A Possible X-ray Quasi-periodic Oscillation in the Narrow-line Seyfert 1 Galaxy Mrk 142

A possible quasi-periodic oscillation(QPO) at frequency 7.045 × 10^(-5) Hz is found in the narrow-line Seyfert 1galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11.We find that the QPO signal is statistically significantly larger than the 5σ level and highly coherent with quality factor Q > 5 at the 0.3–10 keV band by using the method of the Lomb–Scargle Periodogram,the Weighted Wavelet Z-transform and the REDFIT.We analyze the data in 0.3–0.6 keV,0.6–1 keV,1–3 keV and 3–10 keV energy bands,and find obvious QPO signals at 0.3–0.6 keV and 1–3 keV bands.We then analyze the time-average spectra and time variability at the QPO frequency of 7.045 × 10^(-5) Hz,and use a model to fit them.We find that the QPO signal mainly comes from the X-ray hot corona.

Long Term X-Ray Spectral Variations of the Seyfert-1 Galaxy Mrk 279

We present the results from a long term X-ray analysis of Mrk 279 during the period 2018–2020.We use data from multiple missions–AstroSat,NuSTAR and XMM-Newton,for the purpose.The X-ray spectrum can be modeled as a double Comptonization along with the presence of neutral Fe Kαline emission,at all epochs.We determined the source’s X-ray flux and luminosity at these different epochs.We find significant variations in the source’s flux state.We also investigate the variations in the source’s spectral components during the observation period.We find that the photon index and hence the spectral shape follow the variations only over longer time periods.We probe the correlations between fluxes of different bands and their photon indices,and found no significant correlations between the parameters.

UV and X-ray variability of the narrow-line Seyfert 1 galaxy Ark 564

We analyze eight XMM-Newton observations of the bright Narrow Line Seyfert 1 galaxy Arakelian 564（Ark 564）. These observations, separated bye^6 days, allow us to look for correlations between the simultaneous ultraviolet（UV） emission（from th Optical Monitor） with not only the X-ray flux but also with different X-ray spectral parameters. The X-ray spectra from all the observations are found to be adequately fitted by a double Comptonization model where the soft excess and the hard X-ray power law are represented by thermal Comptonization in a low temperature plasma and hot corona, respectively. Apart from the fluxes of each component, the hard X-ray power law index is found to be variable. These results suggest that the variability is associated with changes in the geometry of the inner region. The UV emission is found to be variable and well correlated with the high energy index while the correlations with the fluxes of each component are found to be weaker. Using viscous timescale arguments we rule out the possibility that the UV variation is due to the fluctuating accretion rate in the outer disk. If the UV variation is driven by X-ray reprocessing, then our results indicate that the strength of the X-ray reprocessing depends more on the geometry of the X-ray producing inner region rather than on the X-ray luminosity alone.

The inner～40 pc radial distribution of the star formation rate for a nearby Seyfert 2 galaxy M51

We investigate the spatially resolved specific star formation rate （SSFR） in the inner -40 pc for a nearby Seyfert 2 galaxy, M51 （NGC 5194） by analyzing spectra obtained with the Hubble Space Telescope （HST） Space Telescope Imaging Spectrograph （STIS）. We present 24 radial spectra measured along the STIS long slit in M51, extending - 1＂ from the nucleus （i.e., -41.5 pc to 39.4 pc）. By simple stellar population synthesis, the stellar contributions in these radial optical spectra are modeled. It is found that the mean flux fraction of young stellar populations （younger than 24.5 Myr） is about 9%. Excluding some regions with zero young flux fraction near the center （from -6 pc to 2 pc）, the mean mass fraction is about 0.09%. The young stellar populations are not required in the center inner -8 pc in M51, suggesting a possible SSFR suppression in the circumnuclear region （- 10 pc） from the feedback of active galactic nuclei （AGNs）. The radial distribution of SSFR in M51 is not symmetrical with respect to the long slit in STIS. This unsymmetrical SSFR distribution is possibly due to the unsymmetrical AGN feedback in M51, which is related to its jet.

