2007ApJ...657..706N

Query : 2007ApJ...657..706N

2007ApJ...657..706N - Astrophys. J., 657, 706-724 (2007/March-2)

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. and SWANK J.H.

Abstract (from CDS):

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 9 yr 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. The spectrum hardens with increasing flux in a few cases. There is also evidence for a flux-hardness anticorrelation at low fluxes in five blazars. The well-observed blazars (3C 279, 3C 273, PKS 0528+134, PKS 1622-297, PKS 0208-512) do not show any overall trend in the long-term spectral dependence on flux, but the sample shows a mixture of hard and soft states. We observed a previously unreported spectral hysteresis at weekly timescales in all three FSRQs for which data from flares lasting for ~(3-4) weeks were available. All three sources show a counterclockwise rotation, despite the widely different flux profiles. We analyze the observed spectral behavior in the context of various inverse Compton mechanisms believed to be responsible for emission in the EGRET energy range. Our analysis uses the EGRET skymaps that were regenerated to include the changes in performance during the mission.

Abstract Copyright: ∼

Journal keyword(s): Galaxies: Active - Methods: Data Analysis - Methods: Statistical - Radiation Mechanisms: Nonthermal

VizieR on-line data: <Available at CDS (J/ApJ/657/706): table2.dat table3.dat>

CDS comments: In table3, 0827+343 is a misprint for 0827+243 and 0917+499 is a misprint for 0917+449

