Astrophysics最新文献

{"title":"BSN: First Photometric Light Curve Analysis of Two W-Type Contact Binary Systems OP Boo and V0511 Cam","authors":"A. Poro,&nbsp;M. Tanriver,&nbsp;A. Keskin,&nbsp;A. Bulut,&nbsp;S. Rabieefar,&nbsp;M. M. Gharghabi,&nbsp;F. Walter,&nbsp;S. Holy","doi":"10.1007/s10511-024-09834-1","DOIUrl":"10.1007/s10511-024-09834-1","url":null,"abstract":"<p>This study presented the first light curve analysis of the OP Boo and V0511 Cam binary stars, which was conducted in the frame of the Binary Systems of South and North (BSN) Project. Photometric ground-based observations were conducted with standard filters at two observatories in the Czech Republic. We computed a new ephemeris for each of the systems using our extracted times of minima, TESS data, and additional literature. Linear fits for O-C diagrams of both systems were considered using the Markov Chain Monte Carlo (MCMC) method. The light curves were analyzed using the Wilson-Devinney (WD) binary code combined with the Monte Carlo (MC) simulation. The light curve solutions of both target systems required a cold starspot. The absolute parameters of the systems were calculated by using a <i>P</i> – <i>M</i> parameter relationship. The positions of the systems were also depicted on the Hertzsprung-Russell (HR), <i>P</i> - <i>L</i>, log<i>M</i>_tot - log<i>J</i>₀, and <i>T</i> - <i>M</i> diagrams. The hotter component in both systems is determined to be a more massive star. Therefore, it can be concluded that both systems are W-type contact binary systems.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"299 - 315"},"PeriodicalIF":0.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443240","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 Diffuse Dwarfs in the Dynamically Cold Triple Galaxy Systems","authors":"I. D. Karachentsev,&nbsp;A. E. Nazarova,&nbsp;V. E. Karachentseva","doi":"10.1007/s10511-024-09832-3","DOIUrl":"10.1007/s10511-024-09832-3","url":null,"abstract":"<p>We report on the discovery of three large diffuse dwarf (LDD) galaxies located in isolated triple systems. They have effective diameters of 3.6 ÷ 10.0 kpc and effective surface brightness of 26.2 ÷ 27.3 ^m/sq. arcsec. We note that the LDD galaxies tend to occur in small groups with a very low dispersion of radial velocities. The total (orbital) mass of the triplets approximately equals to their integral stellar mass within velocity measurement errors. The presence of LDD galaxies in cold multiple systems seems mysterious.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"267 - 275"},"PeriodicalIF":0.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443236","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":"Probing Pseudoscalars with Pulsar Polarisation Data Sets","authors":"K. Chand,&nbsp;S. Mandal","doi":"10.1007/s10511-024-09833-2","DOIUrl":"10.1007/s10511-024-09833-2","url":null,"abstract":"<p>Recently a data set containing linear and circular polarisation information of a collection of six hundred pulsars has been released. The operative radio wavelength for the same was 21 cm. Pulsars radio emission process is modelled either with synchroton/superconducting self-Compton route or with curvature radiation route. These theories fall short of accounting for the circular polarisation observed, as they are predisposed towards producing, solely, linear polarisation. Here we invoke (pseudo)scalars and their interaction with photons mediated by colossal magnetic fields of pulsars, to account for the circular part of polarisation data. This enables us to estimate the pseudoscalar parameters such as its coupling to photons and its mass in conjunction as product. To obtain these values separately, we turn our attention to recent observation on 47 pulsars, whose absolute polarisation position angles have been made available. Except, a third of the latter set, the rest of it overlaps with the expansive former data set on polarisation type and degree. This helps us figure out, both the pseudoscalar parameters individually, that we report here.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"276 - 298"},"PeriodicalIF":0.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443238","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":"Reanalyzing the Light Curves and Absolute Parameters of Twenty Contact Binary Stars Using Tess Data","authors":"E. Paki,&nbsp;A. Poro","doi":"10.1007/s10511-024-09835-0","DOIUrl":"10.1007/s10511-024-09835-0","url":null,"abstract":"<p>Reanalyzing contact binaries with space-based photometric data and investigating possible parameter changes can yield accurate samples for theoretical studies. We investigated light curve solutions and fundamental parameters for twenty contact binary systems. The most recent Transiting Exoplanet Survey Satellite (TESS) data is used to analyze. The target systems in the investigation have an orbital period of less than 0.58 days. Light curve solutions were performed using the PHysics Of Eclipsing BinariEs (PHOEBE) Python code version 2.4.9. The results show that systems had various mass ratios from q = 0.149 to q = 3.915, fillout factors (the degree of contact) from f = 0.072 to f = 0.566, and inclinations from i = 52°.8 to i = 87°.3. The effective temperature of the stars was less than 7016 K, which was expected given the features of most contact binary stars. Twelve of the target systems' light curves were asymmetrical in the maxima, showing the O'Connell effect, and a starspot was required for light curve solutions. The estimation of the absolute parameters of the binary systems was presented using the a - P empirical relationship and discussed. The orbital angular momentum J₀ of the systems was calculated. The positions of the systems were also depicted on the M - L, M - R, q - L_ratio, M_tot - J₀, and T - M diagrams.