Serendipitous discovery of warm absorbers in the Seyfert 2 galaxy IRAS 18325-5926

Warm absorption is a common phenomenon in Seyfert 1 s and quasars, but is rare in Seyfert 2s. We report the detection of warm absorbers with high energy resolution in the Seyfert 2 galaxy IRAS 18325-5926 for the first time with Chandra HETGS spectra. An intrinsic absorbing line system with an outflow velocity - 400 km s^-1 was found, which is contributed by two warm absorbers with FWHM of 570 km s^-1 and 1360 km s^-1, respectively. The two absorbers were adjacent, and moving transversely across our line of sight. We constrained the distance between the center and the absorbers to be a small value, suggesting that the absorbers may originate from the highly ionized accretion disk wind ejected five years ago. The perspective of this type 2 Seyfert provides the best situation in which to investigate the vertical part of the funnel-like outflows. Another weak absorbing line system with zero redshift was also detected, which could be due to Galactic absorption with very high temperature or an intrinsic outflow with a very high velocity - 6000 km s^-1.

Multicolor Optical Monitoring of the γ-Ray Emitting Narrow-line Seyfert 1 Galaxy PMN J0948+0022 from 2020 to 2021

In order to study the physical properties of the γ-ray emitting narrow-line Seyfert 1(NLS1) galaxy population,photometric and spectral observations of the γ-ray emitting NLS1 PMN J0948+0022 were made with the Lijiang2.4 m optical telescope of Yunnan Observatories,Chinese Academy of Sciences.Photometric data in the B and R bands were collected for 50 nights from 2020 January to 2021 December.During the observation epoch,the variability amplitudes are 73.67% in the B band and 79.96% in the R band.Intra-day variability is found in two observation nights,and the duty cycle value is 29% with variability amplitude> 12.9% in the R band,which support the presence of the relativistic jets in the target.The redder-when-brighter(RWB) chromatic trend(or steeper-when-brighter trend) appears on intra-day and long timescales.The RWB trend is dominated by the radiation of accretion disk and jet,and resembles those in flat spectrum radio quasars.When PMN J0948+0022 is brighter than 17.5 in the R band,there is no color change trend.By analyzing the spectral data of PMN J0948+0022,we obtained the black hole mass of M.=1.61×10^(7) Mand accretion rate of M=93,and confirmed that PMN J0948+0022 is a super-Eddington accreting NLS1.The redshifts of reverberation mapped super-Eddington accreting active galactic nuclei can be expanded by PMN J0948+0022 up to above 0.5.Super-Eddington accreting NLS1 galaxies were chosen as a new type of cosmological candle in the literature.PMN J0948+0022 may be used as a target for the next step of reverberation mapping monitoring project of super-Eddington accreting massive black holes.

Nuclear Starburst Activity in the Seyfert 2 Galaxy NGC 2273

We present spectrophotometric results of the Seyfert 2 galaxy NGC 2273. Thepresence of high-order Balmer absorption lines (H8, H9, H10) and weak equivalent widths of CaII Kλ3933, CN λ4200, G-band λ4300 and MgIb λ5173 clearly indicate recent star-forming activity inthe nuclear region. Using a simple stellar population synthesis model, we find that for the bestfit, the contributions of a power-law featureless continuum, an intermediate-age (～ 10~8 yr) and anold (> 10~9 yr) stellar population to the total light at the reference normalization wavelength are10.0%, 33.4% and 56.6%, respectively. The existence of recent starburst activity is also consistentwith its high far-infrared luminosity (log L_(FIR.)/L☉ = 9.9), its infrared color indexes[α(25,60) = ― 1.81 and α(60,100) = ― 0.79, typical values for Seyfert galaxies withcircumnuclear starburst], and its q-value (2.23, ratio of infrared to radio flux, very similar tothat of normal spirals and starburst galaxies). Byrd et al. have suggested that NGC 2273 might haveinteracted with NGC 2273B in less than 10~9 yr ago, so the starburst activity in this galaxy couldhave been triggered by tidal interaction, as indicated in recent numerical simulations.

The Origin of The Soft X-Ray Excess in the Seyfert 1.5 Galaxy ESO 362-G18

We review the Seyfert 1.5 Galaxy ESO 362-G18 for exploring the origin of the soft X-ray excess.The Warm Corona and Relativistic Reflection models are two main scenarios to interpret the soft X-ray excess in active galactic nuclei at present.We use the simultaneous X-ray observation data of XMM-Newton and Nu STAR on2016 September 24 to perform spectral analysis in two steps.First,we analyze the time-average spectra by using Warm Corona and Relativistic Reflection models.Moreover,we also explore the Hybrid model,Double Reflection model and Double Warm Corona model.We find that both the Warm Corona and Relativistic Reflection models can interpret the time-average spectra well but cannot be distinguished easily based on the time-averaged spectra fit statistics.Second,we add the rms and covariance spectra to perform the spectral analysis with time-average spectra.The result shows that the warm corona could reproduce all of these spectra well.The hot,optical thin corona and neutral distant reflection will increase their contribution with the temporal frequency,meaning that the corona responsible for X-ray continuum comes from the inner compact X-ray region and the neutral distant reflection is made of some moderate scale neutral clumps.

