2013MNRAS.433.1764M


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.19CEST15:41:59

2013MNRAS.433.1764M - Mon. Not. R. Astron. Soc., 433, 1764-1777 (2013/August-1)

A high Eddington-ratio, true Seyfert 2 galaxy candidate: implications for broad-line region models.

MINIUTTI G., SAXTON R.D., RODRIGUEZ-PASCUAL P.M., READ A.M., ESQUEJ P., COLLESS M., DOBBIE P. and SPOLAOR M.

Abstract (from CDS):

A bright, soft X-ray source was detected on 2010 July 14 during an XMM-Newton slew at a position consistent with the galaxy GSN 069 (z = 0.018). Previous ROSAT observations failed to detect the source and imply that GSN 069 is now ≥ 240 times brighter than it was in 1994 in the soft X-ray band. Optical spectra (from 2001 to 2003) are dominated by unresolved emission lines with no broad components, classifying GSN 069 as a Seyfert 2 galaxy. We report here results from a ∼ 1yr monitoring with Swift and XMM-Newton, as well as from new optical spectroscopy. GSN 069 is an unabsorbed, ultrasoft source in X-rays, with no flux detected above ∼ 1keV. The soft X-rays exhibit significant variability down to time-scales of hundreds of seconds. The UV-to-X-ray spectrum of GSN 069 is consistent with a pure accretion disc model which implies an Eddington ratio λ ≃ 0.5 and a black hole mass of ≃ 1.2x106M☉. A new optical spectrum, obtained ∼ 3.5months after the XMM-Newton slew detection, is consistent with earlier spectra and lacks any broad-line component. The lack of cold X-ray absorption and the short time-scale variability in the soft X-rays rule out a standard Seyfert 2 interpretation of the source. The present Eddington ratio of GSN 069 exceeds the critical value below which no emitting broad-line region (BLR) forms, according to popular models, so that GSN 069 can be classified as a bona-fide high Eddington-ratio true Seyfert 2 galaxy. We discuss our results within the framework of two possible scenarios for the BLR in AGN, namely the two-phase model (cold BLR clouds in pressure equilibrium with a hotter medium), and models in which the BLR is part of an outflow, or disc-wind. Finally, we point out that GSN 069 may be a member of a population of super-soft active galactic nuclei (AGN) whose spectral energy distribution is completely dominated by accretion disc emission, as it is the case in some black hole X-ray binary transients during their outburst evolution. The disc emission for a typical AGN with black hole mass of 107-108M☉ does not enters the soft X-ray band, so that GSN 069-like objects with larger black hole mass (i.e. the bulk of the AGN population) are missed by current X-ray surveys, or misclassified as Compton-thick candidates. If the analogy between black hole X-ray binary transients and AGN holds, the lifetime of these super-soft states in AGN may be longer than 104 years, implying that the actual population of super-soft AGN may not be negligible, possibly contaminating the estimated fraction of heavily obscured AGN from current X-ray surveys.

Abstract Copyright: © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2013)

Journal keyword(s): accretion, accretion discs - galaxies: active - galaxies: Seyfert - X-rays: galaxies

Simbad objects: 11

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Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 2MASX J01190869-3411305 AGN 01 19 08.6632315880 -34 11 30.521147889   16.226   15.275   ~ 30 0
2 CPD-69 177 WD* 03 10 31.0201840720 -68 36 03.381441176 10.757 11.413 11.394 11.47 11.558 DA3.0 239 0
3 M 81 Sy2 09 55 33.17306143 +69 03 55.0609270   7.89 6.94     ~ 4056 5
4 NGC 3147 Sy2 10 16 53.632 +73 24 02.34   11.43 10.61     ~ 436 2
5 NGC 3660 Sy2 11 23 32.2791583222 -08 39 30.755681618   15.34 14.45     ~ 165 0
6 2XMM J123103.2+110648 AG? 12 31 03.239 +11 06 48.60           ~ 30 0
7 2MASX J13020015+2746579 AGN 13 02 00.1380286789 +27 46 57.858881675   15.4       ~ 63 0
8 NAME Mrk 273x Sy2 13 44 47.4486 +55 54 11.318     20.8     ~ 27 0
9 [GHJ2008] 3 HXB 16 50 00.980 -49 57 43.60     11.89     K4V 358 0
10 2MASX J19271951+6533539 Sy1 19 27 19.5368415554 +65 33 54.331474137     15.4     ~ 40 0
11 QSO B2131-427 Sy2 21 34 26.4 -42 29 58   20.20       ~ 17 0

    Equat.    Gal    SGal    Ecl

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2021.04.19-15:41:59

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