Coronal Proerties of the Seyfert 1 Galaxy 3C 120 with NuSTAR

Abstract

We present a 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 ~120 ks of observation from NuSTAR. The quality broadband spectrum from 3–79 keV 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, compPS, to the observed broadband spectrum, we derived the kinetic temperature of the electrons in the corona to be kT e = 25 ± 2 keV with a Compton y parameter of y = 2.2 ± 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 ~10–35 keV arising due to Compton reflection and a broad Fe Kα line at 6.43 keV with an equivalent width of 60 ± 5 eV. The variations in count rates in the soft (3–10 keV) band are found to be larger compared to the hard (10–79 keV) band, with mean fractional variability amplitudes of 0.065 ± 0.002 and 0.052 ± 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 NuSTAR observation.