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Wink J. E. Altenhoff W. J. Bieging J. Butler B. Butner H. Haslam C.G.T. Kreysa E. Martin R. Mauersberger R. McMullin J. Muders D. Peters W. Schmidt J. Schraml J. B. Sievers A. Stumpff P. Von Kapp-Herr A. Thum C. Zylka R. 《Earth, Moon, and Planets》1997,77(3):165-165
Earth, Moon, and Planets - The concept of simultaneous multifrequency continuum observations, successfully tested on Comet Hyakutake, was applied to Comet Hale-Bopp, using the Heinrich Hertz... 相似文献
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J. E. Wink W. J. Altenhoff J. Bieging B. Butler H. Butner C.G.T. Haslam E. Kreysa R. Martin R. Mauersberger J. McMullin D. Muders W. Peters J. Schmidt J. B. Schraml A. Sievers P. Stumpff A. Von Kapp-Herr C. Thum R. Zylka 《Earth, Moon, and Planets》1997,77(3):165
The concept of simultaneous multifrequency continuum observations, successfully tested on Comet Hyakutake, was applied to
Comet Hale-Bopp, using the Heinrich Hertz Submillimeter Telescope (HHT) with the four color bolometer between 250 and 870
GHz, the IRAM 30m telescope at 240 Ghz, the MPIfR 100-m telescope at 32 GHz, and the IRAM interferometer near 90 and 240 GHz.
Near-simultaneous measurements were done between February 15 and April 26, 1997, mainly concentrated in mid March shortly
before perigee of the comet.
The measurements gave the following preliminary results:
Interferometer detection of the nuclear thermal emission. If the signal at the longest interferometer spacing of 170 mis due
to thermal emission from the nucleus only, its equivalent diameter is ∼49 km. If, however, this signal contains a contribution
from a strongly centrally peaked halo distribution(e.g., r−2 density variation) the diameter may be as low as 35 km. The emission found interferometrically was always 5″ north and 0.1
sec east from the position predicted by Yeoman's solution 55.The comparison of the interferometric continuum emission with
the simultanously obtained molecular line observations (reported on this conference) shows the origin of the strongest line
emission concentrated on the nucleus. The 30-m observations show a radio halo with a gaussian FWHP of ∼11, corresponding to
a diameter of 11000 km at geocentric distance of 1.2 a.u.
A spectral index of ∼3.0 for the total signal, which may indicate a smaller mean particle size than for Hyakutake. Assuming
an average cometary density of 0.5 gcm−3, the mass contained in the nucleus is ∼1$#x2013;3 1019 g and 1012 g in the particle halo.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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The physicochemistry of the Black River and adjacent marine beach, in terms of tidal, daily and seasonal fluctuations of temperature and salinity, presents a highly stressed environment exacerbated by canalization of the river mouth. Riverine pollution further stresses this environment, producing low densities and diversities of marine infauna adjacent to the river. No fauna were found in the river mouth where typical estuarine conditions exist only during high tide. Tolerance of the dominant marine species, Cerebratulus fuscus, to temperature, salinity and river water combinations showed that mortality was more rapid after exposure to river water dilutions than after exposure to distilled water dilutions. Computer-generated models suggested that this species should survive conditions closer to the river than were observed. This confirmed additional stress due to pollution carried in the river from urban and industrial drainage. Lower river water temperatures during winter appear to ameliorate pollution stress, enhancing survivability of the infauna. 相似文献
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New 250 GHz flux density measurements with the 30 m telescope at Pico Veleta are presented for 3 Be stars. We suggest that the radio spectral indexis typically close to 1.4 for these stars. We present in a discusssion of own and literature data some evidence that in few cases slow variations with a time scale of about a year occur. Both evidence is compatible with the idea that there is no stellar activity type radio emission of Be stars but a may be slightly modulated quiescent radiation of the outer parts of selfsimilar circumstellar disks. An immediate improvement of existing models is not possible. 相似文献
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