Simbad objects: 84

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Number of rows : 84
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 QSO B0119+041 Bla 01 21 56.86169274 +04 22 24.7342932   19.2 19.5 19.40   ~ 200 1
2 QSO B0130-17 Bla 01 32 43.48746292 -16 54 48.5220804   18.75 18.44 15.44   ~ 247 1
3 4C 15.05 Bla 02 04 50.41389294 +15 14 11.0436097   21.9 21.00 21.00   ~ 426 1
4 QSO B0208-512 BLL 02 10 46.2004407600 -51 01 01.893013392   17.10 16.93 14.82   ~ 485 1
5 3C 66A BLL 02 22 39.6114771888 +43 02 07.799534304   15.71 15.21 14.5   ~ 942 2
6 4C 28.07 Bla 02 37 52.40567519 +28 48 08.9899986     19.30 16.99   ~ 654 1
7 QSO B0235+1624 BLL 02 38 38.93010450 +16 36 59.2745528   16.46 15.50 15.92   ~ 1614 2
8 QSO B0336-0156 Bla 03 39 30.93778633 -01 46 35.8041892   18.96 18.41 17.33   ~ 598 1
9 QSO B0414-189 Bla 04 16 36.54444889 -18 51 08.3402457   18.89 18.0 18.51   ~ 195 1
10 3C 111 Sy1 04 18 21.2772425736 +38 01 35.801359968   19.75 18.05     ~ 1002 2
11 QSO B0420-0127 Bla 04 23 15.80072217 -01 20 33.0656073   17.50 17.00 16.28   ~ 1263 3
12 RX J0433.6+2906 BLL 04 33 37.82985981 +29 05 55.4770576   19.0 17.80 17.06   ~ 181 1
13 QSO B0440-003 Bla 04 42 38.66072366 -00 17 43.4209582   19.59 19.22 17.85   ~ 433 1
14 QSO B0446+113 BLL 04 49 07.67110194 +11 21 28.5963618     20.00 18.58   ~ 305 1
15 QSO B0454-463 Bla 04 55 50.77248730 -46 15 58.6797903   17.89 17.4 16.87   ~ 229 1
16 QSO J0457-2324 Bla 04 57 03.1791422424 -23 24 52.021129572   18.85 18.5 16.56   ~ 435 1
17 4C -02.19 Bla 05 01 12.80988538 -01 59 14.2564557   19.1 18.06 19.04   ~ 624 1
18 QSO B0459+060 Bla 05 02 15.44592827 +06 09 07.4939771   19.7 19.5 18.3   ~ 103 1
19 QSO B0506-612 Bla 05 06 43.98874900 -61 09 40.9939787   17.16 16.85 16.9   ~ 186 2
20 ESO 362-21 BLL 05 22 57.98464178 -36 27 30.8512953   15.26 14.62 14.48   ~ 873 2
21 QSO J0530+13 Bla 05 30 56.41674741 +13 31 55.1494688     20.00 19.35   ~ 1004 1
22 QSO B0537-441 BLL 05 38 50.36155950 -44 05 08.9390233   15.77 16.48 16   ~ 924 2
23 QSO B0537-286 Bla 05 39 54.28147904 -28 39 55.9481236   19.70 20.0 18.789   ~ 314 1
24 QSO B0539-057 Bla 05 41 38.08336552 -05 41 49.4283917     20.4 20.70   ~ 279 1
25 8C 0716+714 BLL 07 21 53.4482942664 +71 20 36.363846516   15.5 15.50 14.27   ~ 1388 1
26 QSO J0738+1742 BLL 07 38 07.39375312 +17 42 18.9981506   16.76 16.22 15.78   ~ 1045 1
27 QSO B0805-077 Bla 08 08 15.53603763 -07 51 09.8865298     19.80 16.71   ~ 291 1
28 7C 080458.39+495918.00 Bla 08 08 39.66628970 +49 50 36.5304041   19.55 19.18 18.34   ~ 389 2
29 7C 082754.29+242103.00 Bla 08 30 52.08619250 +24 10 59.8202919   17.62 17.26 16.30   ~ 563 1
30 QSO B0829+047 BLL 08 31 48.8770033992 +04 29 39.086842884   17.10 16.4 14.55   ~ 511 2
31 4C 71.07 Bla 08 41 24.36528508 +70 53 42.1730435     17.30 16.8   ~ 818 1
32 PG 0851+202 BLL 08 54 48.8749846272 +20 06 30.639583620   15.649 15.146 15.446   ~ 2513 1
33 6C 091740+445437 Bla 09 20 58.45848666 +44 41 53.9850947   18.40 18.16 16.55   ~ 407 1
34 4C 55.17 Bla 09 57 38.1839604096 +55 22 57.754950636   18.24 17.89     ~ 459 1
35 6C 095456+654857 BLL 09 58 47.2451872176 +65 33 54.819354600     17.0 15.75   ~ 771 1
36 RX J1015.0+4926 BLL 10 15 04.1396533776 +49 26 00.706055496   16.56 16.15 14.58   ~ 400 3
37 Z 184-50 BLL 11 04 27.3140835504 +38 12 31.798495872   13.50 12.90 8.31   ~ 2841 1
38 QSO J1130-1449 Bla 11 30 07.0523452128 -14 49 27.388021944   17.17 16.90 16 16.97 ~ 739 1
39 Ton 599 Bla 11 59 31.83391383 +29 14 43.8268224   14.80 14.41 17.652 13.39 ~ 989 1
40 7C 1219+2830 BLL 12 21 31.6904439888 +28 13 58.500308172   16.81 16.11 14.24   ~ 924 1
41 7C 122223.5+213929 Bla 12 24 54.4583146056 +21 22 46.385507388   17.56 17.50 18.2   ~ 770 2
