J/ApJ/657/706 EGRET blazar gamma-ray spectrum (Nandikotkur+, 2007)
Does the blazar gamma-ray spectrum harden with increasing flux ?
Analysis of 9 years of EGRET data.
Nandikotkur G., Jahoda K.M., Hartman R.C., Mukherjee R., Sreekumar P.,
Bottcher M., Sambruna R.M., Swank J.H.
<Astrophys. J., 657, 706-724 (2007)>
=2007ApJ...657..706N 2007ApJ...657..706N
ADC_Keywords: QSOs ; BL Lac objects ; Gamma rays
Keywords: galaxies: active - methods: data analysis - methods: statistical -
radiation mechanisms: nonthermal
Abstract:
The Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton
Gamma-Ray Observatory (CGRO) discovered gamma-ray emission from more
than 67 blazars during its 9yr lifetime. We conducted an exhaustive
search of the EGRET archives and selected all the blazars that were
observed multiple times and were bright enough to enable a spectral
analysis using standard power-law models. The sample consists of 18
flat-spectrum radio quasars (FSRQs), 6 low-frequency peaked BL Lac
objects (LBLs) and 2 high-frequency peaked BL Lac objects (HBLs). We
do not detect any clear pattern in the variation of spectral index
with flux. Some of the blazars do not show any statistical evidence
for spectral variability.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 93 98 Photon Spectral index (30MeV-10GeV), average flux
(>100MeV) and Log(synchrotron peak frequency) of
blazars detected by EGRET
table3.dat 111 151 Gamma-ray photon spectral index (30MeV-10GeV) and
flux (>100MeV) of blazars that were bright and
were observed multiple times by EGRET
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See also:
J/ApJS/123/79 : Third EGRET catalog (3EG) (Hartman+, 1999)
J/A+A/489/849 : Revised catalogue of EGRET gamma-ray sources (Casandjian+ 2008)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Source name (HHMM+DDd or HHMM+DDMM)
QSO BHHMM+DDd in Simbad
11 A1 --- n_Name [*] 0804+499 also named 0809+483
13 A1 --- u_Name [?] Possible EGRET identification?
15- 34 A20 --- OName Other name
36- 41 F6.2 deg RAdeg Right Ascension decimal degrees (J2000) (2)
43- 48 F6.2 deg DEdeg Declination in decimal degrees (J2000) (2)
50- 53 F4.2 --- alpha ? Spectral index (G1)
55- 58 F4.2 --- e_alpha ? Uncertainty in alpha
60 A1 --- f_alpha [e] alpha during a flare (4)
62- 66 F5.2 10-4/m2/s Flux Average flux at >100MeV (G2)
68- 71 F4.1 10-4/m2/s e_Flux Uncertainty in Flux (G2)
73- 76 F4.1 [Hz] lognu ? Log of the synchrotron peak frequency (6)
78- 80 F3.1 [Hz] e_lognu ? Uncertainty in lognu
82 A1 --- M [Y/N] Multiple observations? (7)
84- 93 A10 --- Class Classification (8)
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Note (2): These are EGRET positions from the 3rd EGRET catalog
(Hartman et al., 1999, Cat. J/ApJS/123/79, 3EG).
Note (4): 'e' = Spectral index is during a flare. This was the only
spectral index that could be calculated. The quoted flux is the
average flux observed
Note (6): These have been obtained from the literature cited in Section 4.1.
Note (7): Here the Y/N indicate the following:
Y = Observed multiple times and were bright enough during those
observations to yield a spectral index
N = not observed multiple times
Note (8): Based on Hartman et al. (1997, AIP Conf. Proc. 410, 307) and
Ghisellini et al. (1998MNRAS.301..451G 1998MNRAS.301..451G):
FSRQ = flat-spectrum radio quasar
LBL = low-frequency peaked BL Lacs
HBL = high-frequency peaked BL Lacs
FSRS = flat-spectrum radio source
HP = high-polarization
LP = low-polarization
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Source name (HHMM+DDd or HHMM+DDMM)
QSO BHHMM+DDd in Simbad (1)
11- 19 A9 --- OName Other name
22- 50 A29 --- Dates Start date(s)
52- 71 A20 --- Period Viewing periods pooled
73- 79 A7 --- Fig3 Graph label in Figure 3 (2)
81 A1 --- f_Fig3 [b] Fraction of the viewing period (3)
83- 86 F4.2 --- alpha ? Spectral Index (G1)
88- 91 F4.2 --- e_alpha ? Uncertainty in alpha
93- 99 F7.3 10-4/m2/s Flux ? Mean flux at >100MeV (G2)
101-105 F5.2 10-4/m2/s e_Flux ? Uncertainty in Flux (G2)
107-111 F5.2 --- sigma ? Detection significance
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Note (1): In original file, 0827+343 is a misprint for 0827+243 and
0917+499 is a misprint for 0917+449.
Note (2): The label used to identify each point in the spectral index vs.
flux plots shown in Fig. 3. The labels are represented by a decimal
number if the data is from a single viewing period, and an integer
if the data from one ore more EGRET Cycle(s) is combined.
Note (3): 'b' indicates a combination of only a fraction of the viewing
periods during a cycle. The source was comparatively faint during the
other viewing periods of the cycle
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Global notes:
Note (G1): Photon index measured in the 30MeV-10GeV energy range,
with F(E)∝E-α
Note (G2): In units of 10-8 photons/cm2/s.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 08-Jan-2009