New Astronomy最新文献

{"title":"Radiation pressure and galactic cosmic rays-driven gravitational instability in rotating and magnetized viscoelastic fluids","authors":"Joginder Singh Dhiman,&nbsp;Mehak Mahajan","doi":"10.1016/j.newast.2024.102251","DOIUrl":"10.1016/j.newast.2024.102251","url":null,"abstract":"<div><p>This paper studies the combined effects of radiation and galactic cosmic ray pressures on the gravitational instability of magnetized and rotating viscoelastic fluids. The dispersion relations are derived using the normal mode analysis and discussed in the hydrodynamic (weakly coupled fluid) and kinetic (strongly coupled fluid) limits. These dispersion relations are analyzed separately for transverse and longitudinal wave propagation modes. Jeans instability criteria are obtained for kinetic and hydrodynamic limits for both modes of wave propagation, and it is found that the critical Jeans wavenumbers in each case are modified due to the presence of viscoelastic effects, radiation and cosmic rays pressures, and Alfvên wave velocity. It is also observed that the radiation pressure, cosmic ray pressure and viscoelastic parameters suppress the growth rate and thus have stabilizing effects on the Jeans instability. However, cosmic ray diffusion has a destabilizing effect on the onset of gravitational instability. The effects of various parameters on the growth rate of instability are calculated numerically and the outcomes are depicted graphically. The results of the present analysis shall be helpful in understanding the impact of cosmic rays and radiative mechanisms on the gravitational collapse in the viscoelastic region of molecular cloud clumps.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102251"},"PeriodicalIF":2.0,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141026716","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":"Nonlinearly charged black holes: Shadow and thin-accretion disk","authors":"Akhil Uniyal ,&nbsp;Sayan Chakrabarti ,&nbsp;Reggie C. Pantig ,&nbsp;Ali Övgün","doi":"10.1016/j.newast.2024.102249","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102249","url":null,"abstract":"<div><p>In this paper, we explore the effect of the parameters of non-linear electrodynamics (NLED) and magnetic charges on various aspects of black holes (BH) arising in the particular NLED theory. More precisely, we look into the behavior of photons around the BH and produce shadow by considering a thin accretion disk model. We initially examine the overall behavior of the photon sphere and the corresponding shadow silhouette under the effects of these parameters. Using the EHT data for Sgr. A* and M87*, we provide constraints on the magnetic charge <span><math><msub><mrow><mi>q</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span>. Our results indicate that M87* gives better constraints, and as the value of the NLED coupling parameter <span><math><mi>β</mi></math></span> is increased, the constrained range for <span><math><msub><mrow><mi>q</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span> widens. At lower values of <span><math><msub><mrow><mi>q</mi></mrow><mrow><mi>m</mi></mrow></msub></math></span>, we find that the shadow radius is close to the observed value. Then, we study different other aspects, such as the energy emitted by the accretion disk, the temperature of the disk around the BH, and the nature of light it gives off. We also look at how the black hole shadow appears in different situations. Finally, we investigate how the magnetic charge affects all the above mentioned aspects when we take into account NLED along with gravity. This study helps us understand the complex relationship between magnetic charge and its effect on various aspects related to a BH.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102249"},"PeriodicalIF":2.0,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140909802","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":"Does dynamical wormhole evolve from emergent scenario?","authors":"Dhritimalya Roy ,&nbsp;Ayanendu Dutta ,&nbsp;Bikram Ghosh ,&nbsp;Subenoy Chakraborty","doi":"10.1016/j.newast.2024.102248","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102248","url":null,"abstract":"<div><p>In the present work we analyze a dynamical wormhole solution with two fluids system (one isotropic and homogeneous and the other being inhomogeneous and anisotropic in nature) as the matter at the throat. We choose two different forms of Equation of State(EoS) and investigate two solutions of the wormhole geometry. The properties to ensure existence and traversability has been analyzed. Also, the model of the dynamic wormhole has been examined for a possibility of the Emergent Universe(EU) model in cosmological context. Finally, for the dynamical wormholes so obtained, Null Energy Condition(NEC) has been examined near the throat.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102248"},"PeriodicalIF":2.