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

TL;DR

This study measures the coronal temperature of Seyfert galaxy 3C 120 using NuSTAR data, revealing a plasma temperature around 25-26 keV, and finds that jet contribution to X-ray emission is negligible during observation.

Contribution

First measurement of the coronal electron temperature in 3C 120 using NuSTAR broad band spectrum with advanced Comptonization models.

Findings

Coronal electron temperature is approximately 25-26 keV.

Detected broad Fe Kα line at 6.43 keV.

Soft X-ray variability exceeds hard X-ray variability.

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.