arXiv subjects

Ying-Ke Huang

Publications and source records attributed to Ying-Ke Huang.

At least 19 recordsLinked to original sources

arXiv2026

Beyond the EPICS: comprehensive Python IOC development with QueueIOC

Background and Purpose: Architectural deficiencies in EPICS lead to inefficiency in the development and application of EPICS IOCs. An unintrusive solution is replacing EPICS IOCs with more maintainable and flexible Python IOCs, only reusing the CA protocol of EPICS. While there are libraries like caproto and PCASPy that help to create Python IOCs, they still feel insufficient for more complex requirements. Methods: Noticing caput, caget and camonitor are just specialised combinations of requests/replies and notifications in client-server communication, by combining barebone caproto and event loops like those in server-like programs, the QueueIOC framework for Python IOCs is created, which has the potential to systematically reduce the development and maintenance cost of IOCs. Results: Examples based on QueueIOC are first given for workalikes of StreamDevice and asyn; also given are examples for "sequencer" applications, like those based on seq, include monochromators, motor anti-bumping and motor multiplexing. A QueueIOC-based framework for detector integration is presented in an accompanying paper. Also reported is a simple but expressive architecture for GUIs, as well as software to use with the ~/iocBoot convention which addresses some issues we find with a similar solution based on procServ.

physics.ins-det↗

arXiv2022

Supermassive Black Hole and Broad-line Region in NGC~5548: Results from Five-season Reverberation Mapping

NGC 5548 is one of the active galactic nuclei (AGN) selected for our long-term spectroscopic monitoring with the Lijiang 2.4~m telescope, aiming at investigating the origin and evolution of the broad-line regions (BLRs), accurately measuring the mass of the supermassive black holes (SMBHs), and understanding structure and evolution of the AGN. We have performed five-season observations for NGC~5548 with the median sampling interval ranging from 1.25 to 3 days. The light curves of the 5100~Å continuum and broad emission lines are measured after subtracting contamination of the host galaxy starlight. The time lags of the broad He~{\sc ii}, He~{\sc i}, H$γ$, and H$β$ lines with respect to the 5100~Å continuum are obtained for each season and their mean time lags over the five seasons are 0.69, 4.66, 4.60, 8.43 days, respectively. The H$γ$ and H$β$ velocity-resolved lag profiles in the seasons of 2015, 2018, 2019, and 2021 are constructed, from which an ``M-shaped'' structure is found in 2015 but disappears after 2018. Our five-season reverberation mapping (RM) yields an averaged virial SMBH mass of $M_\bullet/10^7M_\odot=14.22$, with a small standard deviation of $1.89$. By combining the previous 18 RM campaigns and our five-season campaign for NGC~5548, we find that there exists a time lag of 3.5~years between the changes in the BLR size and optical luminosity. In addition, we also construct the BLR radius$-$luminosity relation and the virial relation for NGC~5548.

astro-ph.GA↗

arXiv2022

Velocity-resolved Reverberation Mapping of Changing-look Active Galactic Nucleus NGC~4151 During Outburst Stage: Evidence for Kinematics Evolution of Broad-line Region

