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Determining the Frequency Function of Flares and Starspot Coverage in Active Flare Stars Discovered by the Kepler Mission 确定由开普勒任务发现的活跃耀斑恒星的耀斑频率函数和星斑覆盖
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09847-4
A. A. Akopian
{"title":"Determining the Frequency Function of Flares and Starspot Coverage in Active Flare Stars Discovered by the Kepler Mission","authors":"A. A. Akopian","doi":"10.1007/s10511-025-09847-4","DOIUrl":"10.1007/s10511-025-09847-4","url":null,"abstract":"<p>Based on data from the Kepler orbital observatory, this study investigates the most active flare stars, which exhibited 250 or more flares during the Kepler mission period. The main research objectives were: (a) analyzing light curves to identify unique physical characteristics of individual stars; (b) defining the periodic/cyclic flare frequency function (PFFF) of flare stars, associated with axial/orbital rotations; and (c) presenting a novel method for determining starspot coverage using the PFFF and applying this method. The study produced corresponding PFFF values with periodicities close to the star rotation periods. Expected phase distributions of flares were constructed and compared with observed flare distributions for the given rotation period. For all stars examined, this comparison (using the χ<sup>2</sup> criterion) supports the periodicity of flare frequency. It is hypothesized that the starspot distribution of flare stars can be represented by the von Mises circular distribution, with parameters derived from the respective flare frequency function. Estimates of the starspot coverage for the stars studied were obtained.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"487 - 505"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108758","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}
引用次数: 0
Dark Matter in the Presence of Dark Energy 暗能量存在下的暗物质
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09848-3
H. A. Harutyunian
{"title":"Dark Matter in the Presence of Dark Energy","authors":"H. A. Harutyunian","doi":"10.1007/s10511-025-09848-3","DOIUrl":"10.1007/s10511-025-09848-3","url":null,"abstract":"<p>The article considers the issue of changes in the total energy of baryonic objects and their systems in the presence of dark energy, whose carrier, by definition, interacts with all baryonic objects. It is emphasized that dark energy was discovered due to such interaction that accelerates the universe’s expansion. Since dark energy (dark energy carrier) is uniformly distributed, the physical consequences of interaction between the dark energy carrier and baryonic matter are considered at all hierarchical levels of baryonic structures. Drawing on the second law of thermodynamics, the author concludes that under the effect of dark energy, the energy of all baryonic systems gradually increases and their stability declines while the virial value becomes positive and continues to grow for any structures considered to be stable. A similar analysis performed for atomic nuclei reveals that over time, nuclear binding energy decreases, nuclear stability declines, and the nuclear mass increases. This effect gives a new perspective on Ambartsumian’s hypothesis about the existence of superdense matter clumps in the nuclei of stars and galaxies and enables its new interpretation.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"506 - 519"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108766","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}
引用次数: 0
Domain Wall Bianchi Type VI0 Universe in f(R, T) Gravity 域壁Bianchi型VI0宇宙在f（R， T）引力
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09850-9
S. P. Hatkar, D. P. Tadas, S. D. Katore
{"title":"Domain Wall Bianchi Type VI0 Universe in f(R, T) Gravity","authors":"S. P. Hatkar,&nbsp;D. P. Tadas,&nbsp;S. D. Katore","doi":"10.1007/s10511-025-09850-9","DOIUrl":"10.1007/s10511-025-09850-9","url":null,"abstract":"<p>We consider the Bianchi type-VI<sub>0</sub> space time with domain walls in the framework of the modified f (R, T) theory of gravitation. To solve the field equations, we assume that the shear scalar σ is proportional to the expansion scalar θ. We also consider the parametrization of the equation of the state parameter of barotropic fluid and discuss the effect on domain walls. It has been observed that the domain wall may behave like dark energy. Some physical parameters are also discussed in detail.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"537 - 555"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108764","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}
引用次数: 0
Thermodynamics and its Quantum Correction of Vacuum Nonsingular Black Hole 真空非奇异黑洞的热力学及其量子修正
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09851-8
D. Ma, T. Huo, C. Liu
