NuStar View of the Central Region of the Perseus Cluster

Abstract

Located at the center of the Perseus cluster, 3C 84 is an extremely bright and nearby radio galaxy. Because of the strong diffuse thermal emission from the cluster in X-rays, the detailed properties and the origin of a power-law component from the central active galactic nucleus (AGN) remains unclear in the source. We report here the first NuSTAR observations of 3C 84. The source was observed for 24.2 and 32 ks on February 01 and 04, 2018, respectively. NuSTAR observations spectrally decompose the power-law AGN component above 10 keV. The power-law component dominates the spectrum above 20 keV with a photon index ∼1.9 and an energy flux F 20−30 keV = 1.0 ×10 −11 erg cm −2 s −1 , corresponding to an isotropic luminosity, L 20−30 keV = 7.4×10 42 erg s −1 . We discuss possible emitting sites for the power-law component. The expected thermal emission from the accretion disk is not hot enough to account for the hard X-rays detected from the source. Similar X-ray and γ-ray photon indices and long-term flux variations, the absence of cutoff energy in the hard X-ray spectrum of the source, correlated hard X-ray flux and hardness ratio variations, and the similarity of optical-X-ray slope to blazar rather than Seyfert galaxies supports the hard X-ray power-law component originating from the jet.

X-ray and Gamma-ray Variability of NGC 1275

“…This accounts for the variation in constant factor between observations. In addition, the spectral parameters obtained here are consistent with the ones reported by [12] using NuSTAR data alone for 1 February 2017 and 4 February 2017.…”

“…Line of sight absorption was modelled with tbabs. A similar spectral model was used by [26] to model the large scale temperature structure of the Perseus cluster using Suzaku data and later by [12] to model NuSTAR data. In the present work, a much wider energy range obtained by combining XRT and NuSTAR data is used.…”

“…Powerlaw indices obtained here are consistent with the values of 1.52 ± 0.08 (25 February 2016), 1.75 ± 0.12 (30 December 2016) and 1.77 ± 0.17 (1 January 2017) reported by [32] based on XRT data alone. Rani et al [12] have reported powerlaw indices of 1.85 −0.14 +0.12 and 1.90 −0.13 +0.11 based on NuSTAR data alone for 1 February 2017 and 4 February 2017 respectively. Figure 7 shows the multiwaveband SED for the three observations by XRT-NuSTAR along with the quasi-simultaneous spectral measurements from Fermi-LAT.…”

“…Swift-BAT observations though could not resolve the nucleus spatially, excess hard X-ray emission was inferred over and above the thermal emission with a photon index of 1.7 ± 0.3 and a flux of 10 −11 erg cm −2 s −1 (15-55 keV) [11]. More recently, NuSTAR data in hard X-ray band were analysed by [12]. They studied the power-law component which dominates above 20 keV.…”

A New Chapter in Hard X-rays of the M87 AGN

“…Thus, we argue that the X-ray spectrum is more consistent with a jet origin, although emission from the ADAF cannot be completely ruled out. It is interesting that in another nearby radio galaxy, 3C 84, no cut-off in the power-law spectrum was found, and the hard X-ray emission is also more consistent with a jet origin [17]. The jet origin of the M87 core is also supported by Faraday rotation measure observations [18,19].…”