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41.
We study analytically the Rayleigh–Taylor instability in expanding supernova gas shell. The instability appears at the inner
shell surface accelerated by blowing pulsar wind. The most dangerous perturbations correspond to wavelengths comparable to
the shell thickness. We analyze the fragility of the supernova remnant shell in function of the initial perturbation amplitude
and the shell thickness. 相似文献
42.
Astronomy Letters - We analyze the physical processes that should be taken into account when modeling young type-Ia supernova remnants (SNRs) with ages of several hundred years in which forward... 相似文献
43.
44.
W. W. Tian M. Haverkorn † H. Y. Zhang 《Monthly notices of the Royal Astronomical Society》2007,378(4):1283-1286
New images of the supernova remnant (SNR) G351.7+0.8 are presented based on 21-cm H i -line emission and continuum emission data from the Southern Galactic Plane Survey. SNR G351.7+0.8 has a flux density of 8.4 ± 0.7 Jy at 1420 MHz. Its spectral index is 0.52 ± 0.25 ( S = v −α ) between 1420 and 843 MHz, typical of adiabatically expanding shell-like remnants. H i observations show structures possibly associated with the SNR in the radial velocity range of −10 to −18 km s−1 , and suggest a distance of 13.2 kpc and a radius of 30.7 pc. The estimated Sedov age for G351.7+0.8 is less than 6.8×104 yr . A young radio pulsar PSR J1721−3532 lies close to SNR G351.7+0.8 on the sky. The new distance and age of G351.7+0.8 and recent proper motion measurements of the pulsar strongly argue against an association between SNR G351.7+0.8 and PSR J1721−3532. There is an unidentified, faint X-ray point source 1RXS J172055.3−353937 which is close to G351.7+0.8. This may be a neutron star potentially associated with G351.7+0.8. 相似文献
45.
46.
S. Jane Arthur 《Astrophysics and Space Science》2002,281(1-2):267-270
The radiation produced by the gas cooling behind a fast supernova remnant shock in the interstellar medium is capable of ionizing
the undisturbed medium ahead of the shock wave. In this work I investigate the nonequilibrium evolution of these photoionized
precursor regions by means of radiation-hydrodynamic simulations of supernova remnant evolution.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
47.
The compact source 0125 + 628 in the centre of the galactic supernova remnant G 127.1 + 0.5 has been re-observed in HI absorption
using the Westerbork Synthesis Radio Telescope (WSRT). The outer arm HI absorption atV = -95km s-1 has been confirmed. The absorption spectrum is similar to that of the nearby extragalactic source 0123 + 633. We discuss
the arguments concerning an extragalactic origin of 0125 + 628 and conclude that it is most likely extragalactic and not an
SS 433 type object.
The National Radio Astronomy Observatory is operated by Associated Universities Inc. under contract with the National Science
Foundation. 相似文献
48.
Satyendra Thoudam 《Monthly notices of the Royal Astronomical Society》2007,378(1):48-54
We study in detail the effect of different particle release times from sources on the cosmic ray (CR) spectrum below 1015 eV in the Galaxy. We discuss different possible forms of particle injection such as burst-like injection, continuous injection for a finite time, injection from a stationary source and energy-dependent injection. When applied to the nearby known supernova remnants, we find that the observed CR anisotropy data favour the burst-like particle injection model for the CR diffusion coefficient D ( E ) ∝ E a with a = 0.3 –0.6 in the local region. In this study we have also found that the contribution of the sources G114.3+0.3 and Monogem dominate if the observed anisotropy is a result of the effect of the nearby sources. Further study shows that we should not neglect the contribution of the undetected old sources to the local CR anisotropy. 相似文献
49.
Rural Hong Kong contains culturally protected enclaves of remnant woodlands that provide sanctuary for vegetation, wildlife and soil. This study focuses on the influence of natural and cultural factors on soil properties in woodlands with different human activities. At each of the nine selected sites, two pits were dug to collect soil samples for analysis of 24 physical and chemical properties. Analyses of variance between soil attributes and site factors suggest the prominence of woodland size, and important contribution of topography, aspect and parent material. Soil indicators of human impacts and the tenacity of woodland soil towards anthropogenic disturbance were demonstrated. 相似文献
50.
R. Soria R. P. Fender D. C. Hannikainen A. M. Read I. R. Stevens 《Monthly notices of the Royal Astronomical Society》2006,368(4):1527-1539
We studied the radio source associated with the ultraluminous X-ray source in NGC 5408 ( L X ≈ 1040 erg s−1 ) . The radio spectrum is steep (index ≈−1 ), consistent with optically thin synchrotron emission, not with flat-spectrum core emission. Its flux density (≈0.28 mJy at 4.8 GHz, at a distance of 4.8 Mpc) was the same in the March 2000 and December 2004 observations, suggesting steady emission rather than a transient outburst. However, it is orders of magnitude higher than expected from steady jets in stellar-mass microquasar. Based on its radio flux and spectral index, we suggest that the radio source is either an unusually bright supernova remnant, or, more likely, a radio lobe powered by a jet from the black hole (BH). Moreover, there is speculative evidence that the source is marginally resolved with a radius ∼30 pc. A faint H ii region of similar size appears to coincide with the radio and X-ray sources, but its ionization mechanism remains unclear. Using a self-similar solution for the expansion of a jet-powered electron–positron plasma bubble, in the minimum-energy approximation, we show that the observed flux and (speculative) size are consistent with an average jet power ≈ 7 × 1038 erg s−1 ∼ 0.1 L X ∼ 0.1 L Edd , an age ≈105 yr, a current velocity of expansion ≈80 km s−1 . We briefly discuss the importance of this source as a key to understand the balance between luminosity and jet power in accreting BHs. 相似文献