Coronal properties of the Seyfert 1 galaxy 3C 120 with NuSTAR

Abstract

We present measurement of the cut-off energy, a proxy for the temperature of the corona in the nuclear continuum of the Seyfert 1 galaxy 3C 120 using $\sim$120 ks of observation from ${\it NuSTAR}$. The quality broad band spectrum from 3$-$79 keV has enabled us to measure the Compton reflection component (R) and to constrain the temperature of the coronal plasma. Fitting one of the advanced Comptonization models, ${\it compPS}$ to the observed broad band spectrum we derived the kinetic temperature of the electrons in the corona to be $kT_e = 25 \pm 2$ keV with Compton ${\it y}$ parameter of $y = 2.2 \pm 0.1$ for a slab geometry and $kT_e = 26_{-0}^{+2}$ keV with a $y$ of $2.99_{-0.18}^{+2.99}$ assuming a spherical geometry. We noticed excess emission from $\sim$10$-$35 keV arising due to Compton reflection and a broad Fe $K\alpha$ line at 6.43 keV with an equivalent width of 60 $\pm$ 5 eV. The variations in count rates in the soft (3$-$10 keV) band is found to be more compared to the hard (10$-$79 keV) band with mean fractional variability amplitudes of 0.065$\pm$0.002 and 0.052$\pm$0.003 for the soft and hard bands respectively. 3C 120 is known to have a strong jet, however, our results indicate that it is either dormant or its contribution if any to the X-ray emission is negligible during the epoch of ${\it NuSTAR}$ observation.