Changing-look active galactic nucleus NGC~4151, which has attracted a lot of attention, is undergoing the second dramatic outburst stage in its evolutionary history. To investigate the geometry and kinematics of the broad-line region (BLR), and measure the mass of supermassive black hole in NGC~4151, we perform a seven-month photometric and spectroscopic monitoring program in 2020--2021, using the 2.4 m telescope at Lijiang Observatory. We successfully measure the time lags of the responses from broad \ha, \hb, \hg, \hei, and \heii\ emission lines to continuum variation, which are $7.63_{-2.62}^{+1.85}$, $6.21_{-1.13}^{+1.41}$, $5.67_{-1.94}^{+1.65}$, $1.59_{-1.11}^{+0.86}$, and $0.46_{-1.06}^{+1.22}$ days, respectively, following radial stratification. The ratios of time lags among these lines are $1.23 : 1.00 : 0.91 : 0.26 : 0.07$. We find that the continuum lag between the ultraviolet and optical bands can significantly affect the lag measurements of \hei\ and \heii. Virial and infalling gas motions coexist in this campaign, which is different from previous results, implying the evolutionary kinematics of BLR. Based on our measurements and previous ones in the literature, we confirm that the BLR of NGC~4151 is basically virialized. Finally, we compute the black hole mass through multiple lines, and the measurement from \hb\ to be $ 3.94_{-0.72}^{+0.90} \times 10^7 M_{\odot}$, which is consistent with previous results. The corresponding accretion rate is $0.02_{-0.01}^{+0.01} L_{\rm Edd} c^{-2}$, implying a sub-Eddington accretor.

astro-ph.GA↗

arXiv2021

Application of the space-based optical interferometer towards measuring cosmological distances of quasars

Measuring the quasar distance through joint analysis of spectroastrometry (SA) and reverberation mapping (RM) observations is a new method for driving the development of cosmology. In this paper, we carry out detailed simulation and analysis to study the effect of four basic observational parameters (baseline length, exposure time, equivalent diameter and spectral resolution) on the data quality of differential phase curves (DPCs), furthermore on the accuracy of distance measurement. In our simulation, we adopt an axis symmetrical disc model of broad line region (BLR) to generate differential phase signals. We find that the differential phases and their Poisson errors could be amplified by extending the baseline, while the influence of OPD (optical path difference) errors can be reduced during fitting the BLR model. Longer exposure time or larger equivalent diameter helps reduce the absolute Poisson error. Therefore, the relative error of DPCs could be reduce by increasing any of the above three parameters, then the accuracy of distance measurement could be improved. In contrast, the uncertainty of $D_{\rm{A}}$ ( absolute angular distances) could be improved with higher spectral resolution, although the relative error of DPCs would be amplified. We show how the uncertainty of distance measurement varies with the relative error of DPCs. For our specific set of model parameters, without considering more complicated structures and kinematics of BLRs in our simulation, it is found that the relative error of DPCs $<$ 20$\%$ is a limit for accurate distance measurement. The relative error of DPCs have a lower limit (roughly 5$\%$) and the uncertainty of distance measurement can be better than 2$\%$.

astro-ph.HE↗

arXiv2021

Reverberation Mapping Measurements of Black Hole Masses and Broad-Line Region Kinematics in Mrk 817 and NGC 7469

We present the results from a spectroscopic monitoring campaign to obtain reverberation-mapping measurements and investigate the broad-line region kinematics for active galactic nuclei (AGN) of Mrk~817 and NGC~7469. This campaign was undertaken with the Lijiang 2.4-meter telescope, the median spectroscopic sampling is 2.0 days for Mrk~817 and 1.0 days for NGC~7469. We detect time lags of the broad emission lines including H$β$, H$γ$, He~{\sc ii} and He~{\sc i} for both AGNs, and including Fe~{\sc ii} for Mrk~817 with respect to the varying AGN continuum at 5100~Å. Investigating the relationship between line widths and time lags of the broad emission lines, we find that the BLR dynamics of Mrk~817 and NGC~7469 are consistent with the virial prediction. We estimate the masses of central supermassive black hole (SMBH) and the accretion rates of both AGNs. Using the data of this campaign, we construct the velocity-resolved lag profiles of the broad H$γ$, H$β$, and He~{\sc i} lines for Mrk~817, which show almost the same kinematic signatures that the time lags in the red wing are slightly larger than the time lags in the blue wing. For NGC~7469, we only clearly construct the velocity-resolved lag profiles of the broad H$γ$ and H$β$, which show very similar kinematic signatures to the BLR of Mrk~817. These signatures indicate that the BLR of Keplerian motion in both AGNs seemingly has outflowing components during the monitoring period. We discuss the kinematics of the BLR and the measurements including SMBH mass and accretion rates.

