W1 W2 Research Articles

Investigation of groundwater induced land subsidence in Ludhiana City using InSAR and Sentinel-1 data

Land Subsidence (LS) is a vertically downward motion of land surface due to various reasons such as natural processes and anthropogenic activities especially excessive exploitation of groundwater. LS has adverse effects on substantial infrastructural damage, severe environmental problems, extensive economic losses, and significant societal impacts. In this study, we investigated the LS of Ludhiana city, a densely populated, largest and major industrial city of Punjab state, India. We presented a comprehensive methodology of Short BAseline Subset Interferometric Synthetic Aperture Radar (SBASInSAR) for LS measurement using an open-source computational environment. We generated 197 interferograms from 65 Sentinel-1A images acquired in descending pass between September 2019–July 2022 for deriving radar line of sight (LOS) displacement time-series and mean LOS velocity. Deformation results showed that the southern, and south-eastern parts of the city had been consistently moving downward with a mean subsidence rate of 24.7 mm/yr, while in western, few small patches in eastern and northern regions it ranges from 2 to 21 mm/yr, 3–20 mm/yr and 4–16 mm/yr respectively. The standard deviation of mean LOS velocity was observed between 0.7 and 3.3 mm/yr with majority values < 2 mm/yr. SBASInSAR results were compared with six Groundwater Level (GWL) wells observations, and both measurements generally agreed well at GWL locations (W1–W6) except W1–W2. For assessing the influence of groundwater change on LS, a correlation analysis was performed, and correlation of 0.50, 0.47, 0.81, 0.77, 0.84, and 0.64 was observed at GWL stations (W1–W6) respectively. Overall comparison of InSAR and GWL measurements are found in good agreement and significantly correlated, which can provide sufficiently detailed information about LS.

Gaia17bpp: A Giant Star with the Deepest and Longest Known Dimming Event

We report the serendipitous discovery of Gaia17bpp/2MASS J19372316+1759029, a binary star with a deep single large-amplitude dimming event of ∼4.5 mag that lasted over 6.5 yr. Using the optical-to-IR spectral energy distribution (SED), we constrain the primary star to be a cool giant M0III star with effective temperature T eff = 3850 K and radius R = 58 R ⊙. Based on the SED fitting, we obtained a bimodal posterior distribution of primary stellar masses with a stronger preference for a 1.5 M ⊙ mass star. Within the last 66 yr of photometric coverage, no other significant dimming events of this depth and duration were identified in the optical light curves. Using a Gaussian process, we fit a generalized Gaussian distribution to the optical and IR light curves and conclude that the dimming event exhibits moderate asymmetries from optical to IR. At the minimum of the dimming event, the Wide-field Infrared Survey Explorer color (W1–W2) differed by ∼0.2 mag relative to the primary star color outside the dimming event. The ingress and egress colors show a shallow reddening profile. We suggest that the main culprit of the dimming event is likely due to the presence of a large, optically thick disk transiting the primary giant star. By fitting a monochromatic transit model of an oblate disk transiting a star, we found good agreement with a slow-moving (0.005 km s−1) disk with a ∼1.4 au radius. We propose that Gaia17bpp belongs to a rare binary star population similar to the ϵ Aurigae system, which consists of a secondary star enshrouded by an optically thick debris disk.