{"title":"Thermodynamics and its Quantum Correction of Vacuum Nonsingular Black Hole","authors":"D. Ma,&nbsp;T. Huo,&nbsp;C. Liu","doi":"10.1007/s10511-025-09851-8","DOIUrl":"10.1007/s10511-025-09851-8","url":null,"abstract":"<p>This paper investigates the thermodynamic properties of vacuum nonsingular black holes. Considering the energy characteristics of the regularity spacetime, we use the modified first law of black hole thermodynamics to calculate the black holes' Hawking temperature, entropy and heat capacity. The obtained temperature is the same as that obtained by the surface gravity and tunneling methods. Also, the entropy is satisfied with the Bekenstein-Hawking area law. Notably, the heat capacity of large-mass black holes diverges, while that of small-mass black holes tends to zero, with a phase transition point existing. Additionally, we consider the quantum gravity effect by using the generalized uncertainty principle to study the quantum corrections of the thermodynamic properties for the vacuum nonsingular black holes. The generalized uncertainty principle introduces a logarithmic correction term to the black hole entropy. Also, the temperature and heat capacity are modified.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"556 - 570"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108763","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}
引用次数: 0
Modified Finch and Skea Stellar Model in Higher Dimensions 改进的高维Finch和Skea恒星模型
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2025-01-17 DOI: 10.1007/s10511-025-09852-7
A. Jangid, S. Das, B. S. Ratanpal, K. K. Venkataratnam
{"title":"Modified Finch and Skea Stellar Model in Higher Dimensions","authors":"A. Jangid,&nbsp;S. Das,&nbsp;B. S. Ratanpal,&nbsp;K. K. Venkataratnam","doi":"10.1007/s10511-025-09852-7","DOIUrl":"10.1007/s10511-025-09852-7","url":null,"abstract":"<p>Within the framework of higher dimensions, we enhance the model of Pandya and Thomas and assume that the system is anisotropic in the Finch and Skea ansatz. Our model explores various physical parameters in higher dimensions, including mass, energy density, radial and transverse pressures, and the anisotropy factor. We have used graphical technique to analyse the energy conditions, equilibrium conditions, and stability across different dimensions. Furthermore, the mass of a particular compact object have shown to increase with radial parameter as space-time dimensions increase. Additionally, by generating a mass-radius (<i>M</i>-<i>R</i>) plot, we demonstrate the influence of dimensional factor on the maximum mass and radius allowed by our toy model.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 4","pages":"571 - 586"},"PeriodicalIF":0.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108762","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}
引用次数: 0
Escape Probability and Average Numbers of Photon Scattering Events. II. Monochromatic Isotropic Scattering in a One-Dimensional Medium and Plane Media 光子散射事件的逃逸概率和平均数量。II.一维介质和平面介质中的单色各向同性散射
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09839-w
D. I. Nagirner, A. V. Dementyev, E. V. Volkov
{"title":"Escape Probability and Average Numbers of Photon Scattering Events. II. Monochromatic Isotropic Scattering in a One-Dimensional Medium and Plane Media","authors":"D. I. Nagirner,&nbsp;A. V. Dementyev,&nbsp;E. V. Volkov","doi":"10.1007/s10511-024-09839-w","DOIUrl":"10.1007/s10511-024-09839-w","url":null,"abstract":"<p>As examples of applying the formulas from part I we examine scattering in a one-dimensional medium for which all the characteristics of the radiative field are expressed in terms of elementary functions and (three-dimensional) isotropic monochromatic scattering. Some properties of the Ambartsumyan function are studied and the asymptotes of the average numbers of photon scattering events in an optically thick plane layer are derived.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"375 - 404"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443242","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}
引用次数: 0
Lorentzian Correction for the Evolution of the CMB Temperature 对 CMB 温度演变的洛伦兹修正
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09837-y
A. Novais, A. L. B. Ribero
{"title":"Lorentzian Correction for the Evolution of the CMB Temperature","authors":"A. Novais,&nbsp;A. L. B. Ribero","doi":"10.1007/s10511-024-09837-y","DOIUrl":"10.1007/s10511-024-09837-y","url":null,"abstract":"<p>Observational evidence consistently shows that the universe is spatially flat and undergoes Lorentzian time dilation as a function of redshift. In combination, such discoveries suggest that a Minkowskian description of cosmology might be technically viable. The thermal evolution that transpires in a conformal spacetime is herein derived. The description is constrained by the energy conservation of a unified cosmic fluid. The resulting model puts forth a Lorentzian correction for the temperature of the CMB as a function of redshift, which improves current data fitting without adding any free parameter. Furthermore, it sheds light upon the early galaxy formation problem: our model predicts up to 0.86 Gyr older objects within the first two billion years of the structure evolution in the universe.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"348 - 363"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443243","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}
