In 2016 we carried out a Swift monitoring programme to track the X-ray hardness variability of eight type-I AGN over a year. The purpose of this monitoring was to find intense obscuration events in ...AGN, and thereby study them by triggering joint XMM-Newton, NuSTAR, and HST observations. We successfully accomplished this for NGC 3783 in December 2016. We found heavy X-ray absorption produced by an obscuring outflow in this AGN. As a result of this obscuration, interesting absorption features appear in the UV and X-ray spectra, which are not present in the previous epochs. Namely, the obscuration produces broad and blue-shifted UV absorption lines of Lyα, C iv, and N v, together with a new high-ionisation component producing Fe xxv and Fe xxvi absorption lines. In soft X-rays, only narrow emission lines stand out above the diminished continuum as they are not absorbed by the obscurer. Our analysis shows that the obscurer partially covers the central source with a column density of few 1023 cm-2, outflowing with a velocity of few thousand km s-1. The obscuration in NGC 3783 is variable and lasts for about a month. Unlike the commonly seen warm-absorber winds at pc-scale distances from the black hole, the eclipsing wind in NGC 3783 is located at about 10 light days. Our results suggest that the obscuration is produced by an inhomogeneous and clumpy medium, consistent with clouds in the base of a radiatively driven disk wind at the outer broad-line region of the AGN.
We employ optical and ultraviolet (UV) observations to present spectral energy distributions (SEDs) for two reverberation-mapped samples of super-Eddington and sub-Eddington active galactic nuclei ...(AGN) with similar luminosity distributions. The samples are fitted with accretion disc (AD) models in order to look for SED differences that depend on the Eddington ratio. The fitting takes into account measured black hole (BH) mass and accretion rates, BH spin and intrinsic reddening of the sources. All objects in both groups can be fitted by thin AD models over the range 0.2–1 μm with reddening as a free parameter. The intrinsic reddening required to fit the data are relatively small, E(B − V) ≤ 0.2 mag, except for one source. Super-Eddington AGN seems to require more reddening. The distribution of E(B − V) is similar to what is observed in larger AGN samples. The best-fitting disc models recover very well the BH mass and accretion for the two groups. However, the SEDs are very different, with super-Eddington sources requiring much more luminous far-UV continuum. The exact amount depends on the possible saturation of the UV radiation in slim discs. In particular, we derive for the super-Eddington sources a typical bolometric correction at 5100 Å of 60–150 compared with a median of ∼20 for the sub-Eddington AGN. The measured torus luminosity relative to λL
λ(5100 Å) are similar in both groups. The αOX distribution is similar too. However, we find extremely small torus covering factors for super-Eddington sources, an order of magnitude smaller than those of sub-Eddington AGN. The small differences between the groups regarding the spectral range 0.2–22 μm, and the significant differences related to the part of the SED that we cannot observe may be consistent with some slim disc models. An alternative explanation is that present day slim-disc models overestimate the far-UV luminosity of such objects by a large amount.
Context. Broad emission lines originate in the surroundings of supermassive black holes in the centers of active galactic nuclei (AGN). These broad-line emitting regions are spatially unresolved even ...for the nearest AGN. The origin and geometry of broad-line region (BLR) gas and their connection with geometrically thin or thick accretion disks is of fundamental importance for the understanding of AGN activity. Aims. One method to investigate the extent, structure, and kinematics of the BLR is to study the continuum and line profile variability in AGN. We selected the radio-loud Seyfert 1 galaxy 3C 120 as a target for this study. Methods. We took spectra with a high signal-to-noise ratio of 3C 120 with the 9.2 m Hobby-Eberly Telescope between Sept. 2008 and March 2009. In parallel, we photometrically monitored the continuum flux at the Wise observatory. We analyzed the continuum and line profile variations in detail (1D and 2D reverberation mapping) and modeled the geometry of the line-emitting regions based on the line profiles. Results. We show that the BLR in 3C 120 is stratified with respect to the distance of the line-emitting regions from the center with respect to the line widths (FWHM) of the rms profiles and with respect to the variability amplitude of the emission lines. The emission line wings of Hα and Hβ respond much faster than their central region. This is explained by accretion disk models. In addition, these lines show a stronger response in the red wings. However, the velocity-delay maps of the helium lines show a stronger response in the blue wing. Furthermore, the He ii λ4686 line responds faster in the blue wing in contradiction to observations made one and a half years later when the galaxy was in a lower state. The faster response in the blue wing is an indication for central outflow motions when this galaxy was in a bright state during our observations. The vertical BLR structure in 3C 120 coincides with that of other AGN. We confirm the general trend: the emission lines of narrow line AGN originate at larger distances from the midplane than AGN with broader emission lines.