The Chandra Source Catalog Normal Galaxy Sample

We present the extensive and well-characterized Chandra X-ray Galaxy Catalog (CGC) of 8547 galaxy candidates in the redshift range z ∼ 0.04–0.7, optical luminosity 1010–1011 Lr ⊙, and X-ray luminosity (0.5–7 keV) L X = 2 × 1040–2 × 1043 erg s−1. We estimate a ∼5% false-match fraction and contamination by quasi-stellar objects (QSOs). The CGC was extracted from the Chandra Source Catalog version 2 (CSC2) by cross-correlating with optical and IR all-sky survey data, including the Sloan Digital Sky Survey, Pan-STARRS, DESI Legacy, and Wide-field Infrared Survey Explorer (WISE). Our selection makes use of two main criteria that we have tested on the subsample with optical spectroscopical identification. (1) A joint selection based on X-ray luminosity (L X) and X-ray-to-optical flux ratio (F XO), which recovers 63% of the spectroscopically classified galaxies with a small contamination fraction (7%), which is a significant improvement over methods using L X or F XO alone (<50% recovery). (2) A joint W1–W2 (W12) WISE color and L X selection that proves effective in excluding QSOs and improves our selection by recovering 72% of the spectroscopically classified galaxies and reducing the contamination fraction (4%). Of the CGC, 24% was selected by means of optical spectroscopy; 30% on the basis of L X, F XO, and W12; and 46% by using either the L X–F XO or the L X–W12 selection criteria. We have individually examined the data for galaxies with z < 0.1, which may include more than one CSC2 X-ray source, leading to the exclusion of 110 local galaxies. Our catalog also includes near-IR and UV data and galaxy morphological types.

Sum of the Fourier coefficients of SL(3,Z) Hecke Maass forms over quadratics

Let A(1,n) denote the (1,n)-th Fourier coefficients of a SL(3,Z) Hecke eigenform. Let Q(x,y) be a symmetric positive definite quadratic form. In this paper, we shall prove thatS:=∑m≤X∑n≤XA(1,Q(m,n))W1(mX)W2(nX)≪X2−168+ϵ, for any positive ϵ>0, where W1 and W2 are smooth bump functions supported on the interval [1,2].

Improving the selection of changing-look AGNs through multiwavelength photometric variability

ABSTRACT We present second epoch optical spectra for 30 changing-look (CL) candidates found by searching for Type-1 optical variability in a sample of active galactic nuclei (AGNs) spectroscopically classified as Type 2. We use a random-forest-based light-curve classifier and spectroscopic follow-up, confirming 50 per cent of candidates as turning-on CLs. In order to improve this selection method and to better understand the nature of the not-confirmed CL candidates, we perform a multiwavelength variability analysis including optical, mid-infrared (MIR), and X-ray data, and compare the results from the confirmed and not-confirmed CLs identified in this work. We find that most of the not-confirmed CLs are consistent with weak Type 1s dominated by host-galaxy contributions, showing weaker optical and MIR variability. On the contrary, the confirmed CLs present stronger optical fluctuations and experience a long (from five to ten years) increase in their MIR fluxes and the colour W1–W2 over time. In the 0.2–2.3 keV band, at least four out of 11 CLs with available SRG/eROSITA detections have increased their flux in comparison with archival upper limits. These common features allow us to select the most promising CLs from our list of candidates, leading to nine sources with similar multiwavelength photometric properties to our CL sample. The use of machine learning algorithms with optical and MIR light curves will be very useful to identify CLs in future large-scale surveys.

A New Wide-field Infrared Survey Explorer Calibration of Stellar Mass

We derive new empirical scaling relations between Wide-field Infrared Survey Explorer (WISE) mid-IR (MIR) galaxy photometry and well-determined stellar masses from spectral energy distribution modeling of a suite of optical–infrared photometry provided by the Data Release 4 (DR4) Catalog of the GAMA-KiDS-VIKING survey of the southern G23 field. The MIR source extraction and characterization are drawn from the WISE Extended Source Catalogue and the archival ALLWISE catalog, combining both resolved and compact galaxies in the G23 sample to a redshift of 0.15. Three scaling relations are derived: W1 3.4 μm luminosity versus stellar mass, and WISE W1–W2, W1–W3 colors versus mass-to-light ratio (M/L, sensitive to a variety of galaxy types from passive to star-forming). For each galaxy in the sample, we then derive the combined stellar mass from these scaling relations, producing M ⋆ estimates with better than ∼25%–30% accuracy for galaxies with >109 M ⊙ and <40%–50% for lower-luminosity dwarf galaxies. We also provide simple prescriptions for rest-frame corrections and estimating stellar masses using only the W1 flux and the W1–W2 color, making stellar masses more accessible to users of the WISE data. Given a redshift or distance, these new scaling relations will enable stellar mass estimates for any galaxy in the sky detected by WISE with high fidelity across a range of M/L ratios.

