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.

An Asymmetric Galactic Stellar Disk Traced by OB-type Stars from LAMOST DR7

Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angleΦ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around h_(s)=130 pc.The distribution of the displaceeent of the disk plane Z_(0)also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric.

Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

We present an efficient, robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies. With appropriate mathematical treatments, the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed. Using a boundary element discretization procedure, the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations. The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve （or vice versa）. For a disk galaxy with a typical flat rotation curve, our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery, according to Newtonian dynamics. In a large portion of the galaxy, the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate. Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution, suggesting an increasing mass-tolight ratio with the radial distance in a disk galaxy. In a nondimensionalized form, our mathematical system contains a dimensionless parameter which we call the ＂galactic rotation number＂ that represents the gross ratio of centrifugal force and gravitational force. The value of this galactic rotation number is determined as part of the numerial solution. Through a systematic computational analysis, we have illustrated that the galactic rotation number remains within 4-10% of 1.70 for a wide variety of rotation curves. This implies that the total mass in a disk galaxy is proportional to V02 Rg, with V0 denoting the characteristic rotation velocity （such as the ＂flat＂ value in a typical ro- tation curve） and Rg the radius of the galactic disk. The predicted total galactic mass of the Milky Way is in good agreement with the star-count data.

A Possible γ-Ray Pulsation from PSR J1740-5340B in the Globular Cluster NGC 6397

Recently, a new radio millisecond pulsar(MSP) J1740-5340B, hosted in the globular cluster(GC) NGC 6397,was reported with a 5.78 ms spin period in an eclipsing binary system with a 1.97 days orbital period. Based on a modified radio ephemeris updated by tool tempo2, we analyze the ~15 yr γ-ray data obtained from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope and detect PSR J1740-5340B's γ-ray pulsation at a confidence level of ~4σ with a weighted H-test value of ~26. By performing a phase-resolved analysis, the γ-ray luminosity in on-pulse interval of PSR J1740-5340B is L_(γ)~ 3.8 × 10^(33) erg s^(-1) using NGC 6397's distance of 2.48 kpc. And γ-rays from the on-pulse part of PSR J1740-5340B contribute ~90% of the total observed γ-ray emissions from NGC 6397. No significant γ-ray pulsation of another MSP J1740-5340A in the GC is detected.Considering that the previous four cases of MSPs in GCs, more data in γ-ray, X-ray, and radio are encouraged to finally confirm the γ-ray emissions from MSP J1740-5340B, especially starving for a precise ephemeris.

Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies

We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson＇s equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point （the forbidden region with radius r0 to the galactic center） of the spiral arm, and finally the thickness.

The Difference between the α-disks of Seyfert 1 Galaxies and Quasars

In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard a disk of AGNs. Using the nuclear absolute B band magnitude instead of the total absolute B band magnitude, we have recalculated the central black hole masses, accretion rates and disk inclinations for 20 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars. It is found that a small value of a is needed for the Seyfert 1 galaxies than for the PG quasars. This difference in a possibly leads to the different properties of Seyfert 1 galaxies and quasars. Furthermore, we find most of the objects in this sample are not accreting at super-Eddington rates if we adopt the nuclear optical luminosity in our calculation.

On the metallicity gradients of the Galactic disk as revealed by LSS-GAC red clump stars

Using a sample of over 70 000 red clump（RC） stars with 5%–10% distance accuracy selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center（LSS-GAC）, we study the radial and vertical gradients of the Galactic disk（s） mainly in the anti-center direction, covering a significant volume of the disk in the range of projected Galactocentric radius 7 ≤ RGC ≤ 14 kpc and height from the Galactic midplane 0 ≤ ｜Z ｜ ≤ 3 kpc. Our analysis shows that both the radial and vertical metallicity gradients are negative across much of the volume of the disk that is probed, and they exhibit significant spatial variations. Near the solar circle（7 ≤ RGC ≤ 11.5 kpc）, the radial gradient has a moderately steep, negative slope of-0.08 dex kpc-1near the midplane（｜Z ｜ 〈 0.1 kpc）, and the slope flattens with increasing ｜Z ｜. In the outer disk（11.5 〈 RGC ≤ 14 kpc）, the radial gradients have an essentially constant, much less steep slope of-0.01 dex kpc-1at all heights above the plane, suggesting that the outer disk may have experienced an evolutionary path different from that of the inner disk. The vertical gradients are found to flatten largely with increasing RGC. However, the vertical gradient of the lower disk（0 ≤ ｜Z ｜ ≤ 1 kpc）is found to flatten with RGC quicker than that of the upper disk（1 〈 ｜Z ｜ ≤ 3 kpc）.Our results should provide strong constraints on the theory of disk formation and evolution, as well as the underlying physical processes that shape the disk（e.g. gas flows,radial migration, and internal and external perturbations）.