We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple ...line measurements, we find that the highest precision measure of the virial product c tau Delta V super(2)/G, where tau is the emission-line lag relative to continuum variations and Delta V is the emission-line width, is obtained by using the cross-correlation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to FWHM) for the line width and by measuring the line width in the variable part of the spectrum. Accurate line-width measurement depends critically on avoiding contaminating features, in particular the narrow components of the emission lines. We find that the precision (or random component of the error) of reverberation-based black hole mass measurements is typically around 30%, comparable to the precision attained in measurement of black hole masses in quiescent galaxies by gas or stellar dynamical methods. Based on results presented in a companion paper by Onken et al., we provide a zero-point calibration for the reverberation-based black hole mass scale by using the relationship between black hole mass and host-galaxy bulge velocity dispersion. The scatter around this relationship implies that the typical systematic uncertainties in reverberation-based black hole masses are smaller than a factor of 3. We present a preliminary version of a mass-luminosity relationship that is much better defined than any previous attempt. Scatter about the mass-luminosity relationship for these AGNs appears to be real and could be correlated with either Eddington ratio or object inclination.
Aims.
We present the results of an intensive six-month optical continuum reverberation mapping campaign of the Seyfert 1 galaxy PG 2130+099 at redshift
z
= 0.063. The ground-based photometric ...monitoring was conducted on a daily basis with the robotic 46 cm telescope of the WISE observatory located in Israel. Specially designed narrowband filters were used to observe the central engine of the active galactic nucleus (AGN), avoiding line contamination from the broad-line region (BLR). We aim to measure inter-band continuum time lags across the optical range and determine the size-wavelength relation for this system.
Methods.
We used two methods, the traditional point-spread function photometry and the recently developed proper image subtraction technique, to independently perform the extraction of the continuum light curves. The inter-band time lags are measured with several methods, including the interpolated cross-correlation function, the
z
-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic mode), and MICA.
Results.
PG 2130+099 displays correlated variability across the optical range, and we successfully detect significant time lags of up to ∼3 days between the multiband light curves. We find that the wavelength-dependent lags,
τ
(
λ
), generally follow the relation
τ
(
λ
)∝
λ
4/3
, as expected for the temperature radial profile
T
∝
R
−3/4
of an optically thick, geometrically thin accretion disk. Despite that, the derived time lags can also be fitted by
τ
(
λ
)∝
λ
2
, implying the possibility of a slim, rather than thin, accretion disk. Using the flux variation gradient method, we determined the AGN’s host-galaxy-subtracted rest frame 5100 Å luminosity at the time of our monitoring campaign with an uncertainty of ∼18% (
λL
5100
= (2.40 ± 0.42)×10
44
erg s
−1
). While a continuum reprocessing model can fit the data reasonably well, our derived disk sizes are a factor of ∼2 − 6 larger than the theoretical disk sizes predicted from the AGN luminosity estimate of PG 2130+099. This result is in agreement with previous studies of AGN/quasars and suggests that the standard Shakura-Sunyaev disk theory has limitations in describing AGN accretion disks.
Aims. A strong X-ray outburst was detected in HE 1136-2304 in 2014. Accompanying optical spectra revealed that the spectral type has changed from a nearly Seyfert 2 type (1.95), classified by spectra ...taken 10 and 20 years ago, to a Seyfert 1.5 in our most recent observations. We seek to investigate a detailed spectroscopic campaign on the spectroscopic properties and spectral variability behavior of this changing look AGN and compare this to other variable Seyfert galaxies. Methods. We carried out a detailed spectroscopic variability campaign of HE 1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014 December and 2015 July. Results. The broad-line region (BLR) of HE 1136-2304 is stratified with respect to the distance of the line-emitting regions. The integrated emission line intensities of Hα, Hβ, He I λ5876, and He II λ4686 originate at distances of 15.0−3.8+4.2 15 . 0 − 3.8 + 4.2 $ 15.0^{+4.2}_{-3.8} $ , 7.5−5.7+4.6 7 . 5 − 5.7 + 4.6 $ 7.5^{+4.6}_{-5.7} $ , 7.3−4.4+2.8 7 . 3 − 4.4 + 2.8 $ 7.3^{+2.8}_{-4.4} $ , and 3.0−3.7+5.3 3 . 0 − 3.7 + 5.3 $ 3.0^{+5.3}_{-3.7} $ light days with respect to the optical continuum at 4570 Å. The variability amplitudes of the integrated emission lines are a function of distance to the ionizing continuum source as well. We derived a central black hole mass of 3.8 ± 3.1 × 107 M⊙ based on the linewidths and distances of the BLR. The outer line wings of all BLR lines respond much faster to continuum variations indicating a Keplerian disk component for the BLR. The response in the outer wings is about two light days shorter than the response of the adjacent continuum flux with respect to the ionizing continuum flux. The vertical BLR structure in HE 1136-2304 confirms a general trend that the emission lines of narrow line active galactic nuclei (AGNs) originate at larger distances from the midplane in comparison to AGNs showing broader emission lines. Otherwise, the variability behavior of this changing look AGN is similar to that of other AGN.
