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

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 $\sim$0.1 keV, similar to low-luminosity, non-jetted Seyferts. Here we present the analysis of the simultaneous XMM-Newton and NuSTAR observation of the luminous FSRQ 4C+25.05 ($z=2.368$). The observed 0.3-30 keV spectrum is best described by the sum of a hard X-ray power law ($\Gamma =1.38_{-0.03}^{+0.05}$) and a soft component, approximated by a blackbody with $k{T}_{\mathrm{BB}}=0.66_{-0.04}^{+0.05}$ 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 ${\Gamma }_{\mathrm{bulk}}\sim 11.7$. 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.

arXiv comment6 pages, 4 figures, 2 tables. Accepted for publication in MNRASL

References in corpus (31)

• Unified Schemes for Radio-Loud Active Galactic Nuclei
• On the Absorption of X-rays in the Interstellar Medium
• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Overview and Early Data
• The XMM-Newton view of PG quasars I. X-ray continuum and absorption
• The power of blazar jets
• Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes
• Calibration of the NuSTAR High Energy Focusing X-ray Telescope
• An X-ray Spectral Survey of Radio-Loud AGN With ASCA
• Normalizing a Relativistic Model of X-ray Reflection: The Definition of the Reflection Fraction and its Implementation in relxill
• Keck High Resolution Spectroscopy of PKS 0123+257: Intrinsic Absorption in a Radio Loud Quasar
• The spectrum of the Broad Line Region and the high-energy emission of powerful blazars
• Multiwavelength Observations of the Powerful Gamma-ray Quasar PKS 1510-089: Clues on the Jet Composition
• Compton rockets and the minimum power of relativistic jets
• Bulk Comptonization spectra in blazars
• Determining the Fraction of Intrinsic CIV Absorption in Quasi-Stellar Object Absorption Line Systems
• On the July 2007 flare of the blazar 3C 454.3
• Associated absorption in radio quasars. I. C IV absorption and the growth of radio sources
• Virial Masses of Black Holes from Single Epoch Spectra of AGN
• The jet/disk connection in AGN: Chandra and XMM observations of three powerful radio-loud quasars
• The blazar GB1428+4217: a warm absorber at z=4.72?
• Broadband Observations of High Redshift Blazars
• Intrinsic Absorption in Radio-Selected QSOs
• AGN Coronae Through A Jet Perspective
• The ASCA spectrum of the z=4.72 blazar, GB 1428+4217
• ROSAT PSPC detection of soft X-ray absorption in GB 1428+4217: The most distant matter yet probed with X-ray spectroscopy
• X-ray Absorption of High Redshift Quasars
• Radio and X-ray observations of an exceptional radio flare in the extreme z=4.72 blazar GB B1428+4217
• XMM-Newton discovery of soft X-ray absorption in the high-z superluminous Blazar RBS 315

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