astro-ph.GA↗

arXiv2021

A correction method for the telluric absorptions and application to Lijiang Observatory

Observing a telluric standard star for correcting the telluric absorption lines of spectrum will take a significant amount of precious telescope time, especially in the long-term spectral monitoring project. Beyond that, it's difficult to select a suitable telluric standard star near in both time and airmass to the scientific object. In this paper, we present a method of correcting the telluric absorption lines by combining the advantages of long slit spectroscopy. By rotating the slit, we observed the scientific object and a nearby comparison star in one exposure, so that the spectra of both objects should have the same telluric transmission spectrum. The telluric transmission spectrum was constructed by dividing the observed spectrum of comparison star by its stellar template, and was used to correct the telluric absorption lines of the scientific object. Using the long slit spectrograph of Lijiang 2.4-meter telescope, we designed a long-term spectroscopic observation strategy, and finished a four-year spectroscopic monitoring for a pair of objects (an active galactic nuclei and an non-varying comparison star). We applied this method to correct the telluric absorption lines of the long-term monitored spectra by Lijiang 2.4-meter telescope, and investigated the variation of the telluric absorptions at Lijiang Observatory. We found that the telluric absorption transparency is mainly modulated by the seasonal variability of the relative humidity, airmass and seeing. Using the scatter of the [O~III] $λ$5007 fluxes emitted from the narrow-line region of active galactic nuclei as an indicator, we found that the correction accuracy of the telluric absorption lines is 1%.

astro-ph.IM↗

arXiv2020

Broad-line Region of the Quasar PG 2130+099 from a Two-Year Reverberation Mapping Campaign with High Cadence

As one of the most interesting Seyfert 1 galaxies, PG 2130+099 has been the target of several reverberation mapping (RM) campaigns over the years. However, its measured broad H$β$ line responses have been inconsistent, with time lags of $\sim$200 days, $\sim$25 days, and $\sim$10 days being reported for different epochs while its optical luminosity changed no more than 40%. To investigate this issue, we conducted a new RM-campaign with homogenous and high cadence (about $\sim$3 days) for two years during 2017--2019 to measure the kinematics and structure of the ionized gas. We successfully detected time lags of broad H$β$, He II, He I, and Fe II lines with respect to the varying 5100Åcontinuum, revealing a stratified structure that is likely virialized with Keplerian kinematics in the first year of observations, but an inflow kinematics of the broad-line region from the second year. With a central black hole mass of $0.97_{-0.18}^{+0.15}\times 10^7~M_{\odot}$, PG 2130+099 has an accretion rate of $10^{2.1\pm0.5}L_{\rm Edd}c^{-2}$, where $L_{\rm Edd}$ is the Eddington luminosity and $c$ is speed of light, implying that it is a super-Eddington accretor and likely possesses a slim, rather than thin, accretion disk. The fast changes of the ionization structures of the three broad lines remain puzzling.

astro-ph.GA↗

arXiv2019

A Possible ~20 yr Periodicity in Long-term Optical Photometric and Spectral Variations of the Nearby Radio-Quiet Active Galactic Nucleus Ark 120

We study the long-term variability in the optical monitoring database of Ark~120, a nearby radio-quiet active galactic nucleus (AGN) at a distance of 143 Mpc (z=0.03271). We compiled the historical archival photometric and spectroscopic data since 1974 and conducted a new two-year monitoring campaign in 2015-2017, resulting in a total temporal baseline over four decades. The long-term variations in the optical continuum exhibit a wave-like pattern and the Hbeta integrated flux series varies with a similar behavior. The broad Hbeta profiles have asymmetric double peaks, which change strongly with time and tend to merge into a single peak during some epochs. The period in the optical continuum determined from various period-search methods is about 20 yr and the estimated false alarm probability with null hypothesis simulations is about 1*10^-3. The overall variations of the broad Hbeta profiles also follow the same period. However, the present database only covers two cycles of the suggested period, which strongly encourages continued monitoring to track more cycles and confirm the periodicity. Nevertheless, in light of the possible periodicity and the complicated Hbeta profile, Ark~120 is one candidate of the nearest radio-quiet AGNs with possible periodic variability, and it is thereby a potential candidate host for a sub-parsec supermassive black hole binary.

