J/A+AS/116/1 J/A+AS/116/1 UBV photometry of MWC560 T Tomov D Kolev M Ivanov A Antov A Jones M Mikolajewski A Lepardo R Passuello S Saccavino G Sostero T Valentinuzzi Y Bellas-Velidis A Dapergolas U Munari Astron. Astrophys. Suppl. Ser. 116 1 1996 1996A&AS..116....1T J/A+AS/122/43 : V694 Mon plate spectra (Tomov+ 1997) Photometry, UBV Stars, variable binaries: close binaries: symbiotic stars: individual (MWC 560) stars: magnetic fields stars: mass-loss We present results of an extensive photometric monitoring campaign of the peculiar emission star MWC 560 that covers the range 1990-1995. The time interval corresponds to the length of the proposed orbital period of this highly peculiar binary, which attracted considerable interest in January-April 1990, when absorption components, shifted by -6000km/s from corresponding emission lines, were observed. Here we present photometric data secured during: 113 nights of conventional UBV photoelectric photometry, 45 nights of high speed UBV photoelectric photometry to study the flickering activity, and 682 visual photometric estimates. MWC 560 has experienced a decrease in magnitude since the bright (V=9.2mag) phase in 1990. After the minimum reached in May 1994 (V=10.7mag), the star is currently increasing slowly in brightness. The decrease has been accompanied in all bands by large fluctuations superimposed on the mean trend. The B-V colour has shown a steady increase by 0.0.33mag/yr. U-B has remained stable at -0.07mag since late 1990. In all the observing nights devoted to high speed photometry we observed flickering activity in MWC 560. The data show that the flickering amplitude {DELTA}U increases with the decrease of the U magnitude. Quasi-periodic variations have always been detected. A period of ~70min has been observed in ~13 nights which is close to the ~60min quasi-period reported by Michalitsianos et al. (1993). However, no coherent variability is traceable throughout the whole set of flickering data.

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JD Date of the observation d Vmag Star's magnitude in V band mag u_Vmag Uncertainty flag on Vmag --- B-V B-V colour mag u_B-V Uncertainty flag on B-V --- U-B U-B colour mag u_U-B Uncertainty flag on U-B --- o_Vmag Number of independent measurements --- Obs Identification of the Observatory number=1 The observatories are: Roz = Bulgarian National Astronomical Observatory Rozhen, Bel = Belogradchik Astronomical Observatory, Kry = Kryoneri Observatory in Greece, Tor = Torun Observatory in Poland, Ols = Olsztyn Observatory in Poland, Suh = Mt. Suhora Observatory in Poland, Rem = Remanzacco Observatory of the Assoziazione Friulana di Astronomia e Meteorologia (Italy). --- JD Date of the observation d Vmag Visual brightness estimates mag Patricia Bauer CDS 1996Jan15T. Tomov, <rozhen@tempus.tu-plovdiv.bg> J_A+AS_116_1.xml