Universe最新文献_第4页

Stellar Modeling via the Tolman IV Solution: The Cases of the Massive Pulsar J0740+6620 and the HESS J1731-347 Compact Object 通过托尔曼 IV 解决方案建立恒星模型：大质量脉冲星J0740+6620和HESS J1731-347紧凑天体的案例

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-27 DOI: 10.3390/universe10090342

Grigoris Panotopoulos

{"title":"Stellar Modeling via the Tolman IV Solution: The Cases of the Massive Pulsar J0740+6620 and the HESS J1731-347 Compact Object","authors":"Grigoris Panotopoulos","doi":"10.3390/universe10090342","DOIUrl":"https://doi.org/10.3390/universe10090342","url":null,"abstract":"We model compact objects of known stellar mass and radius made of isotropic matter within Einstein’s gravity. The interior solution describing hydrostatic equilibrium we are using throughout the manuscript corresponds to the Tolman IV exact analytic solution obtained a long time ago. The three free parameters of the solutions are determined by imposing the matching conditions for objects of known stellar mass and radius. Finally, using well established criteria, it is shown that, contrary to the Kohler Chao solution, the Tolman IV solution is compatible with all requirements for well-behaved and realistic solutions, except for the relativistic adiabatic index that diverges at the surface of stars. The divergence of the index Γ may be resolved, including a thin crust assuming a polytropic equation of state, which is precisely the case seen in studies of neutron stars. To the best of our knowledge, we model here for the first time the recently discovered massive pulsar PSR J0740+6620 and the strangely light HESS compact object via the Tolman IV solution. The present work may be of interest to model builders as well as a useful reference for future research.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"44 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210907","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

Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe 欧洲上空行星际日冕物质抛射（ICME）和同向相互作用区（CIR）驱动的地磁暴期间的电离层测量比较

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-27 DOI: 10.3390/universe10090344

Kitti Alexandra Berényi, Loredana Perrone, Dario Sabbagh, Carlo Scotto, Alessandro Ippolito, Árpád Kis, Veronika Barta

{"title":"Ionosonde Measurement Comparison during an Interplanetary Coronal Mass Ejection (ICME)- and a Corotating Interaction Region (CIR)-Driven Geomagnetic Storm over Europe","authors":"Kitti Alexandra Berényi, Loredana Perrone, Dario Sabbagh, Carlo Scotto, Alessandro Ippolito, Árpád Kis, Veronika Barta","doi":"10.3390/universe10090344","DOIUrl":"https://doi.org/10.3390/universe10090344","url":null,"abstract":"A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16–20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h’F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N2 ratio.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"188 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227846","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

Modeling the TESS Light Curve of Ap Si Star MX TrA 模拟弧矽星 MX TrA 的 TESS 光曲线

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-26 DOI: 10.3390/universe10090341

Yury Pakhomov, Ilya Potravnov, Anna Romanovskaya, Tatiana Ryabchikova

引用次数: 0

Source Count Distribution of Fermi LAT Gamma-Ray Blazars Using Novel Nonparametric Methods 使用新型非参数方法研究费米 LAT 伽马射线耀斑星的源计数分布

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-26 DOI: 10.3390/universe10090340

Xuhang Yin, Houdun Zeng

引用次数: 0

Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV—Catalog of Cataclysmic Variables from the First 3-yr Survey 利用 TMTS 对 LAMOST 星场进行的分钟级观测：IV-来自首次三年巡天的大灾变变星目录

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-23 DOI: 10.3390/universe10090337

Qichun Liu, Jie Lin, Xiaofeng Wang, Zhibin Dai, Yongkang Sun, Gaobo Xi, Jun Mo, Jialian Liu, Shengyu Yan, Alexei V. Filippenko, Thomas G. Brink, Yi Yang, Kishore C. Patra, Yongzhi Cai, Zhihao Chen, Liyang Chen, Fangzhou Guo, Xiaojun Jiang, Gaici Li, Wenxiong Li, Weili Lin, Cheng Miao, Xiaoran Ma, Haowei Peng, Qiqi Xia, Danfeng Xiang, Jicheng Zhang

