منابع مشابه
Do All Flares Have White Light Emission?
High-cadence, multiwavelength optical observations of a solar active region (NOAA 10969), obtained with the Swedish Solar Telescope, are presented. Difference imaging of white light continuum data reveals a white light brightening, 2 min in duration, linked to a co-temporal and co-spatial C2.0 flare event. The flare kernel observed in the white light images has a diameter of 300 km, thus render...
متن کاملDo Herbig Ae / Be stars have discs ?
Hα spectropolarimetry on Herbig Ae/Be stars shows that the innermost regions of intermediate mass (2 – 15 M⊙) Pre-Main Sequence stars are flattened. This may be the best evidence to date that the higher mass Herbig Be stars are embedded in circumstellar discs. A second outcome of our study is that the spectropolarimetric signatures for the lower mass Herbig Ae stars differ from those of the hig...
متن کاملWhy Do the Main Sequence Stars Have Similar Chemical Composition?
In this short note we have reconsidered the Jeans criterion for gravitational contraction of a gas nebula at different temperatures, from the present-day background radiation temperature (2.8 K) to those which existed at the early stage of the Universe. We demonstrate that the initial mass of quasars cannot be of the order of single galaxy masses, but rather 10 solar mass only. If they have lar...
متن کاملMagnetic Flares on Asymptotic Giant Branch Stars
We investigate the consequences of magnetic flares on the surface of asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind, in the winds of AGB stars the gas cooling time is much shorter than the outflow time. As a result, we predict that energetic flaring should enhance, rather than inhibit, dust formation around AGB stars. Analysis of an archival ROSAT X-ray spectrum ...
متن کاملDiffusion and Settling in Ap/Bp Stars
Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The physics of diffusion in these stars are reviewed briefly and some model predictions are discussed. While models reproduce some observations reasonably well, mor...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1993
ISSN: 0252-9211
DOI: 10.1017/s0252921100020716