NEOWISE Variability of the New Gaia Herbig Ae/Be and Classical Be Stars—Variability Sample and Statistical Analysis

Light variability is an essential attribute of young stellar objects (YSOs) at the pre-main-sequence (PMS) stage, which can be treated as an indicator to trace star formation. We present a statistical study on the infrared NEOWISE variability of new and large-sized PMS stars as well as Herbig Ae/Be (HAeBe) and classical Be (CBe) stars identified from Gaia Data Release 2. A total of 3792 (including 714 HAeBe), 417, and 473 NEOWISE variable sources were detected from the catalog of 8470 PMS (including 1361 HAeBe), 693 CBe, and 1309 uncertain (possibly belonging to either HAeBe or CBe) stars, respectively. We found that 80% of the PMS variables are dominated by irregular infrared variability, whereas variables in the CBe and uncertain categories exhibit comparable contributions from secular (linear, curved, and periodic) and stochastic (burst, drop, and irregular) variables. This, in combination with infrared W1–W2 colors, W4 luminosities, and the spectral energy distribution slope at near- and mid-infrared wavelengths, suggests different evolutionary stages of the PMS (including HAeBe), uncertain, and CBe stars, from less to more evolved. A statistical analysis of variable source properties (e.g., period and fractional amplitude) further reveals a potential sequence possibly associated with disk evolution for different types of light curves (from linear, to curved, periodic, stochastic, and nonvariable stars). Possible mechanisms for the variable sources are suggested to be related to either extinction via circumstellar matter, or contribution of multiple systems surrounding the YSOs, as opposed to variable accretion (e.g., episodic accretion or accretion burst).

Determination of the Dominating Coalescence Pathways in Double Emulsion Formulations by Use of Microfluidic Emulsions

In water-in-oil-in-water (W1/O/W2) double emulsions several irreversible instability phenomena lead to changes. Besides diffusive processes, coalescence of droplets is the main cause of structural changes. In double emulsions, inner droplets can coalesce with each other (W1–W1 coalescence), inner droplets can be released via coalescence (W1–W2 coalescence) and oil droplets can coalesce with each other (O–O coalescence). Which of the coalescence pathways contributes most to the failure of the double emulsion structure cannot be determined by common measurement techniques. With monodisperse double emulsions produced with microfluidic techniques, each coalescence path can be observed and quantified simultaneously. By comparing the occurrence of all possible coalescence events, different hydrophilic surfactants in combination with PGPR are evaluated and discussed with regard to their applicability in double emulsion formulations. When variating the hydrophilic surfactant, the stability against all three coalescence mechanisms changes. This shows that measuring only one of the coalescence mechanisms is not sufficient to describe the stability of a double emulsion. While some surfactants are able to stabilize against all three possible coalescence mechanisms, some display mainly one of the coalescence mechanisms or in some cases all three mechanisms are observed simultaneously.

Oil Droplet Coalescence in W/O/W Double Emulsions Examined in Models from Micrometer- to Millimeter-Sized Droplets

Water-in-oil-in-water (W1/O/W2) double emulsions must resist W1–W1, O–O and W1–W2 coalescence to be suitable for applications. This work isolates the stability of the oil droplets in a double emulsion, focusing on the impact of the concentration of the hydrophilic surfactant. The stability against coalescence was measured on droplets ranging in size from millimeters to micrometers, evaluating three different measurement methods. The time between the contact and coalescence of millimeter-sized droplets at a planar interface was compared to the number of coalescence events in a microfluidic emulsion and to the change in the droplet size distributions of micrometer-sized single and double emulsions. For the examined formulations, the same stability trends were found in all three droplet sizes. When the concentration of the hydrophilic surfactant is reduced drastically, lipophilic surfactants can help to increase the oil droplets’ stability against coalescence. This article also provides recommendations as to which purpose each of the model experiments is suited and discusses advantages and limitations compared to previous research carried out directly on double emulsions.