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"316 - 329"},"PeriodicalIF":0.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443237","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":"A Simple Analytical Method Using Fokker-Planck Equation for Modeling Particle Acceleration At Astrophysical Shocks","authors":"J.-H. Ha","doi":"10.1007/s10511-024-09836-z","DOIUrl":"10.1007/s10511-024-09836-z","url":null,"abstract":"<p>Shocks are ubiquitous in astrophysical environments, and particle acceleration at such astrophysical shocks is related to high-energy phenomena. In particular, the acceleration mechanism and the time evolution of the particle distribution function have been extensively examined. This paper describes a simple analytic method using the one-dimensional Fokker-Planck equation in the test-particle regime. We aim to investigate the evolution of the particle distribution function in the shock upstream, which could be streaming toward Earth along the open magnetic field geometry. The behavior of the analytical solution is examined over a wide range of parameters representing shock structure, such as the shock Mach number, plasma beta, injection fraction into diffusive shock acceleration, and the scale of the upstream magnetic field. The behavior is associated with upstream turbulence for diffusive shock acceleration, as expected. Additionally, pre-accelerated particles could affect the time evolution of the particle distribution only when the radiative or advection losses are small enough for the pre-accelerated distribution to have a flatter power-law slope than the power-law slope based on shock acceleration theory. We also provide a formula for a spherically expanding shock and its relevant application to calculate high-energy emission due to hadronic interactions. We suggest that the simple analytic method could be applied to examine astrophysical shocks with a wide range of plasma parameters.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"330 - 347"},"PeriodicalIF":0.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443239","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":"Fermionic Vacuum Stresses in Models with Toroidal Compact Dimensions","authors":"A. A. Saharian,&nbsp;R. M. Avagyan,&nbsp;G. H. Harutyuynyan,&nbsp;G. H. Nikoghosyan","doi":"10.1007/s10511-024-09830-5","DOIUrl":"10.1007/s10511-024-09830-5","url":null,"abstract":"<p>We investigate vacuum expectation value of the energy-momentum tensor for a massive Dirac field in flat spacetime with a toroidal subspace of a general dimension. Quasiperiodicity conditions with arbitrary phases are imposed on the field operator along compact dimensions. These phases are interpreted in terms of magnetic fluxes enclosed by compact dimensions. The equation of state in the uncompact subspace is of the cosmological constant type. It is shown that, in addition to the diagonal components, the vacuum energy-momentum tensor has nonzero off-diagonal components. In special cases of twisted (antiperiodic) and untwisted (periodic) fields the off diagonal components vanish. For untwisted fields the vacuum energy density is positive and the energy-momentum tensor obeys the strong energy condition. For general values of the phases in the periodicity conditions the energy density and stresses can be either positive or negative. The numerical results are given for a Kaluza-Klein type model with two extra dimensions.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 2","pages":"231 - 245"},"PeriodicalIF":0.6,"publicationDate":"2024-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141942461","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":"Viscous Plane Symmetric String Cosmological Model in f (R) Gravity","authors":"A. Dabre,&nbsp;Pallavi Makode","doi":"10.1007/s10511-024-09826-1","DOIUrl":"10.1007/s10511-024-09826-1","url":null,"abstract":"<p>In this paper, we have used the Plane Symmetric LRS Bianchi type I metric to study bulk viscous fluid coupled to a string of clouds within the framework of the <i>f</i> (<i>R</i>) theory of gravity. To obtain the deterministic solutions, some physically plausible conditions like the weak field limit for a point-like source <i>f</i> (<i>R</i>) = <i>R</i> ^3/2 , the very well known expansion-shear scalar proportionality relation and the special form of an average scale factor are taken into account. Furthermore, we have calculated some physical and kinematical parameters along with the energy conditions to study the astrophysical implications of the constructed model and discussed their graphical behaviour, which shows good similarity with recent observational data.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 2","pages":"161 - 177"},"PeriodicalIF":0.