The evolution of stellar metallicity gradients of the Milky Way disk from LSS-GAC main sequence turn-off stars: a two-phase disk formation history?

Accurate measurements of stellar metallicity gradients in the radial and vertical directions of the disk and their temporal variations provide important constraints on the formation and evolution of the Milky Way disk. We use 297 042 main sequence turn-off stars selected from the LAMOST Spectroscopic Survey of the Galactic Anticenter（LSS-GAC） to determine the radial and vertical gradients of stellar metallicity,△[Fe/H]/△R and △[Fe/H]/△｜Z ｜ of the Milky Way disk in the direction of the anticenter. We determine ages of those turn-off stars by isochrone fitting and measure the temporal variations of metallicity gradients. We have carried out a detailed analysis of the selection effects resulting from the selection, observation and data reduction of LSS-GAC targets and the potential biases of a magnitude limited sample on the determinations of metallicity gradients. Our results show that the gradients, both in the radial and vertical directions, exhibit significant spatial and temporal variations. The radial gradients yielded by stars with the oldest ages（ 11 Gyr） are essentially zero at all heights from the disk midplane, while those given by younger stars are always negative. The vertical gradients deduced from stars with the oldest ages（ 11 Gyr）are negative and only show very weak variations with Galactocentric distance in the disk plane, R, while those yielded by younger stars show strong variations with R.After being essentially flat at the earliest epochs of disk formation, the radial gradients steepen as age decreases, reaching a maximum（steepest） at age 7–8 Gyr, and then they flatten again. Similar temporal trends are also found for the vertical gradients. We infer that the assembly of the Milky Way disk may have experienced at least two distinct phases. The earlier phase is probably related to a slow, pressure-supported collapse of gas, when the gas settles down to the disk mainly in the vertical direction. In the later phase, there are significant radial flows of gas in the disk, and the rate of gas inflow near the solar neighborhood reaches a maximum around a lookback time of 7–8 Gyr.The transition between the two phases occurs around a lookback time between 8 and11 Gyr. The two phases may be responsible for the formation of the Milky Way＇s thick and thin disks, respectively. Also, as a consequence, we recommend that stellar age is a natural, physical criterion to distinguish stars from the thin and thick disks. From an epoch earlier than 11 Gyr to one between 8 and 11 Gyr, there is an abrupt, significant change in magnitude of both the radial and vertical metallicity gradients, suggesting that stellar radial migration is unlikely to play an important role in the formation of the thick disk.

Motion Law of Graviton in Three-Dimensional Space and Its Influence on Star Distribution of Spiral Galaxy

According to some fundamental hypotheses compatible with microphysics theory in allusion to property of graviton shot by the spiral galaxy, we set up a motion trace equation of graviton in the three-dimensional space, concluding method for measuring the velocity of graviton. This theory reveals formation mechanism of symmetric rotating arm image of the spiral galaxy. The rotating arm image conforms to Archimedes spiral. Under the condition of using dynamic constraints, the image that astrolabe is in thin-disk structure is naturally obtained. And then, we also deduce the law that astrolabe thickness h is inversely proportional to the square root of the distance rxy between astrolabe and galaxy center, according with actual crossrange galaxy observation image excellently. This article, by utilizing several typical galaxy observation images with completely different appearances and shapes, verifies the motion trace law of graviton in three-dimensional space. And the theoretical simulation data meet observation image data very well. As per the discovery in the simulation of three-dimensional theoretical model, changes of parameters in theoretical model will exert a great influence on the shape of galaxy. This theory owns exclusively important meaning, not only to astrophysics, but also to reconstruction and development of relativity theory and the whole basic physics theory, as well as breaking through the current dilemma in studying graviton property.

