Astrophysics最新文献

{"title":"Environmental Dependence of Different Colors of Active Galactic Nucleus (AGN) Host Galaxies","authors":"Xin-Fa Deng,&nbsp;Zhi-Yong Wu","doi":"10.1007/s10511-023-09790-2","DOIUrl":"10.1007/s10511-023-09790-2","url":null,"abstract":"<div><div><p>Using the apparent-magnitude limited active galactic nucleus (AGN) host galaxy sample of the Sloan Digital Sky Survey Data Release 12 (SDSS DR12), we investigate the environmental dependence of the u-r, u-g, g-r, r-i and i-z colors of AGN host galaxies. We divide the whole apparent-magnitude limited AGN sample into many subsamples with a redshift binning size of ?z = 0.01, and analyze the environmental dependence of all five galaxy colors of subsamples in each redshift bin. It turns out that overall, all five galaxy colors of AGN host galaxies are weakly correlated with the local environment.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"173 - 180"},"PeriodicalIF":0.5,"publicationDate":"2023-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4113374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction to: Accelerating Kaluza-Klein Universe in Modified Theory of Gravitation","authors":"S. D. Katore,&nbsp;S. P. Hatkar,&nbsp;D. P. Tadas","doi":"10.1007/s10511-023-09789-9","DOIUrl":"10.1007/s10511-023-09789-9","url":null,"abstract":"","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"290 - 290"},"PeriodicalIF":0.5,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4008285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the Unified Scheme of γ-Ray Emitting Jetted Active Galactic Nuclei","authors":"A. I. Audu,&nbsp;F. C. Odo,&nbsp;E. U. Iyida,&nbsp;O. Okike,&nbsp;A. A. Ubachukwu","doi":"10.1007/s10511-023-09779-x","DOIUrl":"10.1007/s10511-023-09779-x","url":null,"abstract":"<div><div><p>The discovery of γ - ray emitting Seyfert galaxies has opened a new unified scheme of active galactic nuclei (AGN) in which jetted Seyfert galaxies are viewed as young counterparts of radio loud AGN. In this paper, we investigate the relationship between gamma-ray (γ - ray) properties of jetted Seyfert galaxies and those of traditionally radio galaxies, radio quasars and BL Lac objects. Results show that jetted Seyfert galaxies appear as low luminosity tail of the radio loud AGNs on the luminosity redshift (L_γ – z) plane, indicating an evolutionary link between them. Nevertheless, narrow-line Seyfert galaxies (NLS1s) do not share similar characteristics with Seyfert galaxies as they possess higher luminosities and redshift than Seyfert galaxies, suggestive that NLS1s are more evolved sources. Analyses of γ – ray and radio core-dominance show that for each subclass of jetted AGN, the beaming angle is wider for radio than for γ - ray emissions. While Seyferts and radio galaxies, on average, have similar low inclination to the line of sight, NLS1 objects have orientations similar to quasars and BL Lacs. There is a significant correlation (r ~ 0.7) between the γ - ray core dominance and γ - ray luminosity. The results are consistent with the revised unification scheme and suggests that NLS1s are highly beamed sources whose parent populations can be found among the regular Seyferts and/or radio galaxies</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"159 - 172"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5179642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the Centenary of L. V. Mirzoyan","authors":"","doi":"10.1007/s10511-023-09778-y","DOIUrl":"10.1007/s10511-023-09778-y","url":null,"abstract":"","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"157 - 158"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5177299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-Scale Electric Currents in Coronal Heating Processes above Active Regions on the Sun","authors":"Yu.A. Fursyak","doi":"10.1007/s10511-023-09786-y","DOIUrl":"10.1007/s10511-023-09786-y","url":null,"abstract":"<div><div><p>This paper poses the problem of studying the role of large-scale electric currents propagating in the upper layers of the solar atmosphere in processes of coronal heating of the sun. For detecting and calculating the magnitude of the large-scale electric current, data on the distribution of the components of the magnetic field vector in the photosphere provided by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used. Photoheliograms of the sun’s corona in the ultraviolet radiation channels at 131, 171, 193, and 211 Å provided by the Atmospheric Imaging Assembly (AIA/SDO) were used to estimate the temperature in the corona above active regions (ARs). The dynamics of the large-scale current and the average temperature in 9 regions with different levels of flare activity of the corona above the ARs have been studied and charts of the spatial distribution of the temperature in the corona above the ARs have been constructed. The following results have been obtained: 1. Heating of the coronal matter owing to ohmic dissipation of large-scale electric currents proceeds in a stationary regime. 