A Catalog of Host Galaxies for WISE-selected AGN: Connecting Host Properties with Nuclear Activity and Identifying Contaminants

Abstract We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts z ∼ 3 and will be useful for studies focused on AGN or their host galaxy physical properties. We first show that the most likely non-AGN contaminants are galaxies at redshifts z = 0.2–0.3, with relatively blue W1–W2 colors, and with high specific SFRs for which the dust continuum emission is elevated in the W2 filter. Toward increasingly lower redshifts, WISE AGN host galaxies have systematically lower specific SFRs relative to those of normal star-forming galaxies, likely due to decreased cold gas fractions and the time delay between global star formation and AGN triggering. Finally, WISE AGN obscuration is not strongly correlated with AGN bolometric luminosity but shows a significant negative correlation with the Eddington ratio. This result is consistent with a version of the receding torus model in which the obscuring material is located within the supermassive black hole gravitational sphere of influence and the dust inner radius increases due to radiation pressure.

Efficacy evaluation of case-specific approach for surgical treatment of incisional ventral hernia

&lt;b&gt;Aim:&lt;/b&gt; The aim of this research is to improve the results of surgical treatment of incisional ventral hernia by applying a case-specific approach and a new method of plastic repair of the anterior abdominal wall.&lt;br/&gt; &lt;br/&gt; &lt;b&gt;Methods:&lt;b/&gt; The prospective controlled dynamic study is based on incisional ventral hernia treatment results with the use of meshed endoprostheses among 219 patients. On-lay alloplasty was used in patients younger than 60 years of age, without severe concomitant pathology, with small and medium hernias and anterior abdominal wall defect of up to 10 cm (W1–W2).&lt;br/&gt; &lt;br/&gt; &lt;b&gt;Results:&lt;b/&gt; The article shows a selection algorithm for anterior abdominal wall plastic repair method. It goes through advantages of the author’s proprietary technique. The article displays frequency and patterns of complications, with life quality of the patients after various prosthetic plastic repairs. In the main group, positive treatment results were observed in 65.0%, longterm results of the operation were observed in 88.4%, complications occurred in 13.6%, relapse in 4.5%. «Onlay» treatment tactics showed positive results in 59.4%, long-term results of the operation were observed in 74.7%, complications occurred in 40%, relapse in 3.1%. After «sublay» intervention, excellent results were observed in 40.0% of patients, long-term results of the operation were observed in 81.9%, complications occurred in 12%, and relapse in 1.4%&lt;br/&gt; &lt;br/&gt;

Influence of Hydrophilic Surfactants on the W1–W2 Coalescence in Double Emulsion Systems Investigated by Single Droplet Experiments

Double emulsions are a promising formulation for encapsulation and targeted release in pharmaceutics, cosmetics and food. An inner water phase is dispersed in an oil phase, which is again emulsified in a second water phase. The encapsulated inner water phase can be released via diffusion or via coalescence, neither of which is desired during storage but might be intended during application. The two interfaces in a double emulsion are stabilized by a hydrophilic and a lipophilic surfactant, to prevent the coalescence of the outer and the inner emulsion, respectively. This study focuses on the influence of the hydrophilic surfactant on the release of inner water or actives encapsulated therein via coalescence of the inner water droplet with the outer O–W2 interface. Since coalescence and diffusion are difficult to distinguish in double emulsions, single-droplet experiments were used to quantify differences in the stability of inner droplets. Different lipophilic (PGPH and PEG-30 dipolyhydroxylstearate) and hydrophilic surfactants (ethoxylates, SDS and polymeric) were used and resulted in huge differences in stability. A drastic decrease in stability was found for some combinations, while other combinations resulted in inner droplets that could withstand coalescence longer. The destabilization effect of some hydrophilic surfactants depended on their concentration, but was still present at very low concentrations. A huge spread of the coalescence time for multiple determinations was observed for all formulations and the necessary statistical analysis is discussed in this work. The measured stabilities of single droplets are in good accordance with the stability of double emulsions for similar surfactant combinations found in literature. Therefore, single droplet experiments are suggested for a fast evaluation of potentially suitable surfactant combinations for future studies on double-emulsion stability.

