The dependence of the characteristics of the brightness variability of Herbig Ae/Be stars on the orientation of their star-disk systems

We analyze the brightness variability of six Herbig Ae/Be stars: V1331 Cyg, LkH alpha 198 = V633 Cas, AS 442, XY Per, V517 Cyg, and WW Vul. The last t wo objects are UX Ori stars showing Algol-like brightness dips with amplitu des of 2.(m)0-2.(m)5. AS 442 and XY Per also exhibit brightness dips but wi th considerably lower amplitudes, 0.(m)3-0.(m)6. On the contrary, such dips are not present in the light curves of V1331 Cyg and LkH alpha 198, where stochastic variability with amplitudes of 0.(m)1-0.(m)2 on timescales of ab out a day can be seen. AS 442 and XY Per also show stochastic variability, but with lower amplitudes (approximate to0.(m)05). These different types of variability could be related to the orientations of the star-disk systems. We suggest that the brightness variations in young stars whose disks are v iewed edge-on are mainly due to non-uniform absorption, whereas the charact er of the variability in stars with pole-on disks is determined by non-stat ionary accretion. (C) 2001 MAIK "Nauka/Interperiodica".