An analysis of the incidence of the Vega phenomenon among main-sequence and post main-sequence stars

During the past decade, the incidence of the Vega phenomenon has been studied several times statistically, but these studies lack a sufficiently rigorous basis. To improve the discussion, we selected a sample of objects with detectable photospheric fluxes, in casu at 60 mu m. Because of the limited sensitivity of IRAS, only a small fraction of the main-sequence stars within 25 parsec from the Sun meet this condition and the sample contains too few objects for a reliable estimation of the fraction of excess stars. We estimate the incidence of the Vega phenomenon by applying robust statistical methods, in casu the Least Median of Squares regression and the Minimum Volume Ellipsoid method, and survival analysis. We find a very similar result for main-sequence stars and their descendants, the first-ascent G-K giants. 13 +/- 10% of the main-sequence stars show a 60 mu m excess and 14 +/- 5% of the giants.