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140894097","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":"Three-dimensional stellar orbits due to off-centered dark matter halo at the center of the disc galaxies","authors":"Meenu Prajapati,&nbsp;Mamta Gulati","doi":"10.1016/j.newast.2024.102246","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102246","url":null,"abstract":"<div><p>Stellar orbits and the evolution of galaxies are intertwined processes that have long-term implications on each other. This paper studies how stellar orbits at the galaxy’s central region are disturbed by an asymmetric dark matter halo potential. Evidence from the observations and simulations in the Milky Way type galaxy suggests that the center of the dark matter halo could be off-centered by a few parsecs concerning the center of the core. The equations of motion of stars in the core of galaxies are expressed in terms of three-dimensional perturbed potential arising from the offset halo. The central region’s azimuthal variation in the effective potential is obtained and the first-order epicyclic theory is used to solve for the orbits. The magnitude of this perturbation potential grows at small radii and exhibits <span><math><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></math></span> azimuthal fluctuations. In the central region, within 3 kpc radius, even a small halo offset of 300 pc can cause a surprisingly strong spatial and kinematical lopsidedness. A planar orbit, initially assumed to be in disc plane, tends to leave the plane giving rise to non-planar configuration. Furthermore, as long as the halo offset persists, the central region will stay lopsided. The dark matter halo would significantly impact the dynamic development of this region and could help fuel the active galactic nucleus.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102246"},"PeriodicalIF":2.0,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140894096","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":"Escape from a rotating barred galaxy","authors":"Euaggelos E. Zotos ,&nbsp;Christof Jung","doi":"10.1016/j.newast.2024.102247","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102247","url":null,"abstract":"<div><p>We study the dynamics in the outer regions of a rotating barred galaxy and in particular, we observe the escape of a test particle from the gravitational potential of the galaxy. The acceleration mechanism of the test particle is a close encounter with one of the ends of the bar with the right relative phase of the position of the bar. This is a possible mechanism for the creation of high-velocity stars, i.e. stars with an energy sufficient to escape from the galaxy. Our results suggest that good candidates for high-velocity stars accelerated by this mechanism are the old low-mass high-velocity stars moving close to the disc. We will encounter the asymptotic dynamics which leads naturally to the study of a type of Poincaré map which can be reinterpreted as a scattering map. Thereby an iterated scattering map enters the picture in a quite natural form. The present work is a supplement to previous work on the dynamics in the inner region of the same model.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102247"},"PeriodicalIF":2.0,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140879440","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":"Exploring the physical properties of the γ Dor binary star RX Dra with photometry and asteroseismology","authors":"Ping Li,&nbsp;Wen-Ping Liao,&nbsp;Qi-Huan Zeng,&nbsp;Qi-Bin Sun,&nbsp;Min-Yu Li","doi":"10.1016/j.newast.2024.102234","DOIUrl":"10.1016/j.newast.2024.102234","url":null,"abstract":"&lt;div&gt;&lt;p&gt;We model the TESS light curve of the binary system RX Dra, and also first calculate a lot of theoretical models to fit the g-mode frequencies previously detected from the TESS series of this system. The mass ratio is determined to be &lt;span&gt;&lt;math&gt;&lt;mi&gt;q&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;=0.9026&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0032&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0032&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;. We newly found that there are 16 frequencies (F1–F7, F11–F20) identified as dipole g-modes, two frequencies (F21, F22) identified as quadrupole g-modes, and another two frequencies (F23, F24) identified as g-sextupole modes, based on these model fits. The primary star is newly determined to be a &lt;span&gt;&lt;math&gt;&lt;mi&gt;γ&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; Dor pulsator in the main-sequence stage with a rotation period of about 5.7&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;7&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; days, rotating slower than the orbital motion. The fundamental parameters of two components are firstly estimated as follows: &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;=1.53&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;17&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;00&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; M &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;= 1.38&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;00&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;18&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; M &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;=7240&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;44&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;490&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; K, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;T&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;=6747&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;221&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;201&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; K, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;=1.8288&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0959&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0260&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; R &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;= 1.3075&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;−&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;2543&lt;/mn&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;+&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0450&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; R &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/mrow&gt;&lt;","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102234"},"PeriodicalIF":2.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140791345","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":"f(R,A) gravity theory in Einstein space background and causality violation","authors":"Faizuddin Ahmed","doi":"10.1016/j.newast.2024.102245","DOIUrl":"10.1016/j.newast.2024.102245","url":null,"abstract":"<div><p>In this paper, we exploration a Petrov type-N vacuum solution to Einstein’s field equations, while incorporating a negative cosmological constant (<span><math><mrow><mi>Λ</mi><mo>&lt;</mo><mn>0</mn></mrow></math></span>) within the framework of modified gravity theories. This solution intriguingly accommodates closed time-like curves at a particular moment in time, effectively violates the causality condition, thus acts as a time-machine model. A key observation is that the determinant of the Ricci tensor <span><math><msup><mrow><mi>R</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow></msup></math></span> for this particular Einstein space metric differs from zero. This noteworthy finding suggests to the existence of an anti-curvature tensor defined <span><math><mrow><msup><mrow><mi>A</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow></msup><mo>=</mo><msubsup><mrow><mi>R</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msubsup></mrow></math></span> and hence, an anti-curvature scalar <span><math><mrow><mi>A</mi><mo>=</mo><msub><mrow><mi>g</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow></msub><mspace></mspace><msup><mrow><mi>A</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow></msup></mrow></math></span>, which is introduced with the Lagrangian of the system, thereby giving rise to as Ricci-inverse gravity theory. We consider <strong>class-I</strong> models of Ricci-inverse gravity, where the function <span><math><mrow><mi>f</mi><mo>=</mo><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>,</mo><mi>A</mi><mo>)</mo></mrow><mo>=</mo><mrow><mo>(</mo><mi>R</mi><mo>+</mo><mi>κ</mi><mspace></mspace><mi>A</mi><mo>)</mo></mrow></mrow></math></span> with <span><math><mi>κ</mi></math></span> is the coupling constant. We demonstrate that this Einstein space metric serves as a vacuum solution with a negative modified cosmological constant within the framework of Ricci-inverse gravity. Consequently, the violation of causality persists within this new gravity theory as well. Moreover, we solve the modified field equations by considering matter content other than vacuum and demonstrate that the energy-density and isotropic pressure satisfies the equation <span><math><mrow><mi>ρ</mi><mo>=</mo><mo>−</mo><mi>p</mi><mo>=</mo><mfrac><mrow><mn>3</mn><mspace></mspace><mi>κ</mi></mrow><mrow><mi>Λ</mi></mrow></mfrac></mrow></math></span>.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102245"},"PeriodicalIF":2.0,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140778925","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":"The improved component masses and parallaxes for the two close binary stars: HD 80671 and HD 97038","authors":"Suhail Masda","doi":"10.1016/j.newast.2024.102244","DOIUrl":"10.1016/j.newast.2024.102244","url":null,"abstract":"&lt;div&gt;&lt;p&gt;We present the fundamental stellar parameters, including the individual component masses, as well as the orbital parameters, and dynamical parallaxes of the two close binary stars; HD&lt;!--&gt; &lt;!--&gt;80671, and HD&lt;!--&gt; &lt;!--&gt;97038. The stellar parameters are spectrophotometrically estimated via Al-Wardat’s method for analyzing binary and multiple stellar systems, which is having a combination of the spectroscopic analysis and the photometric analysis to build the combined and individual synthetic spectral energy distributions of the individual components of the systems and so to estimate their fundamental parameters, metallicities, and ages. It employs Kurucz’s model atmospheres of single stars, while the orbital parameters are estimated using Tokovinin’s method. The individual spectrophotometric component masses are inferred with good accuracy, and found to be &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; = 1.47&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;10&lt;/mn&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;29&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;09&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; with an age of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;09&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; Gyr for HD&lt;!--&gt; &lt;!