astro-ph.HE↗

arXiv2019

Supermassive black holes with high accretion rates in active galactic nuclei: X. Optical variability characteristics

We compiled a sample of 73 active galactic nuclei (AGNs) with reverberation mapping (RM) observations from RM campaigns including our ongoing campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs). This sample covers a large range of black hole (BH) mass $(M_{\bullet}=10^{6-9}~M_\odot)$, dimensionless accretion rates $(\dot{\mathscr{M}}=10^{-2.7}-10^{2.7})$ and 5100~Å~luminosity $(L_{5100}=10^{42-46}~\rm erg~s^{-1})$, allowing us to systematically study the AGN variability and their relations with BH mass, accretion rates, and optical luminosity. We employed the damped random walk (DRW) model to delineate the optical variability of continuum at 5100~Å~and obtained damped variability timescale ($τ_{\rm d}$) and amplitude ($σ_{\rm d}$) using a Markov Chain Monte Carlo (MCMC) method. We also estimated the traditional variability amplitudes ($F_{\rm var}$), which provide a model-independent measure and therefore are used to test the DRW results. We found that AGN variability characteristics are generally correlated with $(M_{\bullet},\dot{\mathscr{M}},L_{5100})$. These correlations are smooth from sub-Eddington to super-Eddington accretion AGNs, probably implying that the AGN variability may be caused by the same physical mechanism.

astro-ph.GA↗

arXiv2019

Reverberation mapping of narrow-line Seyfert 1 galaxy I Zwicky 1: black hole mass

We report results of the first reverberation mapping campaign of I Zwicky 1 during $2014$-$2016$, which showed unambiguous reverberations of the broad H$β$ line emission to the varying optical continuum. From analysis using several methods, we obtain a reverberation lag of $τ_{\rm Hβ}=37.2^{+4.5}_{-4.9}\,$ days. Taking a virial factor of $f_{_{\rm BLR}}=1$, we find a black hole mass of $M_{\bullet}=9.30_{-1.38}^{+1.26}\times 10^6 M_{\odot}$ from the mean spectra. The accretion rate is estimated to be $203.9_{-65.8}^{+61.0}\,L_{\rm Edd}c^{-2}$, suggesting a super-Eddington accretor, where $L_{\rm Edd}$ is the Eddington luminosity and $c$ is the speed of light. By decomposing {\it Hubble Space Telescope} images, we find that the stellar mass of the bulge of its host galaxy is $\log (M_{\rm bulge}/M_{\odot}) = \rm 10.92\pm 0.07$. This leads to a black hole to bulge mass ratio of $\sim 10^{-4}$, which is significantly smaller than that of classical bulges and elliptical galaxies. After subtracting the host contamination from the observed luminosity, we find that I Zw 1 follows the empirical $R_{\rm BLR}\propto L_{5100}^{1/2}$ relation.

astro-ph.GA↗

arXiv2019

Kinematics of the Broad-line Region of 3C 273 from a Ten-year Reverberation Mapping Campaign