2. The increase in the average temperature in the corona above an AR during solar flares to <span>(&lt;overline{mathrm{log}T }&gt;=6.3-6.5)</span> (2.0-3.2 MK) is caused, not only by heating of coronal structures by large-scale electric currents, but also by other processes at coronal elevations. 3. For the NOAA 11899 and 12494 regions a reduction in the average temperature of the corona to <span>(&lt;overline{mathrm{log}T }&gt;=5.7)</span> (0.5-0.6 MK) was observed with a simultaneous drop in the values of the large-scale electric current to zero. These observations indicate that the mechanism for heating of the corona by ohmic dissipation of electric currents is shut off at zero values (within the computational errors) of the large-scale electric current. 4. In the NOAA regions 12192 and 12371, when constructing charts of the temperature distribution in the corona outside flare events, hot structures with temperatures ≥ 10 MK were observed outside the flare events which appear to mark the location of the channel of a large-scale electric current at coronal elevations. For the NOAA region 12192 this assumption is confirmed by a numerical simulation carried out in 2016.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"242 - 257"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5178554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiwavelength Properties of Selected High Redshift Blazars","authors":"G. Harutyunyan","doi":"10.1007/s10511-023-09780-4","DOIUrl":"10.1007/s10511-023-09780-4","url":null,"abstract":"<div><div><p>High-redshift blazars detected in the γ -ray band are the most powerful steady objects in the universe. Multiwavelength observations of these distant objects are of particular interest as they can help to understand the γ -ray evolution of blazars as well as the formation and propagation of relativistic jets in the early epochs of the Universe. In this study, we investigate the origin of broadband emission from 7 blazars with redshifts greater than 2.5 by analyzing the data accumulated with Swift UVOT/XRT and Fermi-LAT. We observe several flaring periods with significant increases in flux and hardening of the photon index in the high-energy γ -ray band for PKS 1830-211 (z = 2.507), LQAC 247-061 (z = 2.578), TXS 0536+145 (z = 2.690), and 4C+41.32 (z = 2.550). PKS 1830-211 was in an extraordinarily bright state on MJD 58596.49 when the 3-day averaged flux increased up to (1.74 ± 0.04)·10^–5 photon cm^-2 s^-1. The X-ray emission of PKS 1830-211 is also strongly variable and is characterized by a hard photon index in the range of 0.34-0.94. To model the time-averaged broadband spectral energy distribution of the considered sources, we used a one-zone leptonic emission mechanism for the inverse Compton scattering, considering both synchrotron and external photons. We estimated the corresponding parameters of the emitting particles as well as the energetics of the jet.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"181 - 193"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5179649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"TYC 1417-891-1 and TYC 1478-742-1: Eclipsing Variable Stars. The Gaia EDR3 and TESS Photometric Data","authors":"K. K. Gigoyan,&nbsp;K. S. Gigoyan,&nbsp;A. Sarkissian,&nbsp;M. Meftah,&nbsp;G. R. Kostandyan,&nbsp;F. Rahmatullaeva","doi":"10.1007/s10511-023-09781-3","DOIUrl":"10.1007/s10511-023-09781-3","url":null,"abstract":"<div><div><p>Based on the TESS (Transiting Exoplanet Survey Satellite) phase dependent light curves, we confirm the eclipsing type variability nature for two G-type dwarfs: TYC 1417-891-1 and TYC 1478-742-1. Both objects show EA (Algol-type) light curves morphology. Orbital period for TYC 1417-891-1 is P ≈ 8.0 day and for TYC 1478-742-1, P ≈ 13.6 day. We present Gaia EDR3 and TESS catalogue important physical parameters as well as LAMOST spectra. Both objects are relatively bright and are located at a distance of 260.59 (±3.21) pc (TYC 1417-891-1) and 117.42 (±0.74) pc (TYC 1478-742-1). The TESS light curve of TYC 1478-742-1 shows also flares as well. We discuss possible nature of the secondary and faint objects around these stars.