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.

Galactic disk bulk motions as revealed by the LSS-GAC DR2

We report a detailed investigation of the bulk motions of the nearby Galactic stellar disk, based on three samples selected from the LSS-GAC DR2： a global sample containing 0.57 million FGK dwarfs out to ～2 kpc, a local subset of the global sample consisting of ～5400 stars within 150 pc, and an anti-center sample containing ～4400AFGK dwarfs and red clump stars within windows a few degrees wide centered on the Galactic Anti-center. The global sample is used to construct a three-dimensional map of bulk motions of the Galactic disk from the solar vicinity out to ～2 kpc with a spatial resolution of ～250 pc. Typical values of the radial and vertical components of bulk motion range from-15 km s-1to 15 km s-1; in contrast, the lag behind the circular motion dominates the azimuthal component by up to ～15 km s-1. The map reveals spatially coherent, kpc-scale stellar flows in the disk, with typical velocities of a few tens of km s-1. Bending- and breathing-mode perturbations are clearly visible,and vary smoothly across the disk plane. Our data also reveal higher-order perturbations, such as breaks and ripples, in the profiles of vertical motion versus height. From the local sample, we find that stars from different populations exhibit very different patterns of bulk motion. Finally, the anti-center sample reveals a number of peaks in stellar number density in the line-of-sight velocity versus distance distribution, with the nearer ones apparently related to the known moving groups. The ＂velocity bifurcation＂ reported by Liu et al. at Galactocentric radii 10–11 kpc is confirmed. However,just beyond this distance, our data also reveal a new triple-peaked structure.

Measurements of the equivalent thicknesses of three-dimensional spiral galactic disks

Spiral arms are fitted after the data from the latest spiral galactic images released by the Sloan Digital Sky Survey are processed. Equivalent thicknesses of 42 spiral galactic disks are derived, which increase the foundational data for further research about spiral galaxies.

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.

Disk-Corona Model in Active Galactic Nuclei: an Observational Test

We compiled a sample of 98 radio-quiet active galactic nuclei observed by ASCA, Chandra, XMM-Newton, INTEGRAL and Swift with the aim of testing the formation of hot corona and the magnetic shear stress operating in a disk-corona system. We found a strong correlation between the hard X-ray luminosity, bolometric luminosity LBol and Eddington luminosity LEdd, in the sense that the fraction f of hard X-ray to the bolometric luminosity is inversely proportional to the Eddington ratio. This correlation favors the shear stress tensor being of the form of trФ∝ Pgas, with which the disk-corona structure is stable.

Extracting Energy Magnetically from Plunging Region of Black-Hole Accretion Disk

An analytical expression for the jet power extracted from the plunging region between a black hole （BH） horizon and the inner edge of the disk （hereafter the PL power） is derived based on an improved equivalent circuit in BH magnetosphere with a mapping relation between the radial coordinate of the plunging region and that of the remote astrophysical load. It is shown that the PL power is of great importance in explaining jet power and dominates over the BZ and DL powers for a wide value range of the BH spin. In addition, we show that the PL power derived in our model can be fitted with the strong jet powers of several 3CR FR I radio galaxies, which cannot be explained by virtue of the BZ mechanism. Furthermore, the condition for negative energy of the accreting particles in the plunging region is discussed with the validity of the second law of BH thermodynamics.