SDSS J022119.84+005628.4:A Radio-Loud Narrow-Line Seyfert 1 Galaxy with Star Formation in its Nucleus

The optical spectrum of SDSS J022119.84 + 005628.4 (R. A. = 02h 21m 19.84s, Dec = 00°56' 28.4', J2000; z = 0.399785 ± 0.000558) is analyzed by multi-component profile modelling. The small flux ratio of [OⅢ]NC/Hβ (=0.78) and FWHM(HβBC) = 1778.1 ±85.9 km s-1 led us to identify SDSS J022119.84 + 005628.4 as a Narrow-line Seyfert 1 galaxy with RFe= 1.4-1.0+1.0 and intermediate radio loudness, logR = 1.93. The continuum low jump at the Balmer limit might be contributed by a starburst component, which suggests that the object is a relatively young AGN with star-formation activity in its inner region. This provides a useful observational test of the AGN evolution. The low flux ratio of the narrow components, [OⅢ]/Hβ = 1.62, and the prominent [OⅡ]γ3727 emission, [OⅡ]/[OⅢ] = 2.24, suggests that there should be a group of AGNs different from Seyfert 2s when their broad line regions are obscured by the torus on the line of sight. A possible orientation effect is suggested to interpret the observed Seyfert 1.5s-like spectrum of the object. The spectrum features prominent broad blue wings of both [OⅢ]γγ4959 and 5007. After excluding other possible contributions, we conclude that the broad components are emitted by [O Ⅲ] itself. The material emitting the broad [O III] line is probably situated in a transient line region (with a low electron density, ne < 107cm-3) between the broad line region (BLR) and the narrow line region (NLR). The object can be classified as a 'blue outlier' defined by Zamanov et al., according to its velocity shift vr([OⅢ]) = -293.6 ± 18.0 km s-1, relative to the systematic velocity.

Chandra Observations of the Flat Spectrum Seyfert-2 Galaxies NGC 2110 and NGC 7582

Chandra observations of the Seyfert-2 galaxies NGC 2110 and NGC 7582 arepresented. With the superb spatial resolution of Chandra we found that in NGC 7582 the soft (≤2keV) and hard (2-10 keV) X-rays are emitted in different regions, consistent with the report by Xueet al. By comparing the present X-ray data with the previous infrared data, we determined that thesoft X-ray region is the site of starburst activities. We found no significant temporal variationsduring our observations. We confirm the previous finding that NGC 2110 and NGC 7582 areflat-spectrum sources. We argue that the flat spectra may result from a cold absorbing material suchas envisaged in the 'dual absorbed' model. Strong FeK_α emission feature is detected in 6～7keV.Its equivalent width is so large that it cannot be reproduced by using the Galactic column densityof ～ 10^(22) cm^(-2).

Are Seyfert 2 Galaxies without Polarized Broad Emission Lines More Obscured?

New XMM-Newton data of seven Seyfert 2 galaxies with optical spectropolarimetric observations are presented. An analysis of the 0.5 - 10 keV spectra shows that four Seyfert 2 galaxies with polarized broad lines （PBLs） are absorbed by NH 〈 1024 cm^-2, while two of three Seyfert 2 galaxies without PBLs show evidence of Compton-thick obscuration, supporting the conclusion that Seyfert 2 galaxies without PBLs are more obscured than those with PBLs, Adding the measured obscuration indicators （NH, T ratio, and Fe Kα line EW） of six luminous AGNs to our previous sample improves the significance level of the difference in absorption from 92.3% to 96.3% for NH, 99.1% to 99.4% for T ratio, and 95.3% to 97.4% for Fe Kα line EW. The present results support and enhance the suggestions that the absence of PBLs in Seyfert 2 galaxies can be explained by larger viewing angles of the line of sight to the putative dusty toms, which leads to the obscuration of the broad-line scattering screen, as expected in the unification model.