Subarcsecond Mid-infrared View of Local Active Galactic Nuclei. IV. The L- and M-band Imaging Atlas*

Abstract We present the largest currently existing subarcsecond 3–5 μm atlas of 119 local (z &lt; 0.3) active galactic nuclei (AGNs). This atlas includes AGNs of five subtypes: 22 are Seyfert 1; five are intermediate Seyferts; 46 are Seyfert 2; 26 are low-ionization nuclear emission regions; and 20 are composites/starbursts. Each active galactic nucleus was observed with the Very Large Telescope Infrared Spectrometer and Array Camera (ISAAC) in the L and/or M bands between 2000 and 2013. We detected at 3σ confidence 92 sources in the L band and 83 sources in the M band. We separated the flux into unresolved nuclear flux and resolved the flux through two-Gaussian fitting. We report the nuclear flux, extended flux, apparent size, and position angle of each source, giving 3σ upper limits for sources that are undetected. Using Wide-field Infrared Survey Explorer (WISE) W1- and W2-band photometry we derived relations predicting the nuclear L and M fluxes for Sy1 and Sy2 AGNs based on their W1–W2 color and WISE fluxes. Lastly, we compare the measured mid-infrared colors to those predicted by dusty torus models SKIRTOR, CLUMPY, CAT3D, and CAT3D-WIND, finding the best agreement with the latter. We find that models including polar winds best reproduce the 3–5 μm colors, indicating that it is an important component of dusty torus models. We found that several AGNs are bluer than models predict. We discuss several explanations for this and find that it is most plausibly stellar light contamination within the ISAAC L-band nuclear fluxes.

A detailed study of X-ray cavities in the intracluster environment of the cool core cluster Abell 3017

ABSTRACT We present a detailed analysis of a cool-core galaxy cluster Abell 3017, at a redshift of z = 0.219, which has been identified to be merging with its companion cluster Abell 3016. This study has made use of X-ray (Chandra), ultraviolet (UV) [Galaxy Evolution Explorer(GALEX)], optical [European Southern Observatory (ESO)/very large telescope (VLT)], mid-infrared [(Wide-field Infrared Survey Explorer (WISE)], and radio upgraded Giant Metrewave radio telescope (uGMRT) observations of this cluster. Using various image processing techniques, such as unsharp masking, 2D fits using β models, contour binning and the use of surface brightness profiles, we show the existence of a pair of X-ray cavities, at a projected distance of ∼20 arcsec (70 kpc) and ∼16 arcsec (57 kpc), respectively, from the core of Abell 3017. We also detect an excess of X-ray emission located at ∼25 arcsec (88 kpc) south of the centre of Abell 3017, is likely due to the bulk motions in the intracluster medium either by gas sloshing or ram-pressure striping due to a merger. We find that the radio lobes are responsible for the observed X-ray cavities detected in this system. The lower values of mid-infrared WISE colour [W1–W2] and [W2–W3] imply that the central BCG of Abell 3017 is a star-forming galaxy. The current star formation rate of the central BCG, estimated from the H α and GALEX far-ultraviolet (FUV) luminosities, are equal to be ∼5.06 ± 0.78 and ∼9.20 ± 0.81 $\rm M_{\odot }$ yr−1, respectively. We detect, for the first time, a radio phoenix ∼150 kpc away from the radio core, with a spectral index of (α ≤ −1.8). We also report the detection of $\rm ~Pa\,\alpha$ emission in this cluster using ESO VLT SINFONI imaging data.

