The X-ray spectrum of the highly polarized quasar PKS 1502+106

We report the detection and spectrum of the distant (z = 1.839), highly polarized quasar PKS 1502+106 in the X-ray band based on data collected over the period 1990-1994 using ROSAT and ASCA. We find the source to exhibit intensity variations of a factor ≳2 at 1 keV on timescales of years, small compared to the variability observed historically in the radio, millimeter, and optical bands. The (energy) spectral index is found in the range 0.4 ≲ α X ≲ 0.8 (at 90% confidence). Its multiwaveband spectral index is broadly consistent with other highly polarized quasars (HPQs). From the application of an inhomogeneous synchrotron self-Compton (SSC) jet we find that a model similar to that proposed for 3C 279 is consistent with the multiwaveband spectrum. We suggest that a change in the energy injection and/or transport mechanisms within such a jet could easily result in PKS 1502+106 being detectable at γ-ray energies.