--&gt;80671, and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;A&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;17&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;09&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;h&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;B&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;12&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;08&lt;/mn&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;M&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mo&gt;⊙&lt;/mo&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; with an age of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;981&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;35&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; Gyr for HD&lt;!--&gt; &lt;!--&gt;97038. The improved dynamical parallaxes are given as &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mi&gt;y&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;28&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;305&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;45&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; mas for HD&lt;!--&gt; &lt;!--&gt;80671, and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;π&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;d&lt;/mi&gt;&lt;mi&gt;y&lt;/mi&gt;&lt;mi&gt;n&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;16&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;26&lt;/mn&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;30&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; mas for HD&lt;!--&gt; &lt;!--&gt;97038. The evolutionary status of two binaries is discussed depending on the positions of the compo","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102244"},"PeriodicalIF":2.0,"publicationDate":"2024-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140772694","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":"Resolving the pulsation contents of 13 δ Scuti stars with TESS and K2","authors":"Ai-Ying Zhou","doi":"10.1016/j.newast.2024.102235","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102235","url":null,"abstract":"<div><p>Using the <em>TESS</em> and <em>Kepler</em> K2 light curve archives, I have reanalyzed 13 known <span><math><mi>δ</mi></math></span> Scuti stars. AD Ari is now reclassified as a rotating ellipsoidal binary variable. EX Cnc and HD 73712 are reclassified as hybrid <span><math><mi>δ</mi></math></span> Sct-<span><math><mi>γ</mi></math></span> Dor pulsators. EX Cnc turns out to be an enticing asteroseismic target because of its three distinct groups of pulsation frequencies. The strong beating caused by two close frequencies is present in the star CD-54 7154. More than 71 pulsation frequencies were resolved for <span><math><mi>ι</mi></math></span> Boo and IT Dra with high significant levels, while V1821 Cyg, V2238 Cyg, BR Cnc, BU Cnc, and BV Cnc pulsate with a few dozen frequencies. In particular, K2 data revealed a significantly richer pulsational spectrum for the two <span><math><mi>δ</mi></math></span> Scuti stars BU Cnc and BV Cnc from six to 26. Unlike the other 12 stars, BN Cnc shows the simplest pulsation pattern. With high-precision and long-term space-based photometry, we are able to discern the pulsational contents of these stars more clearly and enhance our knowledge of them. This reanalysis using <em>TESS</em> and <em>Kepler</em> K2 data highlights the diversity of pulsational behavior among <span><math><mi>δ</mi></math></span> Scuti stars and the value of long-duration, high-precision photometry. Further asteroseismic modeling of these stars, particularly EX Cnc with its distinct frequency groups, promises to refine our understanding of their internal structures and pulsational mechanisms.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102235"},"PeriodicalIF":2.0,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140646292","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":"Particle motion around traversable wormholes: Possibility of closed timelike geodesics","authors":"Ayanendu Dutta ,&nbsp;Dhritimalya Roy ,&nbsp;Subenoy Chakraborty","doi":"10.1016/j.newast.2024.102236","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102236","url":null,"abstract":"<div><p>The present work investigates the general wormhole solution in Einstein gravity with an exponential shape function around an ultrastatic and a finite redshift geometry. The geodesic motion around the wormholes is studied in which the deflection angle of the orbiting photon sphere is found to be negative after a certain region, indicating the presence of repulsive effect of gravity in both the ultrastatic and finite redshift wormholes. Various unbounded and bounded timelike trajectories are presented on the wormhole embedding diagrams, in which some of the bound orbits involve intersection points that may lead to causality violating geodesics. Another class of closed timelike geodesics are obtained in the unstable circular trajectory that appeared at the wormhole throat. Finally, the trajectories are classified in terms of the family of CTG orbits.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"111 ","pages":"Article 102236"},"PeriodicalIF":2.0,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140605221","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}