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Title: Curvature of the spectral energy distributions of blazars

Abstract

In this paper, spectral energy distributions (SED) of both synchrotron and inverse Compton (IC) components of a sample of Fermi bright blazars are fitted by a log-parabolic law. The second-degree term of the log parabola measures the curvature of an SED. We find a statistically significant correlation between the synchrotron peak frequency and its curvature. This result is in agreement with the theoretical prediction and confirms previous studies that dealt with a single source with observations at various epochs or a small sample. If a broken power law is employed to fit the SED, the difference between the two spectral indices (i.e., |α{sub 2} – α{sub 1}|) can be considered a 'surrogate' of the SED curvature. We collect data from the literature and find a correlation between the synchrotron peak frequency and the spectral difference. We do not find a significant correlation between the IC peak frequency and its curvature, which may be caused by a complicated seed photon field. It is also found that the synchrotron curvatures are on average larger than those of IC curvatures, and there is no correlation between these two parameters. As suggested by previous works, both the log-parabolic law of the SED and themore » above correlation can be explained by statistical and/or stochastic particle accelerations. Based on a comparison of the slops of the correlation, our result seems to favor stochastic acceleration mechanisms and emission processes. Additional evidence, including SED modeling, particle acceleration simulation, and comparisons between some predictions and empirical relations/correlations, also seems to support the idea that the electron energy distribution (and/or synchrotron SED) may be log-parabolic.« less

Authors:
 [1]
  1. Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, ChinaAND (China)
Publication Date:
OSTI Identifier:
22356560
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; BL LACERTAE OBJECTS; COMPARATIVE EVALUATIONS; CORRELATIONS; ELECTRONS; EMISSION; ENERGY SPECTRA; GALAXIES; SIMULATION; SYNCHROTRONS

Citation Formats

Chen, Liang, and Key Laboratory of Modern Astronomy and Astrophysics. Curvature of the spectral energy distributions of blazars. United States: N. p., 2014. Web. doi:10.1088/0004-637X/788/2/179.
Chen, Liang, & Key Laboratory of Modern Astronomy and Astrophysics. Curvature of the spectral energy distributions of blazars. United States. https://doi.org/10.1088/0004-637X/788/2/179
Chen, Liang, and Key Laboratory of Modern Astronomy and Astrophysics. 2014. "Curvature of the spectral energy distributions of blazars". United States. https://doi.org/10.1088/0004-637X/788/2/179.
@article{osti_22356560,
title = {Curvature of the spectral energy distributions of blazars},
author = {Chen, Liang and Key Laboratory of Modern Astronomy and Astrophysics},
abstractNote = {In this paper, spectral energy distributions (SED) of both synchrotron and inverse Compton (IC) components of a sample of Fermi bright blazars are fitted by a log-parabolic law. The second-degree term of the log parabola measures the curvature of an SED. We find a statistically significant correlation between the synchrotron peak frequency and its curvature. This result is in agreement with the theoretical prediction and confirms previous studies that dealt with a single source with observations at various epochs or a small sample. If a broken power law is employed to fit the SED, the difference between the two spectral indices (i.e., |α{sub 2} – α{sub 1}|) can be considered a 'surrogate' of the SED curvature. We collect data from the literature and find a correlation between the synchrotron peak frequency and the spectral difference. We do not find a significant correlation between the IC peak frequency and its curvature, which may be caused by a complicated seed photon field. It is also found that the synchrotron curvatures are on average larger than those of IC curvatures, and there is no correlation between these two parameters. As suggested by previous works, both the log-parabolic law of the SED and the above correlation can be explained by statistical and/or stochastic particle accelerations. Based on a comparison of the slops of the correlation, our result seems to favor stochastic acceleration mechanisms and emission processes. Additional evidence, including SED modeling, particle acceleration simulation, and comparisons between some predictions and empirical relations/correlations, also seems to support the idea that the electron energy distribution (and/or synchrotron SED) may be log-parabolic.},
doi = {10.1088/0004-637X/788/2/179},
url = {https://www.osti.gov/biblio/22356560}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 788,
place = {United States},
year = {Fri Jun 20 00:00:00 EDT 2014},
month = {Fri Jun 20 00:00:00 EDT 2014}
}