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The Origins of the Gamma-Ray Flux Variations of NGC 1275 Based on Eight Years of Fermi-LAT Observations

Journal Article · · The Astrophysical Journal (Online)
 [1];  [1];  [2];  [1];  [3];  [4];  [5]
  1. Waseda Univ., Tokyo (Japan)
  2. Waseda Univ., Tokyo (Japan); Kanazawa Univ., Ishikawa (Japan)
  3. Naval Research Lab., Washington D.C. (United States)
  4. Stanford Univ., Stanford, CA (United States)
  5. Hiroshima Univ., Hiroshima (Japan)
+ Show Author Affiliations
Here, we present an analysis of eight years of Fermi-LAT (>0.1 GeV) γ-ray data obtained for the radio galaxy NGC 1275. The γ-ray flux from NGC 1275 is highly variable on short (~days to weeks) timescales, and has steadily increased over this eight year timespan. By examining the changes in its flux and spectral shape in the LAT energy band over the entire data set, we found that its spectral behavior changed around 2011 February (~MJD 55600). The γ-ray spectra at early times evolved largely at high energies, while the photon indices were unchanged at later times despite rather large flux variations. To explain these observations, we suggest that the flux changes at the early times were caused by injection of high-energy electrons into the jet while, later, the γ-ray flares were caused by a changing Doppler factor owing to variations in the jet Lorentz factor and/or changes in the angle to our line of sight. To demonstrate the viability of these scenarios, we fit the broad band spectral energy distribution data with a one-zone synchrotron self-Compton (SSC) model for flaring and quiescent intervals before and after 2011 February. To explain the γ-ray spectral behavior in the context of the SSC model, the maximum electron Lorentz factor would have changed at the early times, while a modest change in the Doppler factor adequately fits the quiescent and flaring state γ-ray spectra at the later times.
Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1460993
Journal Information:
The Astrophysical Journal (Online), Journal Name: The Astrophysical Journal (Online) Journal Issue: 1 Vol. 860; ISSN 1538-4357
Publisher:
Institute of Physics (IOP)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (9)

Gamma-ray observations of low-luminosity active galactic nuclei journal January 2020
Faint γ-ray sources at low redshift: the radio galaxy IC 1531 journal September 2018
Intra-night optical variability of misaligned active galaxies journal December 2018
3C 84: Observational Evidence for Precession and a Possible Relation to TeV Emission journal August 2019
Two Blobs in a Jet Model for the γ -Ray Emission in Radio Galaxies journal September 2018
Inverse Compton Scattering of Starlight in the Kiloparsec-scale Jet in Centaurus A: The Origin of Excess TeV γ -Ray Emission journal June 2019
Analysis of the Spatially Resolved V −3.6 μ m Colors and Dust Extinction in 257 Nearby NGC and IC Galaxies journal October 2019
NuStar View of the Central Region of the Perseus Cluster journal October 2018
Gamma-ray observations of low-luminosity active galactic nuclei text January 2020

Figures / Tables (12)

Figure 1(p. 4)figure Figure 1
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Table 1(p. 6)table Table 1
Figure 4(p. 7)figure Figure 4
Figure 5(p. 7)figure Figure 5
Table 2(p. 7)table Table 2
Figure 6(p. 8)figure Figure 6
Figure 7(p. 8)figure Figure 7
Figure 8(p. 8)figure Figure 8
Figure 9(p. 11)figure Figure 9
Table 3(p. 11)table Table 3

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
galaxies: Seyfert
galaxies: active
galaxies: individual (NGC 1275)
galaxies: jets
gamma rays: general
radiation mechanisms: non-thermal