Further photometric observations of the x-ray binary A0535+26/V725 Tau: A new activity cycle

We performed new photoelectric UBV observations of the X-ray binary A0535+26 at the Crimean Station of the Sternberg Astronomical Institute in 1998-2003. After the brightness stabilized at a minimum of about 500 days in duration, a new brightness rise steeper than that observed previously began: the brightness increased over two seasons of observations by a total amplitude of O(m)5. The physical parameters (T-e, n(e)) of the additional emission that caused this brightening match, within the error limits, were obtained from the averaged over 15 years, data, that include both the ascending and descending branches of the light curve. We found a delay of the variations in the Ha line relative to the continuum, which is no more than one year. (C) 2005 Pleiades Publishing, Inc.