42 3C 273 BLL 12 29 06.6998257176 +02 03 08.597629980   13.05 14.830 14.11   ~ 6022 1
43 4C -02.55 Bla 12 32 00.0159535440 -02 24 04.793069304   17.41 17.06 16.4   ~ 440 1
44 QSO J1246-0730 Bla 12 46 04.23211565 -07 30 46.5746985   17.6 18.0 18.2   ~ 198 1
45 3C 279 Bla 12 56 11.16657958 -05 47 21.5251510   18.01 17.75 15.87   ~ 3205 2
46 QSO B1313-333 Bla 13 16 07.98594757 -33 38 59.1726741   18.04 20.0 17.23   ~ 267 1
47 NAME Centaurus A BLL 13 25 27.61521044 -43 01 08.8050291   8.18 6.84 6.66   ~ 4774 3
48 QSO B1324+224 Bla 13 27 00.86131319 +22 10 50.1628385     18.90 18.80   ~ 194 1
49 QSO B1331+170 Bla 13 33 35.7827544072 +16 49 04.013500728   16.84 16.71 16.41   ~ 469 1
50 QSO B1334-127 Bla 13 37 39.78278132 -12 57 24.6933925   18.5 19.00 16.22   ~ 540 1
51 QSO B1406-076 Bla 14 08 56.48120623 -07 52 26.6665312   20.3 18.4     ~ 336 1
52 QSO B1424-41 Bla 14 27 56.29756617 -42 06 19.4376238   18.48 17.7 16.30   ~ 547 1
53 QSO B1504-167 Bla 15 07 04.78696269 -16 52 30.2671543   18.40 18.50 17.00   ~ 237 1
54 QSO J1512-0906 Bla 15 12 50.53293048 -09 05 59.8297908   16.74 16.54     ~ 1409 1
55 ESO 514-1 BLL 15 17 41.8134049824 -24 22 19.482207024   15.13 14.00 13.95   ~ 815 3
56 4C 15.54 BLL 16 07 06.43046256 +15 51 34.4855829   20.15 19.49 17.5   ~ 181 2
57 4C 10.45 Bla 16 08 46.20318700 +10 29 07.7757424   18.5 18.70 18.03   ~ 409 1
58 6C 161147+342017 Bla 16 13 41.06424322 +34 12 47.9088535   17.98 17.46 17.07   ~ 673 1
59 QSO B1622-253 Bla 16 25 46.89164287 -25 27 38.3268734   21.3 20.6 19.60   ~ 381 1
60 QSO J1626-2951 Bla 16 26 06.02084013 -29 51 26.9712990   18.41 20.5 17.6   ~ 452 1
61 4C 38.41 Bla 16 35 15.49297809 +38 08 04.5005995   18.14 17.97 17.25   ~ 906 1
62 Z 225-7 BLL 16 53 52.21668403 +39 45 36.6088754 14.09 14.15 13.29 8.26   ~ 2304 2
63 QSO B1725+044 Bla 17 28 24.95272284 +04 27 04.9138307   17.43 16.99 16.24   ~ 245 1
64 QSO B1730-130 Bla 17 33 02.70578907 -13 04 49.5482119   18 19.50 18.78 17.39 ~ 1198 1
65 4C 51.37 Bla 17 40 36.97784792 +52 11 43.4073694   18.16 18.70 16.73   ~ 441 1
66 QSO B1741-038 Bla 17 43 58.85613537 -03 50 04.6167326     20.40 17.98   ~ 583 1
67 QSO B1830-211 Bla 18 33 39.9399138048 -21 03 39.368838780     18.70 21   ~ 724 1
68 QSO B1908-202 Bla 19 11 09.65289294 -20 06 55.1090664   18.21   18.14   ~ 306 1
69 QSO B1933-400 Bla 19 37 16.21735889 -39 58 01.5531167   18.15 19 17.43   ~ 209 2
70 QSO B1936-155 Bla 19 39 26.65775171 -15 25 43.0584711   19.44 20.30 18.80   ~ 180 1
71 PKS J2009-4849 BLL 20 09 25.3903899240 -48 49 53.725051056   15.75 12.81 11.41   ~ 604 1
72 QSO B2022-077 BLL 20 25 40.6602562440 -07 35 52.688047128   18.5       ~ 234 3
73 QSO B2032+107 BLL 20 35 22.33330500 +10 56 06.7881888   17.96 16.37 17.4   ~ 218 1
74 QSO B2052-474 Bla 20 56 16.35980507 -47 14 47.6277179   18.29 19.1 18.07   ~ 341 1
75 PKS J2158-3013 BLL 21 58 52.0652249880 -30 13 32.118447792   13.36 13.09 12.62   ~ 1829 1
76 NAME BL Lac BLL 22 02 43.2913536816 +42 16 39.979416792   15.66 14.72     ~ 2397 1
77 QSO B2209+236 Bla 22 12 05.96631459 +23 55 40.5438259   19 20.66 19.69   ~ 257 1
78 4C 11.69 Bla 22 32 36.40890093 +11 43 50.9040592   17.75 17.33     ~ 1205 2
79 3C 454.3 Bla 22 53 57.7480438728 +16 08 53.561508864   16.57 16.10 15.22   ~ 3004 2
80 QSO B2255-2814 Bla 22 58 05.96287687 -27 58 21.2567572   17.34 16.77 17.20   ~ 397 1
81 QSO B2320-035 Bla 23 23 31.95375055 -03 17 05.0238540   18.6   18.16   ~ 229 2
82 6C 234648+383225 Bla 23 49 20.82654326 +38 49 17.5585751   19.1       ~ 55 1
83 6C 235150+453621 Bla 23 54 21.68022501 +45 53 04.2365520   20.6 20.60 19.1   ~ 252 1
84 QSO B2356+196 Bla 23 58 46.0850683944 +19 55 20.303702724     18.0 17.37   ~ 152 1

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