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"194 - 204"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5179650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photometric Activity of CQ Tau over a Time Interval of 125 Years","authors":"V. P. Grinin,&nbsp;L. V. Tambovtseva,&nbsp;O. Yu. Barsunova,&nbsp;D. N. Shakhovskoy","doi":"10.1007/s10511-023-09785-z","DOIUrl":"10.1007/s10511-023-09785-z","url":null,"abstract":"<div><div><p>The star CQ Tau belongs to the family of UX Ori type stars and is characterized by very complicated photometric behavior and a complex structure of its circumstellar environment. Based on published photometric data, in this article we construct a light curve for this star covering 125 years. It implies that besides a random component characteristic of UX Ori type stars, the changes in brightness also include a large amplitude periodic component with a period of 10 years. It existence was suspected previously and new observations confirm its reality. This indicates the existence of a second component in the neighborhood of the star. Matter flows and density waves caused by the motion of the companion lead to periodic changes in the circumstellar extinction and brightness of the star. This result is discussed in the context of recent observations of CQ Tau with high angular resolution.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"235 - 241"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5178879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theory of Classical Gaseous Polytropes in an Integral Representation. II. Analytic Approximations to the Emden Functions and Density Profiles in a Closed Form","authors":"G. A. Saiyan","doi":"10.1007/s10511-023-09788-w","DOIUrl":"10.1007/s10511-023-09788-w","url":null,"abstract":"<div><div><p>Analytic approximations are presented for the exact solutions of the Volterra type nonlinear integral equation of the second kind for classical gaseous polytropes in closed form. This equation is considered as the integral equivalent of the Lane-Emden differential equation with boundary conditions which describes the standard polytropic models in terms of a Cauchy problem. With the aid of a linear approximation of this equation and general heuristic considerations of a physical character, as well as with the aid of a graphical model and variation of the parameters of the approximating functions, approximate expressions for the Emden functions and the dimensionless density are obtained in closed form with a mean square accuracy from ~10^-4 to a few percent for a series of values of the polytropic index n of practical interest (n = 0.5, 3, 4, 6, ∞). Our previous approximation for the spatial density of the isothermal model is compared with a pseudo-isothermal law describing the distribution of the density of dark matter surrounding spiral galaxies and used by various authors for studying their rotation curves.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"273 - 289"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5179607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of Spectrum Lines in an Inhomogeneous Atmosphere Illuminated by Nonstationary Energy Sources","authors":"A. G. Nikoghossian","doi":"10.1007/s10511-023-09787-x","DOIUrl":"10.1007/s10511-023-09787-x","url":null,"abstract":"<div><div><p>The effect of the inhomogeneity of a scattering and absorbing medium of finite thickness on the evolution of spectrum lines which appear when it is illuminated by nonstationary energy sources is examined. Special attention is devoted to the role of scattering in the continuum spectrum. It is assumed that the inhomogeneity arises from the variation in the scattering coefficient with depth, which may be increasing or decreasing on approaching the illuminated boundary. Two types of nonstationarity of the external energy source are studied with a shape corresponding to δ(t), the Dirac function, and H(t), the unit step function of Heaviside. The question of using observed time changes in the profiles of spectrum lines for determining their optical characteristics, the frequency dependence of the external energy sources, and the physical properties of the illuminated medium itself, is studied.</p></div></div>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"66 2","pages":"258 - 272"},"PeriodicalIF":0.5,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5184297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}