A search for X-ray absorbed sources in the 3XMM catalogue using photometric redshifts and Bayesian spectral fits

Since its launch in 1999, the XMM-Newton mission has compiled the largest catalogue of serendipitous X-ray sources, with the 3XMM being the third version of this catalogue. This was possible thanks to the combination of a large effective area (5000 cm2 at 1 keV) and a wide field of view (30 arcmin). The 3XMM-DR6 catalogue contains about 470 000 unique X-ray sources over an area of 982 deg2. A significant fraction of these (100 178 sources) have reliable optical, near-(NIR), and mid-infrared (MIR) counterparts in the SDSS, PANSTARRS, VIDEO, UKIDSS, and WISE surveys. In a previous paper we presented photometric redshifts for these sources using the TPZ machine-learning algorithm. About a quarter of these (22 677) have adequate photon statistics, meaning that a reliable X-ray spectrum can be extracted. Owing to both the X-ray counts selection and the optical counterpart constraint, the sample above is biased towards the bright sources. Here, we present XMMFITCAT-Z: a spectral fit catalogue for these sources using the Bayesian X-ray Analysis technique. To demonstrate the potential of the present catalogue, we comment on the optical and MIR colours of the 765 X-ray absorbed sources with NH &gt; 1022 cm−2. We show that a considerable fraction of X-ray-selected AGNs would not be classified as AGNs following the MIR W1–W2 versus W2 selection criterion. These are AGNs with lower luminosities, where the contribution of the host galaxy to the MIR emission is non-negligible. Only one-third of obscured AGNs in X-rays present red colours or r–W2 &gt; 6. Also, it appears that the r–W2 criterion, often used in the literature for the selection of obscured AGNs, produces very different X-ray absorbed AGN samples compared to the standard X-ray selection criteria.

Interpretation of magma transport through saucer sills in shallow sedimentary strata using an automated machine learning approach

In sedimentary basins, emplacement of sheet intrusions such as sill complexes significantly contributes to the transport and storage of hot magma at shallow level. Such emplacement at shallow depth leads in doming of the overburden, which acts as plausible structural traps useful for hydrocarbon exploration. The petroliferous Canterbury Basin, SE offshore New Zealand, is a classic example of such phenomena, where saucer-shaped magmatic sills are emplaced within the Cretaceous to Eocene succession. This has resulted into forced folds and hydrothermal vents above the sill terminations within the Eocene sequences. The present study attempts to capture this scenario through a neural network by designing meta-attributes, called as the Sill Cube (SC) and Fluid Cube (FC). The meta-attributes are computed by unifying different seismic attributes that are trained over interpreter's knowledge on the geologic targets following a supervised scheme of neural learning. The approach prominently arrests the structural geometry of sill complexes and fluxed-out magmatic fluids within the Cretaceous to Eocene strata from 3D seismic reflection data of the Waka prospect, offshore Canterbury Basin. Based on the meta-attribute interpretation, the individual sills within the Waka prospect cover areas of ~1.5 km2 to 17 km2, where the principal sills namely the Sill W1 and Sill W2 spread over an area of ~12 km2 and 17 km2, respectively. Moreover, the fluxed out magmatic fluids vertically rise to a height of ~800 m through hydrothermal vents from the tip of the principal sills, and uplift the overburden. Such approach is automated and incorporates interpreter's acquaintances to effectively capture subsurface magmatic activities for better interpretation of 3D seismic data.

