Open AccessExploring High-energy Emission from the BL Lacertae Object S5 0716+714 with the Fermi Large Area Telescope
Author(s) -
Xiongfei Geng,
W. Zeng,
Bindu Rani,
R. J. Britto,
Guomei Zhang,
T. Wen,
Wen Hu,
Stefan Larsson,
D. J. Thompson,
S. B. Yang,
Guojie Cao,
B. Z. Dai
Publication year - 2020
Publication title -
astrophysical journal/the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.3847/1538-4357/abb603
Subject(s) - physics , astrophysics , bl lac object , light curve , blazar , fermi gamma ray space telescope , spectral energy distribution , flux (metallurgy) , telescope , astronomy , galaxy , gamma ray , materials science , metallurgy
We present the results of an extensive γ -ray data analysis of the emission from the blazar S5 0716+714 with the primary motivation to study its temporal and spectral variability behavior. In this work, we extract a 10 days binned γ -ray light curve from 2008 August 4 to 2016 April 27 in the energy range of 0.1–300 GeV and identify six outburst periods with peak flux of >4 × 10 −7 ph cm −2 s −1 from this highly variable source. The brightest flares are identified by zooming in these outburst periods to 1 day binning and using the Bayesian Blocks algorithm. The fastest variability timescale is found to be 1.5 ± 0.3 hr at MJD 57128.01 ± 0.01 with a peak flux above 100 MeV of (26.8 ± 6.9) × 10 −7 ph cm −2 s −1 . No hint of periodic modulations has been detected for the light curve of S5 0716+714. During the outburst phases, the γ -ray spectrum shows an obvious spectral break with a break energy between 0.93 and 6.90 GeV energies, which may be caused by an intrinsic break in the energy distribution of radiating particles. The five highest-energy photons, with E > 100 GeV, imply that the high-energy emission from this source may originate from a moving emission region in a helical path upstream in the jet. The spectral behavior and temporal characteristics of the individual flares indicate that the location of the emission region lies in the sub-parsec scale ( r γ < 0.85 pc).