Similarity of jet radiation between flat spectrum radio quasars and GeV narrow-line Seyfert 1 galaxies: a universal δ-Lc correlation

By modeling the broadband spectral energy distributions （SEDs） of a typical flat spectrum radio quasar （FSRQ, 3C 279） and two GeV narrow-line Seyfert 1 galaxies （NLSls, PMN J0948＋0022 and 1H 0323＋342） in different flux stages with one-zone leptonic models, we find a universal correlation between their Doppler factors （δ） and peak luminosities （Lc） of external Compton scattering bumps. Compiling a combined sample of FSRQs and GeV NLSls, it is found that both FSRQs and GeV NLSls in different stages and in different sources follow the same δ-Lc correlation well. This indicates that the variations of observed luminosities may be essentially due to the Doppler boosting effect. The universal δ-Lo relation between FSRQs and GeV NLS 1 s in different stages may be further evidence that the particle acceleration and radiation mechanisms for the two kinds of sources are similar. In addition, by replacing Lc with the observed luminosity in the Fermi/LAT band （LLAT）, this correlation holds and it may serve as an empirical indicator of δ. We estimate the δ values with LLAT for 484 FSRQs in the Fermi/LAT Catalog and they range from 3 to 41, with a median of 16, which are statistically consistent with the values derived by other methods.

The Variability of the Narrow-line Seyfert 1 Galaxies from the Pan-STARRS's View

By means of the data sets from the Pan-STARRS1 survey, we have systematically examined the relationship between the variability characteristics and the physical parameters of the largest NLS1 galaxy sample up to now.The results are summarized as follows:(1). We find significant anti-correlations between variability amplitude and absolute magnitude in g, r, i, z and y bands, which are consistent with the results in previous works.(2) The correlations between the variability amplitude in optical band and many physical parameters(e.g., λL(5100 A),black hole mass, Eddington ratio, R;and R;) are investigated. The results show the variability amplitude is significantly anti-correlated with L(5100 A), MBH, Eddington ratio and R_(4570), but positively correlated with R;.The relation could be explained by the simple standard accretion disk model.(3) We further investigate the relationship between optical variability and radio luminosity/radio-loudness. The results present weak positive correlation in g and r bands, but insignificant correlation in i, z and y bands. The large error of the approximate fraction of the host galaxy in i, z and y bands may lead to insignificant correlations.

Jet Formation Mechanism of the Gamma-Ray-emitting Narrow-line Seyfert 1 Galaxies

We use a large sample of gamma-ray narrow-line Seyfert 1 galaxies(γ-NLS1 s) to study the jet formation mechanisms. We find that the jet power of γ-NLS1 s is lower than the maximum jet power of the Blandford–Payne(BP) mechanism. At the same time, we find that there is a significant correlation between jet power and accretion disk luminosity. Moreover, the contribution rates of the accretion to the jet power are larger than that of black hole mass to jet power. These results further suggest that the jet of γ NLS1 s is mainly produced by the BP mechanism.

Inclination of Broad Line Region in Narrow Line and Broad Line Seyfert 1 Galaxies

The sizes of the Broad Line Region (BLR) of some Seyfert 1 galaxies and nearby quasars can be determined by the reverberation mapping method. Combining with the observed FWHM of Hbeta emission line and assuming that the motion of BLR clouds is virialized, the black hole masses of these objects have been estimated. However, this method strongly depends on the poorly-understood geometry and inclination of the BLR. On the other hand, a tight correlation between the black hole mass and the bulge velocity dispersion was recently found for both active and nearby inactive galaxies. This may provide another method, independent of the BLR geometry, for estimating the black hole mass. Using this method for estimating the black hole mass and combining with the measured BLR size and FWHM of Hbeta emission line, we derived the BLR inclination angles for 20 Seyfert 1 galaxies under the assumption that the BLR is disk-like. The derived inclination angles agree well with those derived previously by fitting the UV continuum and Hbeta emission line profiles. Adopting a relation between the FWHMs of [OIII]lambda5007 forbidden line and the stellar velocity dispersion, we also estimated the BLR inclinations for 50 narrow line Seyfert 1 galaxies (NLS1s). We found that the inclinations of broad Line Seyfert 1 galaxies (BLS1s) axe systematically greater than those of NLS1s, which seldom exceed 30degrees. This may be an important factor that leads to the differences between NLS1s and BLS1s if the BLR of NLS1s is really disk-like.

