Abstract

We present results from a 244 ks \$NuSTAR\$ observation of 3C 273, obtained during a cross-calibration campaign with the \$Chandra\$, \$INTEGRAL\$, \$Suzaku\$, \$Swift\$, and \$XMM-Newton\$ observatories. We show that the spectrum, when fit with a power-law model using data from all observatories except \$INTEGRAL\$ over the 1-78 keV band, leaves significant residuals in the \$NuSTAR\$ data between 30-78 keV. The \$NuSTAR\$ 3-78 keV spectrum is well-described by an exponentially cutoff power-law (\$\Gamma = 1.646 0.006\$, E\$\_cutoff = 202\_-34^+51\$ keV) with a weak reflection component from cold, dense material. There is also evidence for a weak (\$EW = 23 11\$ eV) neutral iron line. We interpret these features as arising from coronal emission plus reflection off an accretion disk or distant material. Beyond 80 keV \$INTEGRAL\$ data show clear excess flux relative to an extrapolation of the AGN model fit to \$NuSTAR\$. This high-energy power-law is consistent with the presence of a beamed jet, which begins to dominate over emission from the inner accretion flow at 30-40 keV. Modeling the jet as a power-law, we find the coronal component is fit by \$\Gamma\_AGN = 1.638 0.045\$, \$E\_cutfoff = 47 15\$ keV, and jet photon index by \$\Gamma\_jet = 1.05 0.4\$. We applied comptonizing coronal electron plasma models to place constraints on the plasma temperature and optical depth. Finally, we investigate the variability and find an inverse correlation between flux and \$\Gamma\$. We interpret this hardening of the spectrum with increasing flux to be due to the jet.

Tags

Users

  • @ericblackman

Comments and Reviews