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869723","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":"Re-Examining Berman’s Parametrization of the Hubble Parameter in the Context of Late-Time Acceleration","authors":"K. R. Mishra,&nbsp;R. Kumar,&nbsp;S. K. J. Pacif","doi":"10.1007/s10511-024-09831-4","DOIUrl":"10.1007/s10511-024-09831-4","url":null,"abstract":"<p>In this paper, we have revisited the Berman’s idea of the variation of Hubble parameter. While previously explored in the context of Λ-varying cosmologies, where scale factor variations yield linear universe expansion, this parametrization has undergone extensive scrutiny. Our investigation, however, explores into its implications in the context of late-time cosmic acceleration, within the framework of classical general relativity, adopting the Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime as our background metric. Our analysis offers a precise solution to Einstein’s field equations (EFEs) in a model-independent way, affording a thorough assessment of both geometrical and physical model parameters. Additionally, this study supplements its findings with graphical representations of the evolving cosmological parameters across flat, closed, and open universe scenarios, all subject to constraints derived from the model parameters. In synthesizing these results, we shed light on the intricate interplay between cosmic acceleration, dark energy, and the parametrization of the Hubble parameter, thereby providing valuable insights into the fundamental mechanics of our universe.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 2","pages":"246 - 265"},"PeriodicalIF":0.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869724","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":"Activity of the Spectral Class K2V Dwarf HD 189733 in a Hot-Jupiter Type Exoplanet","authors":"I. S. Savanov","doi":"10.1007/s10511-024-09824-3","DOIUrl":"10.1007/s10511-024-09824-3","url":null,"abstract":"<p>Results are presented from an analysis of manifestations of the activity of the spectral class K2V dwarf HD189733, which has one of the best studied exoplanets of the hot-Jupiter type. Including the activity of the star makes analysis of the characteristics of the planet considerably more complicated (in particular, cool spots on the star’s surface introduce an additional signal in the relation between the depth of a transit and the size of the planet and prevent an exact determination of the radius of the planet). Photometric data for HD189733 in the archive of the TESS mission are analyzed and conclusions are reached on the values of the rotation period P_rot of the star, for which we estimated values of 12.5 and 11.3 days for sectors 41 and 54, respectively. A comparison of these with previous estimates based on earthbound photometric observations suggests that the differences in P_rot at different times are related to the fact of different observation times spots located at different latitudes on the surface of the differentially rotating star predominated. According to the TESS data the amplitude of the brightness variation of HD189733 is 1.6 and 0.9% of the mean brightness level of the star (for sectors 41 and 54, respectively). The standard method was used to estimate the spottedness parameter of the star (2.0 and 1.2% of the star’s surface area) and values of the area of the spotted surface A of the star in absolute terms (9200 MSH and 5400 MSH for sectors 41 and 54, respectively) were obtained. Based on 771 estimates of the star’s brightness in the V band presented in the Kamogata Wide-field Survey, an analysis was made of the long-term activity of HD189733 which yielded indications of the possible existence of activity cycles of duration 1140 and 4220 days (3.1 and 11.6 years, respectively). Based on an analysis of published data it has been concluded that the level of chromospheric activity of HD189733 exceeds the average values typical of other cool dwarfs with analogous values of the color index (B-V) and is higher than the solar value. It is concluded that HD189733 has a moderate (or somewhat higher than average) activity typical of analogous dwarfs in spectral class K but, nevertheless, requires that the properties and evolution of the planet formed around this star be taken into detailed account during modeling, regardless of whether a simplified method or an exact magnetohydrodynamic model is used to estimate them. It should also be noted that the activity of the star is a variable over time (on a time scale comparable to P_rot) and requires estimates that are made simultaneously with the main studies of the exoplanet’s atmosphere.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 2","pages":"140 - 148"},"PeriodicalIF":0.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869722","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":"Classification of BLL Blazars by Optical Activity Types","authors":"A. M. Mickaelian,&nbsp;H. V. Abrahamyan,&nbsp;G. M. Paronyan,&nbsp;G. A. Mikayelyan,&nbsp;A. G. Sukiasyan,&nbsp;V. K. Mkrtchyan","doi":"10.1007/s10511-024-09822-5","DOIUrl":"10.1007/s10511-024-09822-5","url":null,"abstract":"<p>We have carried out a spectral classification by the Activity Types for a subsample of Blazars from the BZCAT v.5 Catalogue, namely the BL Lac (BLL, Lacertids) candidates, designated in the Catalogue as BZB subtype objects. The classification is based on the Sloan Digital Sky Survey (SDSS) homogeneous medium-resolution optical spectroscopy and along with the standard BPT-type diagnostic diagrams, we have applied our newly introduced fine classification scheme with subtypes of Quasars and considering many more features. Out of 1151 BZB objects, 552 having SDSS spectra were classified. After new classification, 259 (46.1%) of 552 have not changed their optical class, and 293 (53.1%) of these objects have changed their optical class. Having this new information on the optical classification we suggest to change the classification of some objects in BZCAT: for 130 BZB objects to BZG, for 18 BZB objects to BZQ and for 145 BZB objects to BZU.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 2","pages":"119 - 127"},"PeriodicalIF":0.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141869725","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}