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991.
U. Hwang R. Petre A. E. Szymkowiak S. S. Holt 《Journal of Astrophysics and Astronomy》2002,23(1-2):81-87
We present a newChandra observation of Tycho’s supernova remnant with the Advanced CCD Imaging Spectrometer. Multicolor Xray imaging reveals new
details of the outer shock and ejecta. At energies between 4 and 6 keV, the outline of the outer shock is clearly revealed
in X-rays for the first time. The distribution of the emission from lines of Si and Fe are confirmed to have a different morphology
from each other, and the Si ejecta are shown to extend to the blast shock at several locations. Characteristic spectra of
the outer shock and ejecta are also presented. 相似文献
992.
993.
In this paper we demonstrate the importance of cosmic rays for the dynamics of the interstellar medium. We present the first
3D-MHD numerical simulations of the Parker instability triggered by cosmic rays accelerated in supernova remnants. We show
that in the presence of galactic rotation a net radial magnetic field is produced as a result of the cosmic ray injection.
This process provides a very efficient magnetic field amplification within the general frame of so called fast galactic dynamo proposed by Parker (1992).
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
994.
S. Gallerani T. Roy Choudhury A. Ferrara 《Monthly notices of the Royal Astronomical Society》2006,370(3):1401-1421
995.
996.
G.B. Taylor F. Govoni S.W. Allen A.C. Fabian 《Monthly notices of the Royal Astronomical Society》2001,326(1):2-10
We present multifrequency VLA observations of the two radio galaxies 3C 129 and 3C 129.1 embedded in a luminous X-ray cluster. These radio observations reveal a substantial difference in the Faraday Rotation Measures (RMs) toward 3C 129.1 at the cluster centre and 3C 129 at the cluster periphery. After deriving the density profile from available X-ray data, we find that the RM structure of both radio galaxies can be fitted by a tangled cluster magnetic field with strength 6 μG extending at least 3 core radii (450 kpc) from the cluster centre. The magnetic field makes up a small contribution to the total pressure (5 per cent) in the central regions of the cluster. The radio morphology of 3C 129.1 appears disturbed on the southern side, perhaps by the higher pressure environment. In contrast with earlier claims for the presence of a moderately strong cooling flow in the 3C 129 cluster, our analysis of the X-ray data places a limit on the mass deposition rate from any such flow of < 1.2 M⊙ yr−1 . 相似文献
997.
We have carried out multi-station TV observations since 1994 in order to determine the orbit of the Arietid daytime meteor
stream. In 1999, one possible Arietid meteor was recorded by our simultaneous observations and its orbit was determined. In
2003, two Arietid meteors were observed from two stations of our observing site, those orbits were determined precisely, the
orbital elements were in good agreement with each other. This is the first time that determination of the precise orbit of
the Arietids has been made from optical observations. The orbit of these Arietid meteors, and comparison with the orbit obtained
from radar observations are discussed. 相似文献
998.
Michael Stein 《Mathematical Geology》1987,19(5):387-405
Suppose a multi-Gaussian process is observed at some set of sites, and we wish to obtain the conditional block grade distribution given some observations. We show that this conditional distribution is approximately Gaussian under certain conditions. In particular, given a single observation from a continuous multi-Gaussian process, the conditional distribution under a small change of support is approximately Gaussian unless, roughly speaking, the observed process is twice differentiable and the observation site is at the center of mass of the support region. A Gaussian approximation for the conditional prediction error of the total ore in a fixed region is considered also, although an example demonstrates that a naive analysis can give incorrect limiting conditional means. 相似文献
999.
A procedure is proposed that employs first-moment estimation (kriging), cross-validation, and response surface analysis to estimate parameters of a generalized covariance function. Results from application of this procedure to two data sets are given. 相似文献
1000.