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Bulk Comptonization: new hints from the luminous blazar 4C+25.05

Kammoun, E. S. and Nardini, E. and Risaliti, G. and Ghisellini, G. and Behar, E. and Celotti, A. (2018) Bulk Comptonization: new hints from the luminous blazar 4C+25.05. Monthly Notices of the Royal Astronomical Society: Letters, 473 (1). L89-L93. ISSN 1745-3933. http://resolver.caltech.edu/CaltechAUTHORS:20171006-100333383

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Abstract

Blazars are often characterized by a spectral break at soft X-rays, whose origin is still debated. While most sources show a flattening, some exhibit a blackbody-like soft excess with temperatures of the order of ∼0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here, we present the analysis of the simultaneous XMM–Newton and NuSTAR observations of the luminous flat-spectrum radio quasar 4C+25.05 (z = 2.368). The observed 0.3–30 keV spectrum is best described by the sum of a hard X-ray power law (Γ=1.38^(+0.05)_(−0.03)) and a soft component, approximated by a blackbody with kT_(BB)=0.66^(+0.05)_(−0.04) keV (rest frame). If the spectrum of 4C+25.05 is interpreted in the context of bulk Comptonization by cold electrons of broad-line region photons emitted in the direction of the jet, such an unusual temperature implies a bulk Lorentz factor of the jet of Γ_(bulk) ∼ 11.7. Bulk Comptonization is expected to be ubiquitous on physical grounds, yet no clear signature of it has been found so far, possibly due to its transient nature and the lack of high-quality, broad-band X-ray spectra.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1093/mnrasl/slx164DOIArticle
https://academic.oup.com/mnrasl/article/473/1/L89/4349750PublisherArticle
http://arxiv.org/abs/1710.01748arXivDiscussion Paper
Additional Information:© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 October 3. Received 2017 October 2; in original form 2017 September 9. Published: 05 October 2017. EN is supported by the EU through the Horizon 2020 Marie Skłodowska-Curie grant agreement no. 664931. EB is supported by the EU through the Horizon 2020 Marie Skłodowska-Curie grant agreement no. 655324. The results presented in this letter are based on data obtained with the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA; XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS), jointly developed by the ASI Science Data Center (Italy) and the California Institute of Technology (USA). The figures were generated using matplotlib (Hunter 2007), a PYTHON library for publication of quality graphics. The MCMC results were presented using the open source code corner.py (Foreman-Mackey 2016).
Group:NuSTAR
Subject Keywords:galaxies: active – quasars: general – quasars: individual: 4C+25.05 –X-rays: galaxies –X-rays: general
Record Number:10.1093/mnrasl/slx164
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171006-100333383
Official Citation:E. S. Kammoun, E. Nardini, G. Risaliti, G. Ghisellini, E. Behar, A. Celotti; Bulk Comptonization: new hints from the luminous blazar 4C+25.05, Monthly Notices of the Royal Astronomical Society: Letters, Volume 473, Issue 1, 1 January 2018, Pages L89–L93, https://doi.org/10.1093/mnrasl/slx164
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:82157
Collection:CaltechAUTHORS
Deposited By: Joy Painter
Deposited On:06 Oct 2017 17:11
Last Modified:05 Feb 2018 20:49

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