Aims. To understand the nature of transient obscuring outflows in active galactic nuclei, we use simultaneous multiwavelength observations with XMM-Newton, NuSTAR, the Hubble Space Telescope (HST), ...and the Max Planck Gesellschaft/European Southern Observatory (ESO) 2.2 m telescope triggered by soft X-ray absorption detected by Swift. Methods. We obtained ultraviolet spectra on 2016-12-12 and 2016-12-21 using the Cosmic Origins Spectrograph (COS) on HST simultaneously with X-ray spectra obtained with XMM-Newton and NuSTAR. We modeled the ultraviolet spectra to measure the strength and variability of the absorption, and used photoionization models to obtain its physical characteristics. Results. We find new components of broad, blue-shifted absorption associated with Lyα, N V, Si IV, and C IV in our COS spectra. The absorption extends from near-zero velocities in the rest-frame of the host galaxy to −6200 km s−1. These features appear for the first time in NGC 3783 at the same time as heavy soft X-ray absorption seen in the XMM-Newton X-ray spectra. The X-ray absorption has a column density of ∼1023 cm−2, and it partially covers the X-ray continuum source. Combining the X-ray column densities with the UV spectral observations yields an ionization parameter for the obscuring gas of log ξ = 1.84−0.2+0.4 erg cm s−1 log ξ = 1 . 84 − 0.2 + 0.4 erg cm s −1 $ \log \xi = 1.84_{ - 0.2}^{ + 0.4}{\rm{erg}}\,{\rm{cm}}\,{{\rm{s}}^{ - 1}}\ $ . Despite the high intensity of the UV continuum in NGC 3783, F(1470 Å) = 8 × 10−14 erg cm−2 s−1 Å−1>, the well known narrow UV absorption lines are deeper than in earlier observations in unobscured states, and low ionization states such as C III appear, indicating that the narrow-line gas is more distant from the nucleus and is being shadowed by the gas producing the obscuration. Despite the high continuum flux levels in our observations of NGC 3783, moderate velocities in the UV broad line profiles have substantially diminished. Conclusions.We suggest that a collapse of the broad line region has led to the outburst and triggered the obscuring event.
We present the results from a detailed analysis of photometric and spectrophotometric data on five Seyfert 1 galaxies observed as a part of a recent reverberation mapping program. The data were ...collected at several observatories over a 140 day span beginning in 2010 August and ending in 2011 January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501, 3C 120, Mrk 6, and PG 2130+099, from which we have measured the time lag between variations in the 5100 Angstrom continuum and the H beta broad emission line. We then used these measurements to calculate the mass of the supermassive black hole at the center of each of these galaxies. Our new measurements substantially improve previous measurements of M sub(BH) and the size of the broad line-emitting region for four sources and add a measurement for one new object. Our new measurements are consistent with photoionization physics regulating the location of the broad line region in active galactic nuclei.
Aims.
We aim to reveal the sizes of the continuum and broad emission line (BEL) emitting regions in the gravitationally lensed quasar SDSS J1004+4112 by analyzing the unique signatures of ...microlensing in this system. Through a comprehensive analysis of 20 spectroscopic observations acquired between 2003 and 2018, we studied the striking deformations of various BEL profiles and determined the sizes of their respective emitting regions.
Methods.
Our approach involves a detailed analysis of the magnitude differences in the BEL wings and their adjacent continua, and the implementation of a statistical model to quantify the distribution and impact of microlensing magnifications. To ensure a reliable baseline for no microlensing, we used the emission line cores as a reference. We then applied a Bayesian estimate to derive the size lower limits of the Ly
α
, Si IV, C IV, C III, and Mg II emitting regions, as well as the sizes of the underlying continuum-emitting sources.
Results.
We analyzed the outstanding microlensing-induced distortions in the line profiles of various BELs in the quasar image A, characterized by a prominent magnification of the blue part and a strong demagnification of the red part. From the statistics of microlensing magnifications and using Bayesian methods, we estimate the lower limit to the overall size of the regions emitting the BELs to be a few light-days across, which is significantly smaller than in typically lensed quasars. The asymmetric deformations in the BELs indicate that the broad-line region is generally not spherically symmetric, and is likely confined to a plane and following the motions of the accretion disk. Additionally, the inferred continuum-emitting region sizes are larger than predictions based on standard thin-disk theory by a factor of ∼3.6 on average. The size-wavelength relation is consistent with that of a geometrically thin and optically thick accretion disk.
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