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Register a new userSix Years of Fermi-LAT and Multi-wavelength Monitoring of the Broad-Line Radio Galaxy 3C 120: Jet Dissipation at Sub-parsec Scales from the Central Engine
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We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over six years. Over the past two years, Fermi-LAT sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240-56300, 43 GHz VLBA monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the gamma-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a gamma-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole, if we take the distance of the 43 GHz core from the central black hole as ~ 0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections (Marscher et al. 2002; Chatterjee et al. 2009). Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the gamma rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.
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We present six-year multi-wavelength monitoring result for broad-line radio galaxy 3C 120. The source was sporadically detected by Fermi-LAT and after the MeV/GeV gamma-ray detection the 43 GHz radio core brightened and a knot ejected from an unresolved core, implying that the radio-gamma phenomena are physically connected. We show that the gamma-ray emission region is located at sub-pc distance from the central black hole, and MeV/GeV gamma-ray emission mechanism is inverse-Compton scattering of synchrotron photons. We also discuss future perspective revealed by next-generation X-ray satellite Astro-H.
We carried out photometric and spectroscopic observations of the well-studied broad-line radio galaxy 3C 120 with the Las Cumbres Observatory (LCO) global robotic telescope network from 2016 December to 2018 April as part of the LCO AGN Key Project on Reverberation Mapping of Accretion Flows. Here, we present both spectroscopic and photometric reverberation mapping results. We used the interpolated cross-correlation function (ICCF) to perform multiple-line lag measurements in 3C 120. We find the H$gamma$, He II $lambda 4686$, H$beta$ and He I $lambda 5876$ lags of $tau_{text{cen}} = 18.8_{-1.0}^{+1.3}$, $2.7_{-0.8}^{+0.7}$, $21.2_{-1.0}^{+1.6}$, and $16.9_{-1.1}^{+0.9}$ days respectively, relative to the V-band continuum. Using the measured lag and rms velocity width of the H$beta$ emission line, we determine the mass of the black hole for 3C 120 to be $M=left(6.3^{+0.5}_{-0.3}right)times10^7,(f/5.5)$ M$_odot$. Our black hole mass measurement is consistent with similar previous studies on 3C 120, but with small uncertainties. In addition, velocity-resolved lags in 3C 120 show a symmetric pattern across the H$beta$ line, 25 days at line centre decreasing to 17 days in the line wings at $pm4000$ km s$^{-1}$. We also investigate the inter-band continuum lags in 3C 120 and find that they are generally consistent with $tauproptolambda^{4/3}$ as predicted from a geometrically-thin, optically-thick accretion disc. From the continuum lags, we measure the best fit value $tau_{rm 0} = 3.5pm 0.2$ days at $lambda_{rm 0} = 5477$A. It implies a disc size a factor of $1.6$ times larger than prediction from the standard disc model with $L/L_{rm Edd} = 0.4$. This is consistent with previous studies in which larger than expected disc sizes were measured.
During 1995, the broad-line radio galaxy 3C 390.3 is the subject of a multi-wavelength monitoring campaign comprised of ROSAT HRI, IUE, and ground based optical, infrared and radio observations. We report preliminary results from the monitoring campaign focusing on the X-ray observations. Snapshot ROSAT observations being made every three days show large amplitude variability. The light curve is dominated by a flare near JD 2449800 characterized by a doubling time scale of 9 days and a general increase in flux after the flare. The optical R and I band light curves show a general increase in flux. The ASCA spectra obtained before and after the flare can be described by an absorbed power law. Spectral variability between the two observations is characterized by an increase in power law index by $DeltaGamma sim 0.08$ at higher flux.
We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray, optical, and radio wave bands, as well as imaging with the Very Long Baseline Array (VLBA). Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries. These findings provide support for the paradigm that black hole X-ray binaries and active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central black hole. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the emitting regions from the central BH.
We present unambiguous evidence for a parsec scale wind in the Broad-Line Radio Galaxy (BLRG) 3C 382, the first radio-loud AGN, with $R_{rm L} = log_{10}(f_{rm 5GHz}/f_{4400})>1$, whereby an outflow has been measured with X-ray grating spectroscopy. A 118 ks Chandra grating (HETG) observation of 3C 382 has revealed the presence of several high ionization absorption lines in the soft X-ray band, from Fe, Ne, Mg and Si. The absorption lines are blue-shifted with respect to the systemic velocity of 3C 382 by -840pm60 km/s and are resolved by Chandra with a velocity width of 340pm70 km/s. The outflow appears to originate from a single zone of gas of column density $N_{rm H} = 1.3 times 10^{21}$ cm$^{-2}$ and ionization parameter $log xi = 2.45$. From the above measurements we calculate that the outflow is observed on parsec scales, within the likely range from 10-1000 pc, i.e., consistent with an origin in the Narrow Line Region.
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