共查询到20条相似文献,搜索用时 15 毫秒
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Hideyoshi Arakida 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
We investigated the influence of dark matter on light propagation in the solar system. We assumed the spherical symmetry of spacetime and derived the approximate solution of the Einstein equation, which consists of the gravitational attractions caused by the central celestial body, i.e. the Sun, and the dark matter surrounding it. We expressed the dark matter density in the solar system in the following simple power-law form, ?(t,r)=ρ(t)(?/r)k, where t is the coordinate time; r, the radius from the central body; ?, the normalizing factor; k, the exponent characterizing r -dependence of dark matter density; and ρ(t), the arbitrary function of time t. On the basis of the derived approximate solution, we focused on light propagation and obtained the additional corrections of the gravitational time delay and the relative frequency shift caused by the dark matter. As an application of our results, we considered the secular increase in the astronomical unit reported by Krasinsky and Brumberg (2004) and found that it was difficult to provide an explanation for the observed dAU/dt = 15 ± 4 m/century. 相似文献
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M.K. Sharma Monika Sharma U.P. Verma Suresh Chandra 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Though H2CO, H2CS, H2CCC, H2CCCC, H2CCO have been identified in cool interstellar molecular clouds, identification of H2CC is still awaited. To analyze its spectrum, collisional rate coefficients are required. We have calculated collisional rate coefficients for rotational transitions between 23 levels of ortho and para H2CC for kinetic temperatures 10, 20, 30, 40, and 50 K. The scattering problem is analyzed using the computer code MOLSCAT where the colliding partner is He atom. The interaction between H2CC and He has been calculated with GAUSSIAN 2003. For the interaction potential obtained with GAUSSIAN 2003, MOLSCAT is used to derive the parameters q(L,M,M′|E) as a function of energy E of the colliding partner. After averaging the parameters q(L,M,M′|E) over a Maxwellian distribution, the parameters Q(L,M,M′|T) as a function of the kinetic temperature T in the cloud are obtained. Finally, the collisional rate coefficients have been calculated. 相似文献
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Michihiro Takami Motohide Tamura Keigo Enya Takafumi Ootsubo Misato Fukagawa Mitsuhiko Honda Yoshiko Okamoto Shigehisa Sako Takuya Yamashita Sunao Hasegawa Hirokazu Kataza Hideo Matsuhara Takao Nakagawa Javier R. Goicoechea Kate Isaak Bruce Swinyard 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
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Huynh Anh Nguyen Le Soojong Pak Myungshin Im Minjin Kim Chae Kyung Sim Luis C. Ho 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844+349 (z = 0.064), PG 1226+023 (z = 0.158), and PG 1426+015 (z = 0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 μm), Si I (1.589 μm) and CO (6-3) (1.619 μm), and measured the velocity dispersions of PG 0844+349 to be 132 ± 110 km s−1 and PG 1426+015 to be 264 ± 215 km s−1. By using an MBH–σ relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349, log(MBH/M⊙)=7.7±5.5 and PG 1426+015,log(MBH/M⊙)=9.0±7.5. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5. 相似文献
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WenBin Shen Jinsheng Ning Dingbo Chao Jinnan Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We propose a test of the gravitational time dilation in general relativity by long term clock comparison between two stations separated in height. The geopotential difference between the two National time keeping centers in China, Lintong (A) and Beijing (B) is around 4000 geopotential unit, which corresponds to the height difference of 400 m. Two clocks CA and CB are fixed at stations A and B, respectively, which are synchronized at beginning by a portable clock C in a short time period with go-back synchronization approach. After one month, the clock C is again transported between A and B , comparing the records of the keeping time by clocks CA and CB, respectively. Calculations show that, after one month, the difference of the time durations between the clocks CA and CB is around 121 ns, if general relativity is correct. 相似文献
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P. Jakobsson D. Malesani J. Hjorth J.P.U. Fynbo B. Milvang-Jensen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
We describe the current status and recent results from our Swift/VLT legacy survey, a VLT Large Programme aimed at characterizing the host galaxies of a homogeneously selected sub-sample of Swift GRBs. The immediate goals are to determine the host luminosity function, study the effects of reddening, determine the fraction of Lyα emitters in the hosts, and obtain redshifts for targets without a reported one. The main effort so far has been the definition of a very carefully selected sample, obeying strict and well-defined criteria: 68 targets in total. Among the preliminary results is a large optical detection rate, the lack of extremely red objects (only one possible case in the sample) and an update of the Swift GRB redshift distribution with 〈z〉∼2.0. 相似文献