2007A&A...473..105M

Query : 2007A&A...473..105M

2007A&A...473..105M - Astronomy and Astrophysics, volume 473105-120 (2007/10-1)

XMM-Newton observations of the Lockman Hole. V. Time variability of the brightest AGN.

MATEOS S., BARCONS X., CARRERA F.J., PAGE M.J., CEBALLOS M.T., HASINGER G. and FABIAN A.C.

Abstract (from CDS):

This paper presents the results of a study of X-ray spectral and flux variability on time scales from months to years, of the 123 brightest objects (including 46 type-1 AGN and 28 type-2 AGN) detected with XMM-Newton in the Lockman Hole field. We detected flux variability with a significance ≥3σ in ∼50% of the objects, including 68±11% and 48±15% among our samples of type-1 and type-2 AGN. However we found that the fraction of sources with best quality light curves that exhibit flux variability on the time scales sampled by our data is ≥80%, i.e the great majority of the AGN population may actually vary in flux on long time scales. The mean relative intrinsic amplitude of flux variability was found to be ∼0.15 although with a large dispersion in measured values, from ∼0.1 to ∼0.65. The flux variability properties of our samples of AGN (fraction of variable objects and amplitude of variability) do not significantly depend on the redshift or X-ray luminosity of the objects and seem to be similar for the two AGN types. Using a broad band X-ray colour we found that the fraction of sources showing spectral variability with a significance ≥3σ is ∼40% i.e. less common than flux variability. Spectral variability was found to be more common in type-2 AGN than in type-1 AGN with a significance of more than 99%. This result is consistent with the fact that part of the soft emission in type-2 AGN comes from scattered radiation, and this component is expected to be much less variable than the hard component. The observed flux and spectral variability properties of our objects and especially the lack of correlation between flux and spectral variability in most of them cannot be explained as being produced by variability of one spectral component alone, for example changes in Γ associated with changes in the mass accretion rate, or variability in the amount of X-ray absorption. At least two spectral components must vary in order to explain the X-ray variability of our objects.

