SIMBAD references

The possibility that stars of the upper main sequence possess weak winds (of order 10^–14 to 10^–12M_☉/yr) that may compete with atomic diffusion has been suggested by several authors, particularly by Babel & Michaud (1991ApJ...366..560B) and Babel (1992A&A...258..449B). Such winds may affect the chemical abundances that appear in the atmospheres of these stars. However, obtaining unambiguous evidence for the existence of a weak wind is not easy. We consider the possibility that naturally abundant chemical elements such as C, O and Ne, which are not expected to be made overabundant in a stellar atmosphere by radiative levitation, may accumulate in or near the photosphere of a mass-losing star, thus serving as tracers of mass loss. We first show that the most abundant elements are not expected to be overabundant in the atmospheres of main sequence stars in the range 8000≤T_e≤15000K due to radiative acceleration. We next show that hydrogen mass loss from the atmosphere, at a rate in the range of roughly 10^–14≤{dot}(M)≤10^–12M_☉/yr, could lead to accumulation of a few abundant elements in or not far below the stellar photosphere, provided that any turbulence in the wind at the level of the photosphere is not sufficient to prevent diffusion. We find that such mass loss in late B stars should lead to observable overabundance of Ne, while in early A stars, such mass loss causes O to accumulate in the atmosphere. Detection of overabundances of these elements would provide direct evidence of the presence of weak mass loss. The few available Ne abundance determinations do not allow us to decide whether such weak winds are present in any B stars, but numerous measurements of O abundance imply that either winds in this mass loss range do not occur, or else that atmospheric diffusion is prevented by turbulence in early A stars.