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K. S. Stankevich A. M. Aslanyan V. P. Ivanov R. M. Martirosyan Ye. Terzian 《Astrophysics》2003,46(4):429-433
Radio emission of the historical supernovae remnants Tycho (SNR1572) and Kepler (SNR1604) and evolution of their luminosity are considered. Measurement data of secular luminosity decrease rate, obtained earlier by the authors, were corrected with account of variation in time of the flux density of the reference sources. As a result, it is found that the SNR1604 luminosity at 1667 MHz is weakening with an annual mean rate equal to (0.2 ± 0.07)%. The corresponding rate for SNR1572 is (0.47 ± 0.05)%. Since the radio luminosity evolution, as well as energy densities of magnetic field and relativistic electrons inside SNR1604 and SNR1572 are essentially different, these remnants should be considered as different types of supernovae. Bandiera classified SN1604 as type SNIb or SNII. 相似文献
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Yervant Terzian 《Astrophysics and Space Science》1969,3(4):479-489
Radio observations of emission nebulae at 74 MHz are reported. Flux densities for NGC 1499, IC 405, IC 410, NGC 2024, NGC 2175, NGC 2237-46, and NGC 6820 are given. Most of the observed nebulae are found to be optically thick at 74 MHz. Combining the low frequency results with previously measured flux densities at high frequencies, it is shown that it is possible to derive the mean electron temperatures of the observed nebulae. The results show that the range in temperature is from 3200 to 6800 K. 相似文献
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IUE ultraviolet spectral recording for a low excitating planetary nebula NGC 6369 is obtained. The very strong doublet 2800 Mgii in emission as well as not less strong absorption line 2852 Mgi are discovered in the spectrum of this nebula. It is shown that the resonance line 2852 Mgi may originate only in a neutral envelope, around the nebula, consisting of neutral hydrogen, neutral magnesium, and dust particles (Hi+Mgi). The importance of this absorption line as a powerful indicator of the discovery of neutral envelopes around the planetary nebulae is outlined.The possibility of the existence of one more envelope—transition zone—immediately contacting with the bright that is ionized part of nebula (Hii+Mgii) is also shown. The transition zone consists of neutral hydrogen, ionized magnesium, and dust particles (Hi+Mgii), main parameters of this zone are also obtained (Table IV).The temperature of the central star of this nebula is obtained for the first time:T
*=48000 K. Continuous background in the interval 2600–3000 Å is identified with Balmer continuum with electron temperatureT
e
=12500 K. 相似文献
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High signal to noise neutral hydrogen observations of a complete sample of 132 galaxy pairs show a velocity difference distribution which decreases monotonically from zero. There is no strong indication of redshift periodicity for the entire sample and no indication at all for a subset of 79isolated galaxy pairs. In addition, when redshifts are corrected for the solar motion around the Galactic Center there is no indication of a redshift periodicity of 37.6 km s–1 in V for galaxy pairs (as suggested by Guthrie and Napier 1996). 相似文献
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The relevant data for the known 147 pulsars are presented in graphical and tabular forms. Various data correlations are discussed, and a detailed analysis of pulsar dispersion measures and distances is given. The range of the electron densities in the diffuse interstellar medium is found to be 0.01 cm–3n
e0.1 cm–3, and n
e0.03 cm–3. The dispersion scale height for pulsars is found to be 5.9±0.7 pc cm–3 implying a linear scale height of 200 pc, which is much smaller than the electron scale height of our Galaxy.Astrophysics and Space Science Review Paper. 相似文献
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The Green Bank Equation for the number of communicative civilizations, N, in our Galaxy is reconsidered in view of recent information on the multiplicity of solar-type stars and the possibilities of forming habitable planets around them. Our results are contingent upon the statistical validity of Abt and Levy's work of stellar multiplicity and upon features of Heppen-heimer's theory of planet formation in binary systems. It is concluded that N may have been overestimated by a factor of at least 50. 相似文献
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E. Khachikian G. Ter-Kazarian L. Sargsyan K. Yerknapetyan Ye. Terzian 《Monthly notices of the Royal Astronomical Society》2006,368(1):461-470
We present a spectroscopic investigation of an unusual cluster of galaxies that contains galaxies Mrk 261 and 262 which have ultraviolet excess at the same redshift of about 0.03. We also study Mrk 266, which has a peculiar optical morphology and a binary nucleus. The nuclear components in both of these samples show quite similar emission lines in their spectra to Seyfert galaxy activity characteristics. The kinematics and physical properties of the gas in Mrk 266 allow a reliable mass estimate to be made assuming that the characteristic broad emission lines arise from the photoionization of the virialized clouds by the central ionizing nucleus. However, the nuclei masses would be overestimated if the radiation pressure and/or magnetic fields contribute significantly to the dynamics, or if the outflows or winds could cause the observed linewidths to exceed those induced by the nucleus potential alone. 相似文献
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We have obtained IUE ultraviolet spectra of the low-excitation planetary nebula CN 3-1. The recordings show the well-known doublet 2800 MgII and resonance line 2852 MgI as strong absorption lines. We show that these lines cannot be of interstellar origin and that they may be formed in two envelopes surrounding the main nebula: in the transition zone (doublet 2800 MgII) and in the neutral envelope (line 2852 MgI). These envelopes possess an important property: they contain dust particles, and even a moderate amount of such particles may influence the strength of the absorption lines of MgII and MgI.The emission line 4686 HeII has no relation to the nebula CN 3-1 and belongs to its nucleus, a star of type WR. It is very probable that the nucleus of this nebula is a binary system with a WR component (T
*=50 000 K), exciting the helium lines, and a star of B0 or B2 type (T
*=26 000 K) exciting the nebular linesN
1+N
2 [OIII], 3727 [OII], hydrogen lines, etc. 相似文献
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