引用次数: 0
Plane Symmetric Gravitational Fields in (D+1)-dimensional General Relativity D+1）维广义相对论中的平面对称引力场
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09840-3
R. M. Avagyan, T. A. Petrosyan, A. A. Saharian, G. H. Harutyunyan
{"title":"Plane Symmetric Gravitational Fields in (D+1)-dimensional General Relativity","authors":"R. M. Avagyan,&nbsp;T. A. Petrosyan,&nbsp;A. A. Saharian,&nbsp;G. H. Harutyunyan","doi":"10.1007/s10511-024-09840-3","DOIUrl":"10.1007/s10511-024-09840-3","url":null,"abstract":"<p>We consider plane symmetric gravitational fields within the framework of General Relativity in (D+1)-dimensional spacetime. Two classes of vacuum solutions correspond to higher-dimensional generalizations of the Rindler and Taub spacetimes. The general solutions are presented for a positive and negative cosmological constant as the only source of the gravity. Matching conditions on a planar boundary between two regions with distinct plane symmetric metric tensors are discussed. An example is considered with Rindler and Taub geometries in neighboring half-spaces. As another example, we discuss a finite thickness cosmological constant slab embedded into the Minkowski, Rindler and Taub spacetimes. The corresponding surface energy-momentum tensor is found required for matching the exterior and interior geometries.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"405 - 419"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443246","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}
引用次数: 0
Methanimine in Cool Cosmic Objects Using Accurate Collisional Rate Coefficients 利用精确的碰撞率系数研究冷宇宙天体中的甲烷化物
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09838-x
S. Chandra, M. K. Sharma
{"title":"Methanimine in Cool Cosmic Objects Using Accurate Collisional Rate Coefficients","authors":"S. Chandra,&nbsp;M. K. Sharma","doi":"10.1007/s10511-024-09838-x","DOIUrl":"10.1007/s10511-024-09838-x","url":null,"abstract":"<p>Accurate collisional rate coefficients for collisional transitions between 15 rotational levels of methanimine, colliding with p-H<sub>2</sub> molecule, are available. Methanimine is a planar, asymmetric top molecule having electric dipole moment with components μ<sub><i>a</i></sub> = 1.3396 Debye and μ<sub><i>b</i></sub> = 1.4461 Debye, and thus, producing both the a and b type spectral lines of nearly equal intensities. Therefore, all the rotational levels need to be considered together. Between 15 rotational levels, 105 collisional transitions are considered in an investigation by others. We have discussed that each level is not connected with all others through the collisions, and therefore, there should be 77 instead of 105 collisional transitions between 15 levels of methanimine. With availability of accurate collisional rate coefficients, it is worth to perform the Sobolev analysis of methanimine. We have found six weak MASER transitions, 1<sub>10</sub>-1<sub>11</sub>, 2<sub>11</sub>-2<sub>12</sub>, 3<sub>12</sub>-3<sub>13</sub>, 4<sub>1.3</sub>-4<sub>1.4</sub>, 3<sub>03</sub>-2<sub>12</sub> and 4<sub>0.4</sub>-3<sub>1.3</sub>, and one transition 1<sub>11</sub>-2<sub>02</sub>, showing anomalous absorption. These seven lines may play important role for the methanimine.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"364 - 374"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443245","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}
引用次数: 0
Thermodiffusion Unipolar Electric Generator 热扩散单极发电机
IF 0.6 4区 物理与天体物理
Astrophysics Pub Date : 2024-10-14 DOI: 10.1007/s10511-024-09841-2
G. S. Bisnovatyi-Kogan, M. V. Glushikhina
{"title":"Thermodiffusion Unipolar Electric Generator","authors":"G. S. Bisnovatyi-Kogan,&nbsp;M. V. Glushikhina","doi":"10.1007/s10511-024-09841-2","DOIUrl":"10.1007/s10511-024-09841-2","url":null,"abstract":"<p>A model of a conducting cylinder with a radial temperature gradient which creates an electric field that increases with time in the surrounding vacuum is examined. The conditions under which this model functions are pointed out. An electric field is also generated when a magnetic field exists along the axis of the cylinder. This article discusses the interactions of the thermal flux, magnetic field, and charge distribution. Four models are considered with different conditions for the supply of electrons from a central source and the possibility either of capturing electrons inside the cylinder or their freely leaving it through the outer boundary.</p>","PeriodicalId":479,"journal":{"name":"Astrophysics","volume":"67 3","pages":"420 - 431"},"PeriodicalIF":0.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142443244","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}
引用次数: 0
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