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Paper: Determination of Variable Time Delay in Uneven Data Sets
Volume: 125, Astronomical Data Analysis Software and Systems VI
Page: 162
Authors: Oknyanskij, V. L.
Abstract: Time delay determinations in astrophysics are used most often to find time delays between flux density variations in different spectral bands and/or lines in AGNs, and different images of gravitationally lensed QSOs. Here we consider a new algorithm for a complex case, when the time delay is itself a linear function of time and the intensity of echo response is exponential function of the delay. We apply this method to the optical-to-radio delay in the lensed double quasar Q0957+561. Radio-optical variability correlation in Q0957+561 was first reported by Oknyan\-skij & Beskin (1993, hereafter OB) on the basis of radio observations made in the years 1979 to 1990. OB used an idea to take into account the known gravitational lensing time delay to get combined radio and optical light curves and then to use them for determination of the possible radio-from-optical time delay. It was found this way that radio variations (5MHz) followed optical ones by about 6.4 years with high level of correlation (~ 0.87). Using new radio data (Haarsma et al. 1997), for the interval 1979--1994, we find nearly the same value for the optical-to-radio delay as had been found before. Additionally, we suspect that the time delay value is linearly increasing at about 110 days per year while the portion of reradiated flux in the radio response is decreasing. We conclude that the variable radio source is ejected from the central part of the QSO compact component.
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