Abstract Copyright: ∼

Journal keyword(s): X-rays: general - galaxies: active

VizieR on-line data: <Available at CDS (J/A+A/473/105): table4.dat>

Simbad objects: 124

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Number of rows : 124
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 NAME Lockman Hole reg 10 45 00.0 +58 00 00           ~ 910 0
2 SDSS J105005.73+573108.9 QSO 10 50 05.735 +57 31 08.90           ~ 8 0
3 2XMM J105009.5+573145 Sy1 10 50 09.5330050656 +57 31 43.960092204     20.70     ~ 9 0
4 [VV98] J105019.8+572812 QSO 10 50 19.7237 +57 28 12.866     18.70     ~ 16 0
5 [VV98] J105039.6+572337 QSO 10 50 39.5438741904 +57 23 36.609192456   19.85 19.55 19.14   ~ 47 1
6 [MBC2005] 343 X 10 50 41.22 +57 30 23.3           ~ 2 0
7 RX J1050.7+5717 SyG 10 50 46.02216 +57 17 33.8352           ~ 11 0
8 [MBC2005] 187 X 10 50 47.96 +57 25 22.7           ~ 2 0
9 [MBC2005] 537 X 10 50 50.04 +57 38 21.8           ~ 2 0
10 [MBC2005] 108 X 10 50 50.91 +57 22 15.6           ~ 2 0
11 [VV98] J105104.0+573054 QSO 10 51 03.930 +57 30 54.72     20.30     ~ 13 0
12 RDS 43A AGN 10 51 05.1 +57 19 23           ~ 10 0
13 SDSS J105106.36+573435.8 rG 10 51 06.46 +57 34 35.6           ~ 7 0
14 2XMM J105106.6+571531 AG? 10 51 06.663 +57 15 30.82           ~ 4 0
15 ISO-LHDS J105108+573343 rG 10 51 08.38 +57 33 45.4           ~ 14 0
16 2XMM J105111.7+572635 AG? 10 51 11.711 +57 26 34.57           ~ 7 0
17 2XMM J105114.4+571615 AGN 10 51 14.414 +57 16 15.74   22.59 21.61     ~ 10 0
18 [MBC2005] 601 X 10 51 15.91 +57 42 08.6           ~ 2 0
19 RDS 46A AGN 10 51 20.10 +57 18 48.9           ~ 12 0
20 [MBC2005] 226 X 10 51 20.66 +57 27 01.7           ~ 4 0
21 [MBC2005] 174 X 10 51 20.82 +57 24 58.5           ~ 3 0
22 2XMM J105125.3+573050 Sy1 10 51 25.3238423736 +57 30 50.338701036     19.30     ~ 13 0
23 2MASS J10512806+5735025 rG 10 51 28.0782706224 +57 35 02.482737648           ~ 18 0
24 [BCH2008] 243 X 10 51 28.23 +57 27 40.1           ~ 5 0
25 SDSS J105129.90+573737.4 QSO 10 51 29.903 +57 37 37.46           ~ 11 0
26 SDSS J105137.18+573754.7 QSO 10 51 37.1871160032 +57 37 54.711781788           ~ 16 0
27 2XMM J105137.3+573043 AGN 10 51 37.302 +57 30 42.98           ~ 13 0
28 XMMU J105142.0+573555 rG 10 51 42.07 +57 35 55.2       24.19   ~ 8 0
29 [VV2006] J105144.7+572806 Sy1 10 51 44.91 +57 28 08.0     21.20     ~ 12 0
30 [MBC2005] 351 AGN 10 51 46.57 +57 30 36.6           ~ 6 0
31 [MBC2005] 16 X 10 51 46.97 +57 17 15.0           ~ 3 0
32 SDSS J105148.73+573248.7 rG 10 51 48.732 +57 32 48.71     23.2 22.90   ~ 28 0
33 2XMM J105149.9+572521 AGN 10 51 49.914 +57 25 21.75           ~ 6 0
34 2XMM J105152.0+573906 AGN 10 51 52.151 +57 39 06.39           ~ 5 0
35 2XMM J105154.3+573437 Sy1 10 51 54.377 +57 34 37.79     20.00     ~ 19 0
36 2XMM J105154.5+572407 QSO 10 51 54.71 +57 24 07.4           ~ 7 0
37 [LGE2006] 12 Sy1 10 52 00.11 +57 24 23.5     22.4     ~ 17 0
38 2XMM J105200.3+571806 AGN 10 52 00.41 +57 18 06.2           ~ 10 0
39 [MBC2005] 142 X 10 52 04.00 +57 23 38.9           ~ 3 0
40 [MBC2005] 2045 X 10 52 04.47 +57 41 15.6           ~ 2 0
