Query : 2015A&A...577A...8G

2015A&A...577A...8G - Astronomy and Astrophysics, volume 577A, 8-8 (2015/5-1)

Revealing a hard X-ray spectral component that reverberates within one light hour of the central supermassive black hole in Ark 564.


Abstract (from CDS):

Arakelian 564 (Ark 564, z=0.0247) is an X-ray-bright narrow-line Seyfert 1 galaxy. By using advanced X-ray timing techniques, an excess of ''delayed'' emission in the hard X-ray band (4-7.5keV) following about 1000s after ''flaring'' light in the soft X-ray band (0.4-1keV) was recently detected. We report on the X-ray spectral analysis of eight XMM-Newton and one Suzaku observation of Ark 564. Our aim is to characterise the X-ray spectral properties of the source in the light of these recently reported results. High-resolution spectroscopy was performed with the RGS in the soft X-ray band, while broad-band spectroscopy was performed with the EPIC-pn and XIS/PIN instruments. We analysed time-averaged, flux-selected, and time-resolved spectra. Despite the strong variability in flux during our observational campaign, the broad-band spectral shape of Ark 564 does not vary dramatically and can be reproduced either by a superposition of a power law and a blackbody emission or by a Comptonized power-law emission model. High-resolution spectroscopy revealed ionised gas along the line of sight at the systemic redshift of the source, with a low column density (NH∼1021cm–2) and a range of ionisation states (-0.8<log(ξ/erg cm/s)<2.4). Broad-band spectroscopy revealed a very steep intrinsic continuum (photon index Γ∼2.6) and a rather weak emission feature in the iron K band (EW∼150eV); modelling this feature with a reflection component requires highly ionised gas, log(ξ/erg cm/s)>3.5. A reflection-dominated or an absorption-dominated model are similarly able to well reproduce the time-averaged data from a statistical point of view, in both cases requiring contrived geometries and/or unlikely physical parameters. Finally, through time-resolved analysis we spectroscopically identified the ''delayed'' emission as a spectral hardening above ∼4keV; the most likely interpretation for this component is a reprocessing of the ''flaring'' light by gas located at 10-100rg from the central supermassive black hole that is so hot that it can Compton-upscatter the flaring intrinsic continuum emission.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: individual: Ark 564 - galaxies: Seyfert - X-rays: individuals: Ark 564 - black hole physics

Simbad objects: 6

goto Full paper

goto View the references in ADS

Number of rows : 6
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 LB 1727 Sy1 04 26 00.7188165240 -57 12 01.769902992 13.68 14.58 14.37 14.8   ~ 266 0
2 Mrk 1095 Sy1 05 16 11.4092471904 -00 08 59.157166920   14.30 13.92     ~ 856 1
3 LBQS 1244+0238 Sy1 12 46 35.2527826632 +02 22 08.782546368   16.57 16.37     ~ 286 0
4 NGC 5548 Sy1 14 17 59.5400291832 +25 08 12.603122268   14.35 13.73     ~ 2602 0
5 Mrk 509 Sy1 20 44 09.7504483224 -10 43 24.727155528   13.35 13.12 10.7   ~ 1232 0
6 UGC 12163 Sy1 22 42 39.3363009144 +29 43 31.302092640   14.86 14.16     ~ 676 1

To bookmark this query, right click on this link: simbad:objects in 2015A&A...577A...8G and select 'bookmark this link' or equivalent in the popup menu


© Université de Strasbourg/CNRS

    • Contact