Properties of Broad Band Continuum of Narrow Line Seyfert 1 Galaxies

We have performed a statistical study of the properties of the broad band continuum of Narrow Line Seyfert 1 galaxies (NLS1s) by collecting ratio, infrared, optical and X-ray continuum data from various databases and compared the results with control samples of Broad Line Seyfert 1 galaxies (BLS1s). We find that the fraction (similar to 6%) of Radio Loud (RL) NLS1s is significantly less than that of BLS1s (similar to 13%), which is caused by the lack of radio-very-loud sources in the former. The rarity of RL NLS1s, especially radio-very-loud ones, is consistent with the scenario of small black hole and high accretion rate for NLS1s. Six new radio loud NLS1s are found and five RL NLS1 candidates are presented. In comparison with the BLS1s, the NLS1s tend to have stronger far infrared emission, cooler infrared colors and redder B - K color, which suggests that NLS1s are hosted by dust-richer nuclei. The NLS1s also show steeper soft X-ray spectrum and large soft X-ray to optical flux ratio, while a significant fraction show flat soft X-ray spectra. At least two factors can account for this, absorption and spectral variability. We also perform a correlation analysis between various broad band data. It is found that most correlations identified for NLS1s are also valid for radio quiet BLS1s: (1) the optical colors are anti-correlated with X-ray spectral index; (2) higher optical, Xray and NIR luminosity objects show bluer optical colors and red H - K color; (3) higher luminosity objects show warmer IRAS color; (4) the radio loudness correlates with B - K and X-ray to optical flux ratio. Radio loud objects behave somewhat differently in a few correlations.

The Hybrid Nature of 0846+51W1: a BL Lac Object with a Narrow Line Seyfert 1 Nucleus

We found a NLS1 nucleus in the extensively studied eruptive BL Lac object, 0846+51W1, out of a large sample of NLS1s compiled from the spectroscopic dataset of SDSS DR1. Its optical spectrum can be well decomposed into three components: a power law component from the relativistic jet, a stellar component from the host galaxy, and a component from a typical NLS1 nucleus. The emission line properties of 0846+51W1, FWHM (Hβ) (?) 1710 km s-1 and [OⅢ]λ5007/Hβ(?)0.32 from its SDSS spectrum observed when it was in the faint state, fulfil the conventional definition of NLS1. Strong Fell emission is detected in the SDSS spectrum, which is also typical of NLS1s. We tried to estimate its central black hole mass using various techniques and found that 0846+51W1 is very likely emitting at a few ×10% of the Eddington luminosity. We speculate that Seyfert-like nuclei, including NLS1s, might be concealed in a significant fraction of BL Lacs but have remained largely unobserved because, often, their optical-UV continuum is overwhelmed by the synchrotron emission.

Comptonization and Reprocessing Processes in Accretion Disks: Applications to the Seyfert 1 Galaxies NGC 5548 and NGC 4051

Simultaneous multi-wavelength observations have revealed complex variability in AGNs. To explain the variability we considered a theoretical model consisting of an inner hot comptonizing corona and an outer thin accretion disk, with interactions between the two components in the form of comptonization and reprocessing. We found that the variability of AGNs is strongly affected by the parameters of the model, namely, the truncated disk radius rmin, the corona radius rs, the temperature KTe and the optical depth TO of the corona. We applied this model to the two best observed Seyfert 1 galaxies, NGC 5548 and NGC 4051. Our model can reproduce satisfactory the observed SEDs. Our fits indicate that NGC 5548 may have experienced dramatic changes in physical parameters between 1989-1990 and 1998, and that NGC 4051 has a much larger truncated disk radius （700 Schwarzschild radii） than NGC 5548 （several tens of Schwarzschild radii）. Since we adopted a more refined treatment of the comptonization process rather than simply assuming a cut-off power law, our results should be more reasonable than the previous ones.

Is There a Link Between Emission-Line Widths and X-Ray Continuum Slopes in Narrow Line Seyfert 1 Galaxies?

We present the discovery of 18 narrow line Seyfert 1 galaxies (NLS1). The optical spectra show the Balmer lines only slightly broader than the forbidden lines and contain strong Fe Ⅱ emission. No particularly soft X ray spectral slopes can be seen compared to a normal Seyfert 1 galaxies sample.

The Variability of Hardness Ratio 1 observed by ROSAT:Narrow-Line Seyfert 1 Galaxies versus Broad-Line Seyfert 1 Galaxies

We examined the correlation between the ROSAT Hardness Ratio 1 and Count Rates eight Narrow-line Seyfert 1 Galaxies (NLSls) and 14 Broad-line Seyfertl Galaxies (BLSls). We found that six of the NLSls show a positive HR1-CTs correlation, and seven of the BLSls, a negative correlation. The other two NLSls and seven BLSls do not show any clear HR1-CTs correlation. Thus, the spectral behavior is statistically different for the NLSls and BLSls. The different behaviors can possibly be interpreted in terms of a stable 'soft excess' that is strong in NLSls and weak in BLSls, plus a power law component, common to both, which softens with increasing flux.