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Register a new userThe Accretion Disc-Jet Connection in Blazars
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Sagnick Mukherjee Mr
Publication date
2019
fields
Physics
and research's language is
English
Authors
Sagnick Mukherjee
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The power spectral density (PSD) of the X-ray emission variability from the accretion disc-corona region of black hole X-ray binaries and active galactic nuclei has a broken power law shape with a characteristic break time-scale. If the disc and the jet are connected, the jet variability may also contain a characteristic time-scale related to that of the disc-corona. Recent observations of the blazar Mrk 421 have confirmed the broken power law shape of the PSD of its jet X-ray variability. We model the time variability of a blazar, in which emitting particles are assumed to be accelerated by successive shock waves flowing down the jet with a varying inter-shock time-scale. We investigate the possible relation between the characteristic time-scales in the disc and jet variability based on the above model, along with mathematically and physically simulated disc variability. We find that both the PSD of the jet and disc variability may have a broken power law shape but the break time-scales are not related in general except only in systems with a small range of BH mass. The break in the jet and the disc PSD are connected to the interval between large amplitude outbursts in the jet (inter-shock time-scale) and to the viscous time-scale in the disc, respectively. In frequency bands where multiple emission processes are involved or emission is from lower energy particles, the break in the PSD may not be prominent enough for detection.
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When the matter from a companion star is accreted towards the central compact accretor, i.e. a black hole (BH) or a neutron star (NS), an accretion disc and a jet outflow will form, providing bight X-ray and radio emission, which is known as X-ray binaries (XRBs). In the low/hard state, there exist disc-jet couplings in XRBs, but it remains uncertain whether the jet power comes from the disc or the central accretor. Moreover, BHXRBs have different properties compared with NSXRBs: quiescent BHXRBs are typically two to three orders of magnitude less luminous than NSXRBs in X-ray, whereas BHXRBs are more radio loud than NSXRBs. In observations, an empirical correlation has been established between radio and X-ray luminosity, $L_{rm R} propto L_{rm X}^b$, where $bsim 0.7$ for BHXRBs and $b sim 1.4$ for non-pulsating NSXRBs. However, there are some outliers of BHXRBs showing unusually steep correlation as NSXRBs at higher luminosities. In this work, under the assumption that the origin of jet power is related to the internal energy of the inner disc, we apply our magnetized, radiatively efficient thin disc model and the well-known radiatively inefficient accretion flow model to NSXRBs and BHXRBs. We find that the observed radio/X-ray correlations in XRBs can be well understood by the disc-jet couplings.
We study the disk-jet connection in supermassive black holes by investigating the properties of their optical and radio emissions utilizing the SDSS-DR7 and the NVSS catalogs. Our sample contains 7017 radio-loud quasars with detection both at 1.4~GHz and SDSS optical spectrum. Using this radio-loud quasar sample, we investigate the correlation among the jet power ($P_{rm jet}$), the bolometric disk luminosity ($L_{rm disk}$), and the black hole mass ($M_{rm BH}$) in the standard accretion disk regime. We find that the jet powers correlate with the bolometric disk luminosities as $log P_{rm jet} = (0.96pm0.012)log L_{rm disk} + (0.79 pm 0.55)$. This suggests that the jet production efficiency of $eta_{rm jet}simeq1.1_{-0.76}^{+2.6}times10^{-2}$ assuming the disk radiative efficiency of $0.1$ implying low black hole spin parameters and/or low magnetic flux for radio-loud quasars. But it can be also due to dependence of the efficiency on geometrical thickness of the accretion flow which is expected to be small for quasars accreting at the disk Eddington ratios $0.01 lesssim lambda lesssim 0.3$. This low jet production efficiency does not significantly increase even if we set the disk radiative efficiency of 0.3. We also investigate the fundamental plane in our samples among $P_{rm jet}$, $L_{rm disk}$, and $M_{rm BH}$. We could not find a statistically significant fundamental plane for radio-loud quasars in the standard accretion regime.
We construct a time-dependent relativistic accretion model for tidal disruption events (TDEs) with an $alpha-$viscosity and the pressure dominated by gas pressure. We also include the mass fallback rate $dot{M}_f$ for both full and partial disruption TDEs, and assume that the infalling debris forms a seed disc in time $t_c$, which evolves due to the mass addition from the infalling debris and the mass loss via accretion onto the black hole. Besides, we derive an explicit form for the disc height that depends on the angular momentum parameter in the disc. We show that the surface density of the disc increases at an initial time due to mass addition, and then decreases as the mass fallback rate decreases, which results in a decrease in the disc mass $M_{rm d}$ with a late-time evolution of $M_{rm d} propto t^{-1.05}$ and $M_{rm d} propto t^{-1.38}$ for full and partial disruption TDEs respectively, where $t$ is the time parameter. The bolometric luminosity $L$ shows a rise and decline that follows a power-law at late times given by $L propto t^{-1.8}$ and $L propto t^{-2.3}$ for full and partial disruption TDEs respectively. Our obtained luminosity declines faster than the luminosity inferred using $L propto dot{M}_f$. We also compute the light curves in various spectral bands.
We present the spectral analysis of three Suzaku XIS observations of 3C 111 requested to monitor the predicted variability of its ultra-fast outflow on ~7 days time-scales. We detect an ionized iron emission line in the first observation and a blue-shifted absorption line in the second, when the flux is ~30% higher. The location of the material is constrained at <0.006pc from the variability. Detailed modelling support an identification with ionized reflection off the accretion disc at ~20-100r_g from the black hole and a highly ionized and massive ultra-fast outflow with velocity ~0.1c, respectively. The outflow is most probably accelerated by radiation pressure, but additional magnetic thrust can not be excluded. The measured high outflow rate and mechanical energy support the claims that disc outflows may have a significant feedback role. This work provides the first direct evidence for an accretion disc-outflow connection in a radio-loud AGN, possibly linked also to the jet activity.
We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4--10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 light-days of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with steeper slope at shorter timescales. The break timescale of 13 (+12,-6) days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons --- the corona --- situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the FR I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole
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