V.L.Oknyanskij
Sternberg State Astronomical Institute
Time delay determinations in astrophysics is used most often to find time shifts between variations of different spectral bands and/or spectral lines in AGNs as well as time delays between different images of gravitationally lensed QSOs. In most of the cases the task is complicated by unevenly spacing of data sets and classical cross-correlation methods become useless. Here we consider a new algorithm for more complex case, when the time delay is a linear function of time and portion of intensity in the response is a power function of the delay. We apply this method to QSO 0957+561, which is the famous double quasar, a generally accepted case of gravitational lensing. Radio-optical correlation in the Q0957+561 was first preliminary reported by Oknyanskij & Beskin (1993) on the base of radio observation during 1979-1990. Using new radio data (Haarsma et al. 1996), we have got for interval 1979-1994 nearly the same value of the optical-to-radio delay (about 6.4 years) as it had been found before. Additionally we suspect that the time delay value linearly increased and the portion of reradiated in the radio-response flux decreased with time. New results give opportunities for physical constrains on the radio source: velocity, size, location. We have made a conclusion that the variable radio source is ejected from the central part of the QSO compact region.