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http://hdl.handle.net/20.500.12386/30209
Title: | First NuSTAR Observations of the BL Lac-type Blazar PKS 2155-304: Constraints on the Jet Content and Distribution of Radiating Particles | Authors: | Madejski, G. M. Nalewajko, K. Madsen, K. K. Chiang, J. Baloković, M. Paneque, D. Furniss, A. K. Hayashida, M. Urry, C. M. Sikora, M. Ajello, M. Blandford, R. D. Harrison, F. A. Sanchez, D. Giebels, B. Stern, D. Alexander, D. M. Barret, D. Boggs, S. E. Christensen, F. E. Craig, W. W. Forster, K. Giommi, P. Grefenstette, B. Hailey, C. Hornstrup, A. Kitaguchi, T. Koglin, J. E. Mao, P. H. Miyasaka, H. Mori, K. PERRI, Matteo Pivovaroff, M. J. Puccetti, S. Rana, V. Westergaard, N. J. Zhang, W. W. Zoglauer, A. |
Issue Date: | 2016 | Journal: | THE ASTROPHYSICAL JOURNAL | Number: | 831 | Issue: | 2 | First Page: | 142 | Abstract: | We report the first hard X-ray observations with NuSTAR of the BL Lac-type blazar PKS 2155-304, augmented with soft X-ray data from XMM-Newton and γ-ray data from the Fermi Large Area Telescope, obtained in 2013 April when the source was in a very low flux state. A joint NuSTAR and XMM spectrum, covering the energy range 0.5-60 keV, is best described by a model consisting of a log-parabola component with curvature β = 0.3(-0.1,+0.2) and a (local) photon index 3.04 ± 0.15 at photon energy of 2 keV, and a hard power-law tail with photon index 2.2 ± 0.4. The hard X-ray tail can be smoothly joined to the quasi-simultaneous γ-ray spectrum by a synchrotron self-Compton component produced by an electron distribution with index p = 2.2. Assuming that the power-law electron distribution extends down to γ_min = 1 and that there is one proton per electron, an unrealistically high total jet power of L_p ∼ 10^47 erg s^-1 is inferred. This can be reduced by two orders of magnitude either by considering a significant presence of electron-positron pairs with lepton-to-proton ratio n_e+_e-/n_p ∼ 30, or by introducing an additional, low-energy break in the electron energy distribution at the electron Lorentz factor γ_br1 ∼ 100. In either case, the jet composition is expected to be strongly matter-dominated. | URI: | http://hdl.handle.net/20.500.12386/30209 | URL: | https://iopscience.iop.org/article/10.3847/0004-637X/831/2/142 | ISSN: | 0004-637X | DOI: | 10.3847/0004-637X/831/2/142 | Bibcode ADS: | 2016ApJ...831..142M | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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