV)小于1/10波长,面形均方根误差(Root Mean Square, RMS)小于1/40波长的光学系统要求,地面有重力环境不会对面形产生显著影响.在仿真结果的基础上,对其中一种模型进行加工装配和实际测试,测试结果表明摆镜结构设计合理,仿真计算结果有效. 相似文献