A photometric survey of stars with circumstellar material

We present the result of a follow-up Stromgren photometric survey of sixteen southern bright stars with circumstellar material, in order to detect possible weak photometric variations. We found new variations of the $\beta~\:$Pictoris brightness from 1999 to 2002 with a weak long-term variation of ~$-0.8\times 10^{-3}$ mag per year, over about 3 years. These variations look similar to those seen from 1975 to 1981 and from 1995 to 1998 (Nitschelm et al. 2000, A&AS, 145, 275). They can be due to differential occultation by dust inhomogeneities transiting the star through the years. We detected new periodic variations for HD 256 (HR 10) with periods ranging from 0.35 day to 6.69 days during several months. These variations may also be interpreted in terms of variable obscuration due to structures in the circumstellar disk suspected to be surrounding this star.