Variability of luminous blue variables. I. Intermediate-band photometry An extensive photometric dataset has been compiled for six Luminous BlueVariables (LBVs). The dataset comprises published and unpublishedmeasurements in the Stroemgren, Geneva and Walraven photometric systems.The measurements within each individual system are presented in auniform manner. Combining observations from these three photometricsystems, a V_J_ light curve has been constructed for each LBV.Examination of the light curves reveals variations on widely differentmagnitude and time scales.
Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986) This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
Instrumental effects and the Stroemgren photometric system The extent to which the use of different photometers can affect resultson stellar color indices was investigated by simultaneously observing asample of widely different stars with several uvby photometric systemsavailable at the ESO, La Silla, Chile. In one instance, the ESO 50-cmtelescope and the four-channel photometer at the Danish 50-cm telescopewere used simultaneously. The reductions were performed separately oneach data set, using a linear color transformation procedure. Theresults agree with theoretical investigations which showed thatsubstantial errors can arise from the nonconformity of passbands. It isemphasized that it is necessary to use separate color transformationsfor various stellar types and classes and for different interstellarreddenings.
Search for variability in hydrogen-poor stars. I - Preliminary results of photoelectric observations for six stars The evolutionary status of hydrogen-poor stars is assessed.Photoelectric observations of six objects are reported as a first stepin a long-term project devoted to a search for variability of a largesample of hydrogen-poor stars. The observed stars exhibit phenomena ofmicrovariability with an amplitude of the order of 0.1m or less. Twoextreme helium stars are examined: a period in the range of0.162d-0.164d is found for BD + 10 deg 2179 with P = 0.1079962d for BD +13 deg 3324. It is noted that the mass-losing O subdwarf (sdO) BD = + 37deg 443 exhibits short-term fluctuations with a time-scale of severalminutes and long-term variations on a scale of months.
