Presented
at the 88th AAVSO Spring Meeting, July 3, 1999
Abstract
We have used the Hipparcos
database of epoch photometry to study the variability of several yellow
semiregular (SRd) variables. For some of the stars (V487 Cas, RW Cep, BM Sco,
CE Vir), the results were inconclusive. For SX Lac and TY Vir, the periods
found were consistent with the General Catalogue of Variable Stars (190
and 50 days, respectively). For UU Her, the known periods of about 45 and 72
days were recovered. For WY And, RU Cep, and SX Her, reliable periods were
found; we used archival data to construct (O-C) diagrams to study both random
and systematic period changes in these three stars.