Gaseous versus Stellar Velocity Dispersion in Emission-Line Galaxies

We compare the ionized gas velocity dispersion σgas with the stellar velocity dispersion σ＊ in star-forming galaxies, composite galaxies, Low Ionization Nuclear Emissionline Regions （LINERs） and Seyfert 2s, compiled from a cross-identification of Sloan Digital Sky Survey Fourth Data Release （SDSS DR4） and Point Source Catalogue Redshift Survey （PSCz）. We measure σgas from the FWHMs of emission lines （Hα, [NⅡ]λλ6548, 6583 and [SⅡ]λλ6716, 6731）. A significant correlation between the gas and stellar velocity dispersion exists, despite substantial scatter. The mean value of the gas to stellar velocity dispersion ratio is close to unity. This suggests that gas velocity dispersion can substitute for the stellar velocity dispersion as a tracer of the gravitational potential well for all the four types of galaxies, but the involved uncertainties are different from type to type. We also studied -↑σgas, as a function of the redshift and the axial ratio to test the effects of aperture and galaxy inclination, and found that both effects are weak. Finally we checked the trend of -↑σgas/σ＊ with the infrared luminosity and found no significant correlation.

The pc-scale radio structure of MIR-observed radio galaxies

We investigated the relationship between the accretion process and jet properties by utilizing very long baseline array （VLBA） and mid-infrared （MIR） data for a sample of 45 3CRR radio galaxies selected with a flux density at 178MHz 〉 16.4Jy, 5 GHz very large array （VLA） core flux density ≥7 mJy and MIR observations. The pc-scale radio structure at 5 GHz is presented by using our VLBA observations for 21 sources acquired in February, 2016, the analysis of archival data for 16 objects and directly obtaining measurements for eight radio galaxies available from literatures. The accretion mode is constrained from the Eddington ratio with a dividing value of 0.01, which is estimated from the MIR-based bolometric luminosity and the black hole masses. While most Fanaroff-Riley type II radio galaxies （FRIIs） have higher Eddington ratio than Fanaroff-Riley type I radio galaxies （FRIs）, we found that there is indeed no single correspondence between the FR morphology and accretion mode with eight FRIIs at low accretion rate and two FRIs at high accretion rate. There is a significant correlation between the VLBA core luminosity at 5 GHz and the Eddington ratio. Various morphologies are identi- fied in our sample, including core only, single-sided core-jet and two-sided core-jet structures. We found that the higher accretion rate may be more likely related with the core-jet structure, thus generating a more extended jet. These results imply that the higher accretion rates are likely able to produce more powerful jets. There is a strong correlation between the MIR luminosity at 15 ktm and VLBA 5 GHz core luminosity, in favor of the tight relation between the accretion disk and jets. In our sample, the core brightness temperature ranges from 109 to 101338 K with a median value of 10^11.09K, indicating that systematically the beaming effect may not be significant. The exceptional cases, FRIs at high accretion rates and FRIIs at low accretion rates, are exclusively at the high and low ends, respectively, of the distribution of the flux ratio for VLBA core to 178 MHz flux density. It is not impossible that the locations of these sources are due to the recent shining or weakening of their central engines （i.e., both accretion and 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.

The photometric monitoring of γ-ray-loud narrow-line Seyfert 1 galaxy 1H0323+342 from 2006 to 2010

1H 0323＋342 is a γ-ray-loud narrow-line Seyfert 1 galaxy（NLS1）. The variability mechanism of γ-ray-loud NLS1 s remains unclear. We have observed 1H 0323＋342 photometrically from 2006 to2010 with a total of 41 nights of observations in order to constrain the variability mechanism. Intraday variabilities（IDVs） are detected on four nights. When considering the nights with time spans 〉 2 hours,the duty cycle is 28.3%. The average variability amplitude is 10.8% for IDVs and possibly variable nights. In the color-magnitude diagram, there are bluer-when-brighter chromatic trends for intraday and long-term timescales, which could be explained by the shock-in-jet model, and also could possibly be due to two distinct components or an accretion disk model.

New estimates of scale heights and spiral structures for non-edge-on spiral galaxies

On the basis of Poisson＇s equation for the logarithmic perturbation of matter density, we provide improved estimates of scale heights and spiral structures for non-edge-on spiral galaxies by subtracting the surface brightness distributions from observed images. As examples, the non-edge-on spiral galaxies PGC 24996, which is face-on, and M31, which is inclined, are studied. The scale height, pitch angle and inclination angle of M31, our nearest neighbor, that are presented in this work, agree well with previous research.