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L. L. Cross, B. J. Wills (Astronomy Dept., University of Texas--Austin)
We have monitored the broad-band spectral polarization and flux density of 3C 273 during a time of outburst over two weeks in 1988 February. Simultaneous measurements in U, B, V, R, I, J, H, and K bands were obtained over several successive nights. One polarization observation in the L\prime band exceeded 4%; 3C 273 is a highly polarized quasar!
We show the complex time-dependence of the polarized flux density spectrum and wavelength-dependent position angle. Because of the low polarization of 3C 273, correction for the interstellar polarization is important. We are able to model most of our corrected polarized flux and position angle spectra with two power-law components separated by approximately 90\deg in position angle. The infrared data provide important constraints on these models. The flatter spectrum component, which dominates in the optical, is parallel to the VLBI jet. This angle is consistent with the reported "preferred" quiescent position angle of 3C 273.
Based on the luminosity of 3C 273 in extended radio emission, we argue that the low-polarization "Big Blue Bump" is not the reason for the low percentage polarization of this object, but rather that the optical synchrotron emission is weak, probably a result of low relativistic beaming into the line-of-sight.