Despite many decades of study, the kinematics of the broad-line region of 3C~273 are still poorly understood. We report a new, high signal-to-noise, reverberation mapping campaign carried out from November 2008 to March 2018 that allows the determination of time lags between emission lines and the variable continuum with high precision. The time lag of variations in H$β$ relative to those of the 5100 Angstrom continuum is $146.8_{-12.1}^{+8.3}$ days in the rest frame, which agrees very well with the Paschen-$α$ region measured by the GRAVITY at The Very Large Telescope Interferometer. The time lag of the H$γ$ emission line is found to be nearly the same as for H$β$. The lag of the Fe II emission is $322.0_{-57.9}^{+55.5}$ days, longer by a factor of $\sim$2 than that of the Balmer lines. The velocity-resolved lag measurements of the H$β$ line show a complex structure which can be possibly explained by a rotation-dominated disk with some inflowing radial velocity in the H$β$-emitting region. Taking the virial factor of $f_{\rm BLR} = 1.3$, we derive a BH mass of $M_{\bullet} = 4.1_{-0.4}^{+0.3} \times 10^8 M_{\odot}$ and an accretion rate of $9.3\,L_{\rm Edd}\,c^{-2}$ from the H$β$ line. The decomposition of its $HST$ images yields a host stellar mass of $M_* = 10^{11.3 \pm 0.7} M_\odot$, and a ratio of $M_{\bullet}/M_*\approx 2.0\times 10^{-3}$ in agreement with the Magorrian relation. In the near future, it is expected to compare the geometrically-thick BLR discovered by the GRAVITY in 3C 273 with its spatially-resolved torus in order to understand the potential connection between the BLR and the torus.

astro-ph.GA↗

arXiv2018

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. VIII. Structure of the Broad-Line Region and Mass of the Central Black Hole in Mrk 142

This is the eighth in a series of papers reporting on a large reverberation mapping campaign to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). We employ the recently developed dynamical modeling approach for broad-line regions (BLRs) based on the method of Pancoast et al. to analyze the reverberation mapping dataset of Mrk 142 observed in the first monitoring season. In this approach, continuum variations are reconstructed using a damped random walk process, and BLR structure is delineated using a flexible disk-like geometry, in which BLR clouds move around the central BH with Keplerian orbits or inflow/outflow motion. The approach also includes the possibilities of anisotropic emission of BLR clouds, non-linear response of the line emission to the continuum, and different long-term trends in the continuum and emission-line variations. We implement the approach in a Bayesian framework that is apt for parallel computation and use a Markov Chain Monte Carlo technique to recover the parameters and uncertainties for the modeling, including mass of the central BH. We apply three BLR models with different prescriptions of BLR clouds distributions and find that the best model for fitting the data of Mrk 142 is a two-zone BLR model, consistent with the theoretical BLR model surrounding slim accretion disks. The best model yields a BH mass of $\log (M_\bullet/M_\odot)=6.23_{-0.45}^{+0.26}$, resulting in a virial factor of $\log f=-0.36_{-0.54}^{+0.33}$ for the full width at half maximum of the H$β$ line measured from the mean spectrum. The virial factors for the other measures of the H$β$ line width are also presented.

astro-ph.GA↗

arXiv2018

A High-Quality velocity-delay map of the broad-line region in NGC 5548

NGC 5548 has been well spectroscopically monitored for reverberation mapping of the central kinematics by 19 campaigns. Using the maximum entropy method in this Letter, we build up a high-quality velocity-delay map of the H$β$ emission line in the light curves of the continuum and the line variations observed between 2015-2016. The map shows the response strength and lags of the velocity fields of the H$β$ emitting regions. The velocity-delay structure of the map is generally symmetric, with strong red and blue wings at time lag $τ\leq 15$ days, a narrower velocity distribution at $τ\geq 15$ days, and a deficit of response in the core. This is suggestive of a disk geometry of the broad-line region (BLR). The relatively weaker H$β$ response at the longer lags in the red side indicates anisotropic emission from the outer part of the BLR. We also recover the velocity-delay maps of NGC 5548 from the historical data of 13 years to investigate the long-term variability of its BLR. In general, the BLR of NGC 5548 was switching between the inflow and virialized phases in the past years. The resultant maps of seven years reveal inflow signatures and show decreasing lags, indicating that the changes in the BLR size are related to the infalling BLR gas. The other four maps show potential disk signatures which are similar to our map.

