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21.
Jacco Vink 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):503-511
In this paper I discuss the lack of observational evidence that magnetars are formed as rapidly rotating neutron stars. Supernova remnants containing magnetars do not show the excess of kinetic energy expected for such a formation scenario, nor is there any evidence for a relic pulsar wind nebula. However, it could be that magnetars are formed with somewhat slower rotation periods, or that not all excess rotational energy was used to boost the explosion energy, for example as a result of gravitational radiation. Another observational tests for the rapid initial period hypothesis is to look for statistical evidence that about 1% of the observed supernovae have an additional 1040–1044 erg/s excess energy during the first year, caused by the spin down luminosity of a magnetar. 相似文献
22.
Satoru Katsuda Hiroshi Tsunemi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):383-389
We have observed the Cygnus Loop from the northeast (NE) to the southwest (SW) with XMM-Newton. We extracted spectra from 3′-spaced annular regions across the Loop and fitted them either with a one-kTe-component non-equilibrium ionization (NEI) model or with two-kTe-component NEI model. We found that the two-kTe-component model yields significantly better fits in almost all the spectra than the one-kTe-component model. Judging from the abundances, the high-kTe-component in the two-temperature model must be fossil ejecta while the low-kTe-component comes from the swept-up interstellar medium (ISM). The distributions of Ne, Mg, Si, and S for fossil ejecta appear to retain the onion-skin structure at the time of a supernova explosion, suggesting that significant overturning of the ejecta has not occurred yet. Comparing the relative abundances of fossil ejecta estimated for the entire Cygnus Loop with those from theoretical calculations for Type-II SN, the mass of the progenitor star is likely to be ∼13 M⊙. The trends of the radial profiles of kTe and emission integral for the swept-up ISM are adequately described by the Sedov model, suggesting that the swept-up ISM is concentrated in a shell-like structure. Comparing our data with the Sedov model, we found the ambient medium density to be ∼0.7 cm−3. Then, we estimated the total mass of the swept-up ISM and the age of the remnant to be ∼130 M⊙ and 13,000 years, respectively. Note that if the explosion occurred within a stellar wind cavity, then the density in the cavity, the total swept-up mass in the cavity, and the age of the remnant are estimated to be ∼0.14 cm−3, ∼25 M⊙, and ∼10,000 years, respectively. 相似文献