41 2XMM J105205.9+574122 QSO 10 52 06.1195273056 +57 41 24.394878636           ~ 7 0
42 2MASS J10520626+5715245 AGN 10 52 06.2807459376 +57 15 23.712201684           ~ 11 0
43 2XMM J105206.6+572924 AGN 10 52 06.699 +57 29 24.61           ~ 7 0
44 2XMM J105207.4+573838 Sy1 10 52 07.379 +57 38 38.05     22.40     ~ 9 0
45 [MBC2005] 557 X 10 52 07.79 +57 39 04.6           ~ 3 0
46 [MBH2002] 80 X 10 52 07.92 +57 34 14.5           ~ 4 0
47 3XMM J105209.6+572104 Sy1 10 52 09.708 +57 21 04.54     21.70     ~ 18 0
48 2XMM J105213.2+573221 Sy1 10 52 13.256 +57 32 21.56   21.50 21.38     ~ 19 0
49 RDS 84 rG 10 52 16.95 +57 20 18.0           ~ 13 0
50 2XMM J105219.5+572214 AGN 10 52 19.571 +57 22 13.68           ~ 5 0
51 RX J105220.1+572307 X 10 52 20.17 +57 23 06.8           ~ 5 0
52 2XMM J105223.3+574121 QSO 10 52 23.3479028784 +57 41 21.453919008           ~ 6 0
53 2XMM J105224.5+573009 AGN 10 52 24.615 +57 30 09.41           ~ 16 0
54 2XMM J105225.0+572304 AGN 10 52 25.046 +57 23 05.19           ~ 13 0
55 XMMU J105225.5+572551 AGN 10 52 25.50 +57 25 50.7         23.80 ~ 7 0
56 RDS 108 AGN 10 52 28.00 +57 33 30.7           ~ 4 0
57 RDS 18 Sy1 10 52 28.34 +57 31 04.3           ~ 10 0
58 [VV98] J105230.1+573913 QSO 10 52 30.0812803008 +57 39 13.483856772   21.75 21.00     ~ 17 0
59 [BCH2008] 179 X 10 52 31.85 +57 25 00.6           ~ 4 0
60 [FFH2002] 115 AGN 10 52 32.18 +57 24 28.2           ~ 5 0
61 [MBC2005] 26 X 10 52 33.07 +57 17 49.3           ~ 3 0
62 2XMM J105236.2+571602 QSO 10 52 36.203 +57 16 02.11           ~ 6 0
63 [MBH2002] 46 AGN 10 52 37.18 +57 34 00.4           ~ 5 0
64 NVSS J105237+573101 rG 10 52 37.355 +57 31 03.76       21.25   ~ 19 1
65 SDSS J105238.15+573322.3 rG 10 52 38.158 +57 33 22.38     22.4     ~ 8 0
66 [VV98] J105239.6+572432 QSO 10 52 39.5958253296 +57 24 31.425574788   18.39 18.07     ~ 76 0
67 2XMM J105241.5+573650 Sy2 10 52 41.5486629408 +57 36 50.089091364           ~ 12 0
68 [MBH2002] 98 X 10 52 41.78 +57 30 38.1           ~ 4 0
69 2XMM J105242.2+573158 Sy1 10 52 42.38 +57 31 58.3     25.2 25.00   ~ 18 0
70 [VV98] J105243.3+571545 QSO 10 52 43.1559083808 +57 15 44.442070236   20.66 20.46     ~ 24 0
71 RX J105243.4+572800 AGN 10 52 43.51 +57 27 59.5     24.7     ~ 7 0
72 [VV98] J105244.8+572123 QSO 10 52 44.7211227504 +57 21 22.457174220   21.18 20.86     ~ 26 0
73 RDS 801A Sy1 10 52 45.39 +57 37 45.9           ~ 10 0
74 2XMM J105247.9+572116 Sy1 10 52 48.0450883248 +57 21 16.654430304   20.84 20.34     ~ 27 0
75 [MBH2002] 61 X 10 52 48.42 +57 41 28.8           ~ 4 0
76 RX J105251.2+572011 X 10 52 51.16 +57 20 13.3           ~ 4 0
77 2XMM J105251.4+573200 AGN 10 52 51.519 +57 32 00.56           ~ 7 0
78 SDSS J105252.03+573134.6 G 10 52 52.039 +57 31 34.63           ~ 6 0
79 2MASS J10525274+5728596 Sy2 10 52 52.7604722568 +57 28 59.623234140     17.8     ~ 23 0
80 SDSS J105254.23+572341.9 Sy1 10 52 54.45 +57 23 42.4     23.1 22.11   ~ 14 0
81 NVSS J105254+571950 rG 10 52 55.3254 +57 19 50.471     24.6 23.88   ~ 15 1
82 [VV98] J105257.3+572507 QSO 10 52 57.1388606136 +57 25 06.850948620   22.09 21.48     ~ 24 0
83 2XMM J105258.2+572251 AGN 10 52 58.174 +57 22 50.91           ~ 7 0
