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First NuSTAR observations of the BL Lac-type blazar PKS~2155-304: constraints on the jet content and distribution of radiating particles

Madejski, G. M. and Madsen, K. K. and Baloković, M. and Harrison, F. A. and Forster, K. and Grefenstette, B. and Mao, P. H. and Miyasaka, H. and Rana, V. (2016) First NuSTAR observations of the BL Lac-type blazar PKS~2155-304: constraints on the jet content and distribution of radiating particles. Astrophysical Journal, 831 (2). Art. No. 142. ISSN 0004-637X. doi:10.3847/0004-637X/831/2/142.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Madsen, K. K.0000-0003-1252-4891
Baloković, M.0000-0003-0476-6647
Harrison, F. A.0000-0003-2992-8024
Forster, K.0000-0001-5800-5531
Grefenstette, B.0000-0002-1984-2932
Miyasaka, H.0000-0002-8074-4186
Rana, V.0000-0003-1703-8796
Additional Information:© 2016 American Astronomical Society. Received 2016 August 2; revised 2016 August 25; accepted 2016 August 29; published 2016 November 3. The Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (United States), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A. Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowledged. This work was partially supported under the NASA contract No. NNG08FD60C, and made use of observations from the NuSTAR mission, a project led by California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA. We thank the NuSTAR Operations, Software, and Calibration teams for support in the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). K.N. was supported by NASA through Einstein Postdoctoral Fellowship grant number PF3-140130 awarded by the Chandra X-ray Center, and by the Polish National Science Centre grant 2015/18/E/ST9/00580. M.B. acknowledges support from NASA under the NASA Earth and Space Science Fellowship Program, grant NNX14AQ07H.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
Commissariat à l’Energie Atomique (CEA)UNSPECIFIED
Institut National de Physique Nucléaire et de Physique des Particules (IN2P3)UNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Swedish Research CouncilUNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
NASA Einstein FellowshipPF3-140130
National Science Centre (Poland)2015/18/E/ST9/00580
NASA Earth and Space Science FellowshipNNX14AQ07H
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut de recherche sur les lois fondamentales de l'Univers (Irfu)UNSPECIFIED
Swedish National Space Board (SNSB)UNSPECIFIED
Subject Keywords:BL Lacertae objects: individual (PKS 2155-304) ; galaxies: active; galaxies: jets; gamma rays: galaxies; radiation mechanisms: non-thermal
Issue or Number:2
Record Number:CaltechAUTHORS:20161104-080424476
Persistent URL:
Official Citation:G. M. Madejski et al 2016 ApJ 831 142
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71731
Deposited By: Ruth Sustaita
Deposited On:04 Nov 2016 16:27
Last Modified:11 Nov 2021 04:50

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