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Träfflista för sökning "WFRF:(Witzel T.) ;pers:(Bååth L.B. 1948)"

Sökning: WFRF:(Witzel T.) > Bååth L.B. 1948

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1.
  • Marcaide, J. M., et al. (författare)
  • Discovery of shell-like radio-structure in SN1993J
  • 1995
  • Ingår i: Nature. - London : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 373:6509, s. 44-45
  • Tidskriftsartikel (refereegranskat)abstract
    • SUPERNOVA explosions are poorly understood, partly because of difficulties in modelling them theoretically(1), and partly because there have been no supernovae observed in our Galaxy since the invention of the telescope. But the recent discovery(2) of supernova SN1993J in the nearby galaxy M81 offers an opportunity to investigate the evolution of the remnant, and its interaction with the surrounding interstellar medium, at high resolution. Here we present radio observations of SN1993J, made using very-long-baseline interferometry, which show the development of a shell structure. This 8-month-old radio shell is the youngest ever discovered in a supernova. The data suggest that the supernova explosion and the expanding shell of the remnant have nearly spherical symmetry, with small deviations where some parts of the shell are brighter than others. If these deviations arise because of variations in the density of the shell, this may reconcile earlier reports of symmetric radio emission(3) with the observed optical asymmetry(4,5), as the density variations could easily cause the latter. We infer that the radio emission is generated at the interface(6-9), where the surrounding gas is shocked by the ejecta.
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3.
  • Standke, K. J., et al. (författare)
  • High Sensitivity VLBI at 86 GHz : First Fringes with the 100 m Radio Telescope at Effelsberg
  • 1993
  • Ingår i: VLBI Technology. - Tokyo : Terra Scientific. - 4887041128 ; , s. 75-85
  • Bokkapitel (refereegranskat)abstract
    • Inclusion of large and sensitive antennas is of essential importance to further improve the imaging capabilities of VLBI at 3.5 mm wavelength. The combination of the 100 m radio telescope at Effelsberg (illuminated diameter ~60 m at lambda = 3.5 mm) with the 30 m radio telescope at Pico Veleta presently allows the detection of compact flux down to a level of 0.2 Jy (for τ=360 seconds integration time). Fringes have been found for 23 radio sources many of them not observed previously with VLBI at 86 GHz. On European baselines to Effelsberg the SNR typically was 10 to 30 (and ranged up to 107 for 3C279), facilitating model fitting for the brightest sources. Even in spite of chaning weather conditions during the observations (coherence times ranged between 10 to 100 seconds) and a still non-optimum pointing model for the 100 m antenna for observations at high frequencies, these results demonstrate that the 100 m radio telescope can be successfully incorporated in global VLBI experiments at 3.5 mm wavelength.
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