Light variations of massive stars (alpha Cyg variables). XV. The LMC supergiants R99 (LBV), R103, R123 (LBV) and R128

VBLUW photometry (Walraven system) of the four variable LMC supergiants R99, R103, R123 and R128 is analysed, searched for periods and discussed. Based on former and present photometry we conclude that two of the three emission-line objects are undoubtedly active LBVs (R99 and R123), although not so spectacular. R123, like AG Car near minimum brightness, shows a low amplitude S Dor activity with superimposed alpha Cyg-type variations. Based on observations obtained at the European Southern Observatory at La Silla, Chile