Study of LINER sources with broad Hαemission

Abstract

Context. The geometry and physical properties of the accretion mode, and the radiative processes occurring in AGN-powered low ionization nuclear emission-line regions (LINERs) remain a riddle. Both a standard thin accretion disk and an inner-hot radiativelyinefficient accretion flow (RIAF) have been invoked. Models depending on only a jet have also been invoked to explain the broad-band spectral energy distribution (SED) of LINERs. Aims. We attempt to infer the accretion mechanism and radiative processes giving rise to the SEDs of a well-defined optically-selected sample of LINERs showing a definite detection of broad Hα emission (LINER 1s). Methods. We construct SEDs for six LINER 1s with simultaneous UV and X-ray fluxes, and we looked for multiwavelength, radio to X-ray and UV to X-ray, correlations. Results. At a given X-ray luminosity, the average SED of the six LINER 1s in our sample: (1) resembles the SED of radio-loud quasars in the radio band, log R X ≈ −2.7, (2) exhibits a weak UV bump, α ox ≈ −1.17 ± 0.02 with a dispersion σ = 0.01, and (3) displays a X-ray spectrum similar to radio-quiet quasars. The bolometric luminosities inferred from the SEDs of these LINER 1s are extremely faint, at least two orders of magnitude lower than AGN. The X-ray bolometric correction, κ 2−10 keV , of our sample is lower than in the case of AGN, with a mean value of 16. We find a strong anticorrelation between the radio loudness parameter, R X , and the Eddington ratio for our sample, confirming previous results. Moreover, we find a positive correlation between the radio luminosity and the X-ray luminosity which places AGN-powered LINERs, on a radio-power scale, right between low luminosity Seyferts and low luminosity radio galaxies. We complement our α ox list with values derived on a well defined sample of UV-variable LINERs, and establish a strong positive correlation between α ox (considering negative values) and the Eddington ratio, in contrast to the correlation found for luminous AGN. Lastly, we tested two different fundamental planes existing in the literature on our sample, in an attempt to put constraints on the debated origin of the X-ray emission, "RIAF versus jet". The results came contradictory with one pointing toward a RIAF-dominated X-ray emission process and the other pointing toward a jet domination.

X-ray spectral variability of LINERs selected from the Palomar sample

“…At UV frequencies, Younes et al (2012) derived the luminosities from the OM onboard XMM-Newton with UVW2 and UVM2 filters that agree with our results. Variability cannot be studied since OM data are only available at one epoch.…”

“…At UV frequencies, Younes et al (2012) studied this galaxy with XMM-Newton, but the nucleus was not detected, so they estimated upper limits for the flux in one epoch. et al (1997) optically classified this galaxy as a type 2 LINER.…”

Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation

“…Moreover, this model predicts that the correlation should steepen when the luminosity of the system is lower than L crit /L Edd , because then both the radio and X-ray radiation will be dominated by the jet. This prediction is well confirmed by observations of lowluminosity AGNs (e.g., Wrobel et al 2008;de Gasperin et al 2011;Younes et al 2012). However, three quiescent BHBs currently available (XTE J1118+480 - Gallo et al 2014; A 0620-00 - Gallo et al 2006;and V404 Cyg -Corbel, Koerding & Kaaret 2008) apparently do not confirm the prediction.…”

“…Therefore, when the luminosity is below a critical value L crit , we predict the Xray emission will be dominated by the synchrotron emission from the jet . This prediction has been confirmed for observations of the faint LLAGNs and the quiescent state of BHBs (e.g., Wu, Yuan & Cao 2007;Pellegrini et al 2007;Wrobel et al 2008;Pszota et al 2008;Yuan, Yu & Ho 2009;de Gasperin et al 2011;Younes et al 2012;Xie, Yang & Ma 2014).…”

A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998

“…The radio core is known to be variable (see also Sect. 3.1) and NGC 3998 also shows variability in the ultraviolet (Maoz et al 2005) and X-ray (Younes et al 2012;Hernández-García et al 2013) regimes. At X-ray energies, NGC 3998 contains a nuclear source with L X (2-10 keV) ∼ 2.5 × 10 41 erg s −1 (Terashima et al 2000;Ptak et al 2004).…”