NuSTARREVEALS THE COMPTONIZING CORONA OF THE BROAD-LINE RADIO GALAXY 3C 382

Abstract

Broad-line radio galaxies (BLRGs) are active galactic nuclei that produce powerful, large-scale radio jets, but appear as Seyfert 1 galaxies in their optical spectra. In the X-ray band, BLRGs also appear like Seyfert galaxies, but with flatter spectra and weaker reflection features. One explanation for these properties is that the X-ray continuum is diluted by emission from the jet. Here, we present two NuSTAR observations of the BLRG 3C 382 that show clear evidence that the continuum of this source is dominated by thermal Comptonization, as in Seyfert 1 galaxies. The two observations were separated by over a year and found 3C 382 in different states separated by a factor of 1.7 in flux. The lower flux spectrum has a photon-index of Γ = 1.68 +0.03 −0.02 , while the photon-index of the higher flux spectrum is Γ = 1.78 +0.02 −0.03 . Thermal and anisotropic Comptonization models provide an excellent fit to both spectra and show that the coronal plasma cooled from kT e = 330 ± 30 keV in the low flux data to 231 +50 −88 keV in the high flux observation. This cooling behavior is typical of Comptonizing corona in Seyfert galaxies and is distinct from the variations observed in jet-dominated sources. In the high flux observation, simultaneous Swift data are leveraged to obtain a broadband spectral energy distribution and indicates that the corona intercepts ∼ 10% of the optical and ultraviolet emitting accretion disk. 3C 382 exhibits very weak reflection features, with no detectable relativistic Fe Kα line, that may be best explained by an outflowing corona combined with an ionized inner accretion disk.

CORONAL PROPERTIES OF THE SEYFERT 1.9 GALAXY MCG-05-23-016 DETERMINED FROM HARD X-RAY SPECTROSCOPY WITHNuSTAR

“…Systematics are clearly less of an issue with lower-quality data, as demonstrated by the calibration observation data presented here: in that case the constraints on spectral parameters are weakened, and the systematic uncertainty gets absorbed in the statistical uncertainty. This has been the case for the majority of the similar measurements on other AGNs published so far, including the recent ones based on the NuSTAR data (Brenneman et al 2014a;Marinucci et al 2014;Ballantyne et al 2014). As in the case of IC 4329a (Brenneman et al 2014b), additional constraints come from joint analyses of simultaneous soft and hard X-ray data sets, leading to further improvement in constraining E cut .…”

“…Using the NuSTAR data, the cut-off energies have recently been measured for IC 4329a (E cut = 184 ± 14 keV; Brenneman et al 2014b), SWIFT J2127.4 + 5654 (E cut = 108 +11 −10 keV; Marinucci et al 2014) and 3C 382 (E cut = 214 +147 −63 and >190 keV in two distinct spectral states; Ballantyne et al 2014). The high quality of the NuSTAR spectra in the hard X-ray band up to 79 keV enable reliable independent measurements of the physical parameters of the corona: its temperature, kT e , and optical depth, τ e .…”

A Long Look at MCG-5-23-16 with NuSTAR. I. Relativistic Reflection and Coronal Properties

“…As we pointed out in Section 4.2.1, results from AGNs are not yet conclusive, where both a correlation and an anti-correlation of E c and flux have been reported for 3C382 and Mrk335, respectively (Ballantyne et al 2014;Keek & Ballantyne 2016).…”

“…The uncertainties in the parameters are, however, large. Using NuSTAR, Ballantyne et al (2014) analyzed two observations of the radio galaxy 3C382 in two flux intervals. The low flux observation had a flatter spectrum and a higher cutoff energy compared to the higher flux observation (i.e., opposite the trend seen in INTEGRAL data and seen here in MCG-5-23-16 ).…”

“…With its effective area and continuous energy coverage that includes the iron line at 6 keV and the Compton hump peaking at ∼30 keV, NuSTAR provides a better handle on obtaining accurate estimates (or stringent limits) of the Comptonization parameters. Many estimates have been published so far for individual Seyfert and radio galaxies, including IC 4329A , Ark 120 (Matt et al 2014), MCG-6-30-15 (Marinucci et al 2014b), SWIFT J2127.4+5654 (Marinucci et al 2014a), NGC4945 (Puccetti et al 2014), MCG-5-23-16 (Baloković et al 2015), NGC 2110 , NGC5506 , NGC4151 (Keck et al 2015), NGC7213 (Ursini et al 2015b), 3C273 (Madsen et al 2015a), NGC5548 (Ursini et al 2015a), 3C390.3 , 3C382 (Ballantyne et al 2014), and Mrk 335 (Wilkins et al 2015;Keek & Ballantyne 2016). Cutoff energies in the range 100-500 keV are measured, and although these values are outside the energy band of NuSTAR (3-79 keV), the fact that the spectra starts rolling over well below the cutoff energyand the effect of the cutoff on the reflection spectrum, which cannot be mimicked by other parameters, allows accurate measurements of the cutoff energy (García et al 2015).…”