High Energy Flares of Blazars: The Case of
3C 279
Vaidehi S. Paliya
Indian Institute of Astrophysics
Introduction
• 3C 279 is a flat spectrum radio quasar (FSRQ) at z = 0.536
• It emits strong and variable radiation throughout the EM spectrum
• One of the first FSRQs to be detected by EGRET (Hartman+, 1992, ApJ, 385, L1)
• A subject of various MW campaigns since the launch of Fermi satellite
Image credit: NASA/DOE/Fermi LAT Collaboration
Introduction
• Multiple episodes of γ-ray flaring activities seen by Fermi
• Three of them (& a low state) are selected for a detailed study
✦ OB1: 2013 December; OB2: 2014 April; OB3: 2015 June
0 400 800 1200 1600 2000 2400
Time (MJD - 54600)
0 3 6
F0.1−300GeV(10−6 phcm−2 s−1 ) Low OB1 OB2 OB3
2009 2010 2011 2012 2013 2014 2015
0 3 6
F0.1−300GeV
Low
Flare 1 Flare 2
Fermi-LAT
0.4 0.6 0.8 1.0
F0.3−10keV Swift-XRT
3 6 9 FUV
SwiftW2 SwiftM2 SwiftW1
6 9 12 15
FOptical
SwiftU SwiftB SMARTS B SwiftV SMARTS V STEWARD V
15 30 45 60 FIR
SMARTS J SMARTS K
12 18 24
Pol.(%)
0 4 8 12 16 20
Time (MJD - 56640) 50
60 70
P.A.(degrees)
2013 December Flare
• The highest measured γ-ray flux is ~ 1.2 x 10-5 ph cm-2 s-1
• The shortest γ-ray and X-ray flux doubling times ~ 3 hrs
• Available observations suggest the uncorrelated variability
behavior
• This doesn’t support
conventional one-zone leptonic models
2013 December Flare
• An extremely hard γ-ray spectrum is observed
• Comparison of the shapes of the optical-UV and γ-ray
spectra provides another clue to the failure of one-zone
leptonic emission scenario
• Two independent approaches are adopted
• A two-zone leptonic emission (Paliya+, submitted)
1010 1012 1014 1016 1018 1020 1022 1024 1026 ν (Hz)
10−14 10−13 10−12 10−11 10−10 10−9 10−8
νFν(ergcm−2 s−1 )
Flare 1
Large blob inside BLR Small blob inside BLR
Tavecchio+, 2011, A&A, 534, 86
2013 December Flare
• An extremely hard γ-ray spectrum is observed
• Comparison of the shapes of the optical-UV and γ-ray
spectra provides another clue to the failure of one-zone
leptonic emission scenario
• Two independent approaches are adopted
• Lepto-hadronic processes
(Paliya+, submitted)
1011 1014 1017 1020 1023 1026
ν (Hz) 10−13
10−12 10−11 10−10 10−9
νFν(ergcm−2 s−1 )
Accretion disk
Electron/Positron synchrotron Flare 1
Muon synchrotron Proton synchrotron Equilibrium fit SSC
0 2 4 6 8
F0.1−300GeV Flare 1
Flare 2
Post−flare
One day binned
0.3 0.6 0.9
F0.3−10keV Swift-XRT PC mode
0.9 1.2 1.5 FUV
SwiftW2 SwiftM2 SwiftW1
1.6 2.0 2.4
FOptical
SwiftU SwiftB SMARTS B SwiftV SMARTS V STEWARD V
2 4 6 FIR
SMARTS J SMARTS K
9 12 15
Pol.(%)
0 4 8 12 16 20
Time (MJD - 56740) 40
50 60
P.A.(degrees)
2014 April Flare
• A bright γ-ray flare with amplitude similar to 2013 flare
• The shortest γ-ray variability time ~1 hr
• The flux enhancement is seen at all the wavelengths, thus supporting one-zone/co-
spatiality of the origin of the radiation
(Paliya+, 2015, ApJ, 803, 15)
108 1011 1014 1017 1020 1023 1026 ν (Hz)
10−14 10−13 10−12 10−11 10−10 10−9 10−8
νFν(ergcm−2 s−1 )
Flare 2
(MJD 56,749−56,755)
2014 April Flare
• At the peak of the flare, the γ- ray spectrum was curved
• The curvature is explained as a combination of EC-BLR &
EC-torus processes with Klein-Nishina mechanism playing a role
• The emission region was
located at the outer edge of the BLR
(Paliya+, 2015, ApJ, 803, 15)
2 4 6 8
F0.1−300GeV
0.3 0.6 0.9
F0.3−10keV
9 10 11 12 13 14 15
Time (MJD - 56740) 16
18 20 22 24
Γ
2014 April Flare
(Paliya+, 2015, ApJ, 803, 15)
1014 1016 1018 1020 1022 1024 1026 ν (Hz)
10−12 10−11 10−10 10−9
νFν(ergcm−2 s−1 )
Flare 2
(MJD 56,749−56,755) day 1
day 2 day 3 day 4 day 5 day 6
• The modeling of the fine time binned SEDs indicated the
increase in the bulk Lorentz factor as a primary cause of the flare
0 9 18 27 36
F0.1−300GeV
Pre
P1 P2
LAT Post
0.0 0.6 1.2 1.8
F0.3−10keV Swift-XRT
6 8 10 FUV
Swift W2 Swift M2 Swift W1
15 18 21
FOptical
Swift U
STEWARD R STEWARD V
18 24 30
Pol.(%)
0 2 4 6 8 10
Time (MJD - 57183)
20 30 40 50 60
P.A.(degrees)
2015 June Flare
• The brightest γ-ray flare ever detected from 3C 279
• The highest measured γ-ray flux is ~4 x 10-5 ph cm-2 s-1
• Similar to 2014 April flare, this event also showed
correlated variability
behavior across the EM spectrum
108 1011 1014 1017 1020 1023 1026 ν (Hz)
10−13 10−12 10−11 10−10 10−9 10−8
νFν(ergcm−2 s−1 )
P2
(MJD 57,189−57,190)
2015 June Flare
• A one-zone model successfully explains the observations
• The γ-ray spectrum showed a significant curvature similar to that seen in 2014 April flare
• The location of the emitting
region was again found to be at the outer edge of the BLR
(Paliya+, prep.)
1010 1013 1016 1019 1022 1025 ν (Hz)
10−14 10−13 10−12 10−11 10−10 10−9 10−8
νFν(ergcm−2 s−1 )
Low activity 2013 December 2014 April 2015 June
Summary
(Paliya+, prep.)
1010 1013 1016 1019 1022 1025 ν (Hz)
10−14 10−13 10−12 10−11 10−10 10−9 10−8
νFν(ergcm−2 s−1 )
Low activity 2013 December 2014 April 2015 June
Summary
• These three γ-ray flares
displayed the dominance of a
variety of the physical processes powering the jets of 3C 279
• The observations reflect the complexity involved in
understanding the radiative
mechanisms working in blazar jets
• A deep multi-wavelength
monitoring may reveal similar
features from other blazars also (Paliya+, prep.)
