2017A&A...608A..32F


Query : 2017A&A...608A..32F

2017A&A...608A..32F - Astronomy and Astrophysics, volume 608A, 32-32 (2017/12-1)

The XMM deep survey in the CDF-S. X. X-ray variability of bright sources.

FALOCCO S., PAOLILLO M., COMASTRI A., CARRERA F.J., RANALLI P., IWASAWA K., GEORGANTOPOULOS I., VIGNALI C. and GILLI R.

Abstract (from CDS):

Aims. We aim to study the variability properties of bright hard X-ray selected active galactic nuclei (AGN) in the redshift range between 0.3 and 1.6 detected in the Chandra Deep Field South (XMM-CDFS) by a long (∼3 Ms) XMM observation.
Methods. Taking advantage of the good count statistics in the XMM CDFS, we search for flux and spectral variability using the hardness ratio (HR) techniques. We also investigate the spectral variability of different spectral components (photon index of the power law, column density of the local absorber, and reflection intensity). The spectra were merged in six epochs (defined as adjacent observations) and in high and low flux states to understand whether the flux transitions are accompanied by spectral changes.
Results. The flux variability is significant in all the sources investigated. The HRs in general are not as variable as the fluxes, in line with previous results on deep fields. Only one source displays a variable HR, anti-correlated with the flux (source 337). The spectral analysis in the available epochs confirms the steeper when brighter trend consistent with Comptonisation models only in this source at 99% confidence level. Finding this trend in one out of seven unabsorbed sources is consistent, within the statistical limits, with the 15% of unabsorbed AGN in previous deep surveys. No significant variability in the column densities, nor in the Compton reflection component, has been detected across the epochs considered. The high and low states display in general different normalisations but consistent spectral properties.
Conclusions. X-ray flux fluctuations are ubiquitous in AGN, though in some cases the data quality does not allow for their detection. In general, the significant flux variations are not associated with spectral variability: photon index and column densities are not significantly variable in nine out of the ten AGN over long timescales (from three to six and a half years). Photon index variability is found only in one source (which is steeper when brighter) out of seven unabsorbed AGN. The percentage of spectrally variable objects is consistent, within the limited statistics of sources studied here, with previous deep samples.

Abstract Copyright: © ESO, 2017

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

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 [LBX2017] 168 AGN 03 32 07.94 -27 37 32.1   23.65 23.35 24.030 22.08 ~ 25 0
2 [VV2006] J033208.7-274735 QSO 03 32 08.6729857488 -27 47 34.647814356 19.78 19.4713 19.11 18.665 18.6210 ~ 85 0
3 ATCDFS9 J033211.65-273726.3 QSO 03 32 11.6527196760 -27 37 26.270285880   19.23 18.90 18.88   ~ 39 0
4 [VV2006] J033227.0-274105 QSO 03 32 27.0132796944 -27 41 05.357500044 19.93 19.3746   19.003 19.1163 ~ 84 0
5 2XMM J033228.5-273537 EmG 03 32 28.58 -27 35 37.1       19.617   ~ 21 0
6 ACS-GC 90043401 QSO 03 32 38.1232741056 -27 39 45.158278032 20.89 20.9342 20.511 20.804 20.6297 ~ 61 0
7 ATCDFS J033238.95-275700.6 AGN 03 32 38.9187869184 -27 57 00.810546876   20.195 19.55 18.857 18.45 ~ 47 0
8 [LBX2017] 785 AGN 03 32 42.640 -27 38 15.50   28.17 23.88 23.57 25.82 ~ 29 0
9 2XMM J033247.8-274232 QSO 03 32 47.886 -27 42 32.82   22.51 22.12 21.65 20.51 ~ 44 0
10 2XMM J033301.6-275818 QSO 03 33 01.7077508784 -27 58 18.887579508   20.34 20.37 20.32 20.04 ~ 31 0

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2022.11.28-12:21:39

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