astro-ph.GA↗

arXiv2018

Supermassive black holes with high accretion rates in active galactic nuclei. VII. Reconstruction of velocity-delay maps by maximum entropy method

As one of the series of papers reporting on a large reverberation mapping campaign, we apply the maximum entropy method (MEM) to 9 narrow-line Seyfert 1 galaxies with super-Eddington accretion rates observed during 2012-2013 for the velocity-delay maps of their Hβ and Hγ emission lines. The maps of 6 objects are reliably reconstructed using MEM. The maps of Hβ and Hγ emission lines of Mrk 335 indicate that the gas of its broad-line region (BLR) is infalling. For Mrk 142, its Hβ and Hγ lines show signatures of outflow. The Hβ and Hγ maps of Mrk 1044 demonstrate complex kinematics -- a virialized motion accompanied by an outflow signature, and the Hβ map of IRAS F12397+3333 is consistent with a disk or a spherical shell. The Hβ maps of Mrk 486 and MCG +06-26-012 suggest the presence of an inflow and outflow, respectively. These super-Eddington accretors show diverse geometry and kinematics. Brief discussions of their BLRs are provided for each individual object.

astro-ph.GA↗

arXiv2018

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IX 10 New Observations of Reverberation Mapping and Shortened H$β$ Lags

As one of the series of papers reporting on a large reverberation mapping campaign of super-Eddington accreting massive black holes (SEAMBHs) in active galactic nuclei (AGNs), we present the results of 10 SEAMBHs monitored spectroscopically during 2015-2017. Six of them are observed for the first time, and have generally higher 5100 Å luminosities than the SEAMBHs monitored in our campaign from 2012 to 2015; the remaining four are repeat observations to check if their previous lags change. Similar to the previous SEAMBHs, the H$β$ time lags of the newly observed objects are shorter than the values predicted by the canonical $R_{\mathrm{Hβ}}$-$L_{5100}$ relation of sub-Eddington AGNs, by factors of $\sim2-6$, depending on the accretion rate. The four previously observed objects have lags consistent with previous measurements. We provide linear regressions for the $R_{\mathrm{Hβ}}$-$L_{5100}$ relation, solely for the SEAMBH sample and for low-accretion AGNs. We find that the relative strength of Fe II and the profile of the H$β$ emission line can be used as proxies of accretion rate, showing that the shortening of H$β$ lags depends on accretion rates. The recent SDSS-RM discovery of shortened H$β$ lags in AGNs with low accretion rates provides compelling evidence for retrograde accretion onto the black hole. These evidences show that the canonical $R_{\mathrm{Hβ}}$-$L_{5100}$ relation holds only in AGNs with moderate accretion rates. At low accretion rates, it should be revised to include the effects of black hole spin, whereas the accretion rate itself becomes a key factor in the regime of high accretion rates.

astro-ph.GA↗

arXiv2016

Reverberation Mapping of the Broad-line Region in NGC 5548: Evidence for Radiation Pressure?

NGC 5548 is the best-observed reverberation-mapped active galactic nucleus with long-term, intensive monitoring. Here we report results from a new observational campaign between January and July, 2015. We measure the centroid time lag of the broad H$β$ emission line with respect to the 5100 Åcontinuum and obtain $τ_{\rm cent} = 7.20^{+1.33}_{-0.35}$ days in the rest frame. This yields a black hole mass of $M_{\bullet}=8.71^{+3.21}_{-2.61} $x$ 10^{7}M_{\odot}$ using a broad H$β$ line dispersion of $3124\pm302$ km s$^{-1}$ and a virial factor of $f_{_{\rm BLR}}=6.3\pm1.5$ for the broad-line region (BLR), consistent with the mass measurements from previous H$β$ campaigns. The high-quality data allow us to construct a velocity-binned delay map for the broad H$β$ line, which shows a symmetric response pattern around the line center, a plausible kinematic signature of virialized motion of the BLR. Combining all the available measurements of H$β$ time lags and the associated mean 5100 Å luminosities over 18 campaigns between 1989 and 2015, we find that the H$β$ BLR size varies with the mean optical luminosity, but, interestingly, with a possible delay of $2.35_{-1.25}^{+3.47}$ yrs. This delay coincides with the typical BLR dynamical timescale of NGC 5548, indicating that the BLR undergoes dynamical changes, possibly driven by radiation pressure.

