Since March 1, 2001, we have been monitoring 3C 273 three times per week with RXTE, except for an 8-week period when it is too close to the sun in the sky. Below are plots of (1) the 2-20 keV X-ray and near-IR I-band light curves since 2004, and (2) the 2-10 keV and 10-100 keV X-ray light curves, complete up to January 2007. Here you can see that the X-rays vary on all time scales that we have sampled: a few days to months. Grandi & Palumbo (2004, Science, 306, 998) report that their observed X-ray iron emission line variability and changing X-ray spectral slope can be explained if the X-rays come both from the jet and from the accretion-disk region. In the future, we will add multiwavelength radio light curves. The ejections of (apparent) superluminal components (bright features in the jet) in 3C 273 are marked with upward arrows in the plot. We are trying to determine whether the appearance of new superluminal features is related to major X-ray flares, which is difficult given the large numbers of both types of events and the possibility of offets in time between radio and X-ray events that are not the same for different events. In light of the Grandi & Palumbo result, we will need to separate the jet and disk X-ray emission at each time. We will try to do this by using the RXTE HEXTE (high-energy X-ray detector) data, which should be mostly sensitive to changes in the jet emission. We do, though, generally see a strong correlation between the hard and soft X-ray flux, suggesting that the variability in soft X-rays may be mostly from time changes in the jet emission.
