共查询到20条相似文献，搜索用时 375 毫秒
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D.R. Bates 《Planetary and Space Science》1974,22(8):1268
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N. D. Melikian V. S. Tamazian A. A. Karapetian A. L. Samsonian G. R. Kostandian 《Astrophysics》2011,54(2):203-213
A search for Hα objects in four fields with an overall area of about 0.14 square degrees in the region of NGC 6910 (the core
of the known Cyg OB9 association) has led to the discovery of 64 emission stars, of which 49 are newly detected. The high
surface density is indicative of a very rich T association or, possibly, of the projection of several T associations onto
one another in this direction. The latter possibility is also indicated by the range of the R photometric stellar magnitudes
of the emission stars, 9m.68-19m.42. A comparison with earlier observations shows that for many of the stars, the emission line intensity is variable. A P
Cyg Hα line profile is recorded for the star V 1515 Cyg with an emission component equivalent width that greatly exceeds the
equivalent absorption width. 相似文献
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D. B. Melrose 《Astrophysics and Space Science》1979,64(1):45-48
In their discussion of the transfer of polarized radiation in a weakly anisotropic, weakly inhomogeneous plasma, Cheng and Fung (1977) have included terms which describe the effects of mode coupling and of the variation of the characteristic polarizations. The latter effect is nonphysical, and only the mode-coupling term should be retained. As the problem was formulated by Cheng and Fung, the two terms would cancel exactly; consequently, when corrected, the work of Cheng and Fung leads to a simple and useful method of including the effects of mode coupling in the weak anisotropy limit.On leave from Department of Theoretical Physics, Faculty of Science, Australian National University. 相似文献
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Abstract— We discuss possible evidence for a dilution of 14C caused by the Tunguska impact event, proposed by Rasmussen et al. (1999). The results presented in that paper and other available information do not support this hypothesis. 相似文献
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Joachim Müller Sven Simon Yung-Ching Wang Uwe Motschmann Daniel Heyner Josef Schüle Wing-Huen Ip Gero Kleindienst Gavin J. Pringle 《Icarus》2012,218(1):666-687
During the first and second Mercury flyby the MESSENGER spacecraft detected a dawn side double-current sheet inside the Hermean magnetosphere that was labeled the “double magnetopause” (Slavin, J.A. et al. [2008]. Science 321, 85). This double current sheet confines a region of decreased magnetic field that is referred to as Mercury’s “dayside boundary layer” (Anderson, M., Slavin, J., Horth, H. [2011]. Planet. Space Sci.). Up to the present day the double current sheet, the boundary layer and the key processes leading to their formation are not well understood. In order to advance the understanding of this region we have carried out self-consistent plasma simulations of the Hermean magnetosphere by means of the hybrid simulation code A.I.K.E.F. (Müller, J., Simon, S., Motschmann, U., Schüle, J., Glassmeier, K., Pringle, G.J. [2011]. Comput. Phys. Commun. 182, 946–966). Magnetic field and plasma results are in excellent agreement with the MESSENGER observations. In contrast to former speculations our results prove this double current sheet may exist in a pure solar wind hydrogen plasma, i.e. in the absence of any exospheric ions like sodium. Both currents are similar in orientation but the outer is stronger in intensity. While the outer current sheet can be considered the “classical” magnetopause, the inner current sheet between the magnetopause and Mercury’s surface reveals to be sustained by a diamagnetic current that originates from proton pressure gradients at Mercury’s inner magnetosphere. The pressure gradients in turn exist due to protons that are trapped on closed magnetic field lines and mirrored between north and south pole. Both, the dayside and nightside diamagnetic decreases that have been observed during the MESSENGER mission show to be direct consequences of this diamagnetic current that we label Mercury’s “boundary-layer-current“. 相似文献
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NLTE calculations of carbon abundance in Peg atmosphere revealed a slight deficiency of this element ([C/H] =–0.25). A short discussion of this result is given. The list of CII that could be used for LTE calculation of carbon abundance in hot stars is presented. 相似文献
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Zdenek Sekanina 《Icarus》1978,33(2):415-427
A model is proposed for single close encounters between two small masses, m1and m2, which orbit a much larger mass, M. The main new feature of the model is the assumption of conic motion of the center of mass of m1and m2 in the gravitational field of M. Comparisons of the model with the three-body equations of motion indicate that the model is a useful approximation for m1, m2 ? 10?5M. The model is therefore applicable for encounters between bodies of the order of an earth mass or smaller in the presence of the sun. Comparisons are also made of outcomes obtained by the model with outcomes of numerical integration for a large variety of close encounters. The above comparisons reveal that for many purposes the model is an adequate approximation for those encounters with ? ≥ 4, where ? is the eccentricity of the hyperbolic orbit of m1about m2. 相似文献
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