Dust reverberation mapping of type 2 AGN NGC 2110 realized with X-ray and 3–5 μm IR monitoring

ABSTRACT The dust reverberation mapping is one of powerful methods to investigate the structure of the dusty tori in active galactic nuclei (AGNs), and it has been performed on more than a hundred type 1 AGNs. However, no clear results have been reported on type 2 AGNs because their strong optical/UV extinction completely hides their accretion disc emission. Here, we focus on an X-ray-bright type 2 AGN, NGC 2110, and utilize 2–20 keV X-ray variation monitored by MAXI to trace disc emission, instead of optical/UV variation. Comparing it with light curves in the WISE infrared (IR) W1 band ($\lambda =3.4~\mu$m) and W2 band ($\lambda =4.6~\mu$m) with cross-correlation analyses, we found candidates of the dust reverberation time lag at ∼60, ∼130, and ∼1250 d between the X-ray flux variation and those of the IR bands. By examining the best-fitting X-ray and IR light curves with the derived time lags, we found that the time lag of ∼130 d is most favoured. With this time lag, the relation between the time lag and luminosity of NGC 2110 is consistent with those in type 1 AGNs, suggesting that the dust reverberation in NGC 2110 mainly originates in hot dust in the torus innermost region, the same as in type 1 AGNs. As demonstrated by the present study, X-ray and IR simultaneous monitoring can be a promising tool to perform the dust reverberation mapping on type 2 AGNs.

Correlates of tobacco product initiation among youth and adults in the USA: findings from the PATH Study Waves 1–3 (2013–2016)

ObjectiveTo report on demographic and tobacco product use correlates of tobacco product initiation (cigarettes, electronic nicotine delivery systems (ENDS), cigars, hookah and smokeless tobacco) among the US population.DesignData were from...

The mid-infrared variability of the SDSS optical quasars

Based on the Seventh Data Release (DR7) quasar catalog from the Sloan Digital Sky Survey, we investigate the variability of optical quasars in W1, W2, W3 and W4 bands of the Wide-field Infrared Survey Explorer (WISE) and the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE). Adopting the structure function (SF) method, we calculate the SF (δ t = 1 yr) which shows no obvious correlations with the bolometric luminosity, the black hole mass and the Eddington ratio. The ensemble SFs in W1 and W2 bands show that the SF slopes are steeper than those in previous studies which may be caused by different cadence and observational epoch number. We further investigate the relation of variability amplitude σm between mid-infrared band and optical band, but no obvious correlation is found. No correlation is found between W1–W2 and g – r color. We think that the mid-infrared emission of quasars may be smoothed out by the extended dust distribution, thus leading to no obvious correlation. For the radio-loud quasar sub-sample, we further analyze the relation between the variability amplitude in the mid-infrared band and the radio luminosity at 6 cm, but no obvious correlations are found, which indicate the mid-infrared emission contributed from the synchrotron radiation of the relativistic jet is very weak.

О 6-мерных AH-подмногообразиях класса W1⊕W2⊕W4 алгебры Кэли

Six-dimensional submanifolds of Cayley algebra equipped with an almost Hermitian structure of class W1 W2 W4 defined by means of three-fold vector cross products are considered. As it is known, the class W1 W2 W4 contains all Kählerian, nearly Kählerian, almost Kählerian, locally conformal Kählerian, quasi-Kählerian and Vaisman — Gray manifolds. The Cartan structural equations of the W1 W2 W4 -structure on such six-dimensional submanifolds of the octave algebra are obtained. A criterion in terms of the configuration tensor for an arbitrary almost Hermitian structure on a six-dimensional submanifold of Cayley algebra to belong to the W1 W2 W4 -class is established. It is proved that if a six-dimensional W1 W2 W4 -submanifold of Cayley algebra satisfies the quasi-Sasakian hypersurfaces axiom (i.e. a hypersurface with a quasi-Sasakian structure passes through every point of such submanifold), then it is an almost Kählerian manifold. It is also proved that a six-dimensional W1 W2 W4 -submanifold of Cayley algebra satisfies the eta-quasi-umbilical quasi-Sasakian hypersurfaces axiom, then it is a Kählerian manifold.