84 [VV98] J105259.3+573030 QSO 10 52 59.163 +57 30 29.98     21.70     ~ 16 0
85 2XMM J105259.7+573155 Sy1 10 52 59.819 +57 31 54.72     21.50     ~ 14 0
86 [MBC2005] 607 X 10 53 01.691 +57 14 59.15           ~ 5 0
87 2XMM J105302.4+573756 Sy1 10 53 02.412 +57 37 56.83   21.47 21.48     ~ 18 0
88 RDS 827A rG 10 53 03.43 +57 35 30.8     21.8     ~ 4 0
89 2XMM J105303.7+572924 Sy1 10 53 03.759 +57 29 24.07           ~ 12 0
90 XMMU J105305.6+572810 Sy1 10 53 05.66 +57 28 10.1       23.10   ~ 13 0
91 3XMM J105306.0+573424 Sy1 10 53 06.0540527592 +57 34 24.595144572   20.71 20.46     ~ 27 0
92 [VV98] J105307.4+571505 QSO 10 53 07.3241878632 +57 15 04.632919200     20.30     ~ 24 0
93 2XMM J105309.2+572821 Sy1 10 53 09.2926190448 +57 28 20.539401312   21.15 20.85     ~ 24 0
94 [MBC2005] 86 AGN 10 53 09.78 +57 20 57.5           ~ 4 0
95 RDS 634 Sy1 10 53 11.80 +57 23 07.0           ~ 8 0
96 2XMM J105312.2+572506 Sy1 10 53 12.239 +57 25 06.20           ~ 11 0
97 RDS 804 Sy1 10 53 12.50 +57 34 24.7           ~ 10 0
98 RDS 430 X 10 53 15.23 +57 26 29.4           ~ 4 0
99 ISO-LHDS J105315+572449 AGN 10 53 15.76 +57 24 48.6           ~ 8 0
100 [VV98] J105316.9+573552 QSO 10 53 16.7644541304 +57 35 50.730680004   19.97 19.47     ~ 69 0
101 SDSS J105319.02+571851.8 rG 10 53 19.023 +57 18 51.81     21.3 20.84   ~ 19 0
102 [MBH2002] 85 X 10 53 21.69 +57 31 47.2           ~ 4 0
103 SDSS J105322.10+572851.2 Sy1 10 53 22.107 +57 28 51.23     22.70     ~ 10 0
104 ISO-LHDS J105324+572823 Sy1 10 53 24.67 +57 28 18.9     22.4     ~ 11 0
105 2XMM J105329.3+572104 AGN 10 53 29.409 +57 21 04.20           ~ 17 0
106 [VV98] J105331.8+572454 QSO 10 53 31.7346910536 +57 24 54.112156956   20.32 20.20     ~ 23 0
107 2XMM J105334.9+572542 AGN 10 53 35.0308257600 +57 25 42.141068976     19.50     ~ 25 0
108 [MBC2005] 518 X 10 53 36.33 +57 37 26.4           ~ 3 0
109 [MBC2005] 511 AGN 10 53 38.33 +57 36 54.6           ~ 5 0
110 2XMM J105339.6+573104 Sy1 10 53 39.7417789968 +57 31 04.402572060   19.97 19.79     ~ 23 0
111 [VV98] J105345.0+572840 QSO 10 53 44.864 +57 28 40.36   21.27 21.19     ~ 23 0
112 [MBH2002] 86 X 10 53 46.90 +57 26 06.2           ~ 4 0
113 RDS 805A Sy1 10 53 47.37 +57 33 50.0     22.6     ~ 10 0
114 [MBH2002] 47 X 10 53 48.15 +57 28 16.3           ~ 5 0
115 SDSS J105348.77+573034.0 rG 10 53 48.774 +57 30 34.08     23.3     ~ 18 0
116 [VV98] J105350.3+572710 QSO 10 53 50.2208736432 +57 27 09.506758536   20.68 20.56     ~ 25 0
117 [MBC2005] 222 AGN 10 53 51.77 +57 27 02.6           ~ 4 0
118 2XMM J105357.0+573241 Sy1 10 53 57.1420052568 +57 32 41.506734336   21.71 21.31     ~ 12 0
119 NVSS J105400+573322 rG 10 54 00.486 +57 33 21.17       26.04   ~ 12 1
120 2XMM J105407.1+573524 QSO 10 54 07.1905066728 +57 35 24.391506876           ~ 9 0
121 SDSS J105411.03+573055.9 G 10 54 11.03424 +57 30 55.9656           ~ 5 0
122 2MASS J10542112+5725431 Sy1 10 54 21.1984001400 +57 25 44.284004364       18.80   ~ 47 1
123 NVSS J105427+573646 rG 10 54 26.231 +57 36 49.19       19.11   ~ 15 1
124 2XMM J105459.4+572218 AG? 10 54 59.43 +57 22 18.8           ~ 3 0

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