astro-ph.GA↗

arXiv2016

Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. V. A New Size-Luminosity Scaling Relation for the Broad-Line Region

This paper reports results of the third-year campaign of monitoring super-Eddington accreting massive black holes (SEAMBHs) in active galactic nuclei (AGNs) between 2014-2015. Ten new targets were selected from quasar sample of Sloan Digital Sky Survey (SDSS), which are generally more luminous than the SEAMBH candidates in last two years. H$β$ lags ($τ_{_{\rm Hβ}}$) in five of the 10 quasars have been successfully measured in this monitoring season. We find that the lags are generally shorter, by large factors, than those of objects with same optical luminosity, in light of the well-known $R_{_{\rm Hβ}}-L_{5100}$ relation. The five quasars have dimensionless accretion rates of $\dot{\mathscr{M}}=10-10^3$. Combining measurements of the previous SEAMBHs, we find that the reduction of H$β$ lags tightly depends on accretion rates, $τ_{_{\rm Hβ}}/τ_{_{R-L}}\propto\dot{\mathscr{M}}^{-0.42}$, where $τ_{_{R-L}}$ is the H$β$ lag from the normal $R_{_{\rm Hβ}}-L_{5100}$ relation. Fitting 63 mapped AGNs, we present a new scaling relation for the broad-line region: $R_{_{\rm Hβ}}=α_1\ell_{44}^{β_1}\,\min\left[1,\left(\dot{\mathscr{M}}/\dot{\mathscr{M}}_c\right)^{-γ_1}\right]$, where $\ell_{44}=L_{5100}/10^{44}\,\rm erg~s^{-1}$ is 5100 Å continuum luminosity, and coefficients of $α_1=(29.6_{-2.8}^{+2.7})$ lt-d, $β_1=0.56_{-0.03}^{+0.03}$, $γ_1=0.52_{-0.16}^{+0.33}$ and $\dot{\mathscr{M}}_c=11.19_{-6.22}^{+2.29}$. This relation is applicable to AGNs over a wide range of accretion rates, from $10^{-3}$ to $10^3$. Implications of this new relation are briefly discussed.

astro-ph.GA↗

arXiv2016

Spectroscopic Indication for a Centi-parsec Supermassive Black Hole Binary in the Galactic Center of NGC 5548

As a natural consequence of cosmological hierarchical structure formation, sub-parsec supermassive black hole binaries (SMBHBs) should be common in galaxies but thus far have eluded spectroscopic identification. Based on four decades of optical spectroscopic monitoring, we report that the nucleus of NGC 5548, a nearby Seyfert galaxy long suspected to have experienced a major merger about one billion years ago, exhibits long-term variability with a period of 14 years in the optical continuum and broad Hbeta emission line. Remarkably, the double-peaked profile of Hbeta shows systematic velocity changes with a similar period. These pieces of observations plausibly indicate that a SMBHB resides in the center of NGC 5548. The complex, secular variations in the line profiles can be explained by orbital motion of a binary with equal mass and a semi-major axis of 22 light-days (corresponding to 18 milli-parsec). At a distance of 75 Mpc, NGC 5548 is one of the nearest sub-parsec SMBHB candidates that offers an ideal laboratory for gravitational wave detection.

astro-ph.GA↗