{"title":"Minute-Cadence Observations of the LAMOST Fields with the TMTS: IV—Catalog of Cataclysmic Variables from the First 3-yr Survey","authors":"Qichun Liu, Jie Lin, Xiaofeng Wang, Zhibin Dai, Yongkang Sun, Gaobo Xi, Jun Mo, Jialian Liu, Shengyu Yan, Alexei V. Filippenko, Thomas G. Brink, Yi Yang, Kishore C. Patra, Yongzhi Cai, Zhihao Chen, Liyang Chen, Fangzhou Guo, Xiaojun Jiang, Gaici Li, Wenxiong Li, Weili Lin, Cheng Miao, Xiaoran Ma, Haowei Peng, Qiqi Xia, Danfeng Xiang, Jicheng Zhang","doi":"10.3390/universe10090337","DOIUrl":"https://doi.org/10.3390/universe10090337","url":null,"abstract":"The Tsinghua University–Ma Huateng Telescopes for Survey (TMTS) started to monitor the LAMOST plates in 2020, leading to the discovery of numerous short-period eclipsing binaries, peculiar pulsators, flare stars, and other variable objects. Here, we present the uninterrupted light curves for a sample of 64 cataclysmic variables (CVs) observed/discovered using the TMTS during its first three-year observations, and we introduce new CVs and new light-variation periods (from known CVs) revealed through the TMTS observations. Thanks to the high-cadence observations of TMTS, diverse light variations, including superhumps, quasi-periodic oscillations, large-amplitude orbital modulations, and rotational modulations, are able to be detected in our CV samples, providing key observational clues for understanding the fast-developing physical processes in various CVs. All of these short-timescale light-curve features help further classify the subtypes of CV systems. We highlight the light-curve features observed in our CV sample and discuss further implications of minute-cadence light curves for CV identifications and classifications. Moreover, we examine the Hα emission lines in the spectra from our nonmagnetic CV samples (i.e., dwarf novae and nova-like subclasses) and find that the distribution of Hα emission strength shows significant differences between the sources with orbital periods above and below the period gap, which agrees with the trend seen from the SDSS nonmagnetic CV sample.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"2 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210920","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

Hybrid Isentropic Twin Stars 混合等熵双星

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-23 DOI: 10.3390/universe10090336

Juan Pablo Carlomagno, Gustavo A. Contrera, Ana Gabriela Grunfeld, David Blaschke

{"title":"Hybrid Isentropic Twin Stars","authors":"Juan Pablo Carlomagno, Gustavo A. Contrera, Ana Gabriela Grunfeld, David Blaschke","doi":"10.3390/universe10090336","DOIUrl":"https://doi.org/10.3390/universe10090336","url":null,"abstract":"We present a study of hybrid neutron stars with color superconducting quark matter cores at a finite temperature that results in sequences of stars with constant entropy per baryon, s/nB=const. For the quark matter equation of state, we employ a recently developed nonlocal chiral quark model, while nuclear matter is described with a relativistic density functional model of the DD2 class. The phase transition is obtained through a Maxwell construction under isothermal conditions. We find that traversing the mixed phase on a trajectory at low s/nB≲2 in the phase diagram shows a heating effect, while at larger s/nB the temperature drops. This behavior may be attributed to the presence of a color superconducting quark matter phase at low temperatures and the melting of the diquark condensate which restores the normal quark matter phase at higher temperatures. While the isentropic hybrid star branch at low s/nB≲2 is connected to the neutron star branch, it becomes disconnected at higher entropy per baryon so that the “thermal twin” phenomenon is observed. We find that the transition from connected to disconnected hybrid star sequences may be estimated with the Seidov criterion for the difference in energy densities. The radii and masses at the onset of deconfinement exhibit a linear relationship and thus define a critical compactness of the isentropic star configuration for which the transition occurs and which, for large enough s/nB≳2 values, is accompanied by instability. The results of this study may be of relevance for uncovering the conditions for the supernova explodability of massive blue supergiant stars using the quark deconfinement mechanism. The accretion-induced deconfinement transition with thermal twin formation may contribute to explaining the origin of eccentric orbits in some binary systems and the origin of isolated millisecond pulsars.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"90 4 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210910","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

Gravitational Particle Production and the Hubble Tension 引力粒子产生与哈勃张力

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-23 DOI: 10.3390/universe10090338

Recai Erdem

引用次数: 0

Energy-Momentum Squared Gravity: A Brief Overview 能量-动量平方引力：简要概述

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-23 DOI: 10.3390/universe10090339

Ricardo A. C. Cipriano, Nailya Ganiyeva, Tiberiu Harko, Francisco S. N. Lobo, Miguel A. S. Pinto, João Luís Rosa

{"title":"Energy-Momentum Squared Gravity: A Brief Overview","authors":"Ricardo A. C. Cipriano, Nailya Ganiyeva, Tiberiu Harko, Francisco S. N. Lobo, Miguel A. S. Pinto, João Luís Rosa","doi":"10.3390/universe10090339","DOIUrl":"https://doi.org/10.3390/universe10090339","url":null,"abstract":"In this work, we present a review of Energy-Momentum Squared Gravity (EMSG)—more specifically, f(R,TμνTμν) gravity, where R represents the Ricci scalar and Tμν denotes the energy-momentum tensor. The inclusion of quadratic contributions from the energy-momentum components has intriguing cosmological implications, particularly during the Universe’s early epochs. These effects dominate under high-energy conditions, enabling EMSG to potentially address unresolved issues in General Relativity (GR), such as the initial singularity and aspects of big-bang nucleosynthesis in certain models. The theory’s explicit non-minimal coupling between matter and geometry leads to the non-conservation of the energy-momentum tensor, which prompts the investigation of cosmological scenarios through the framework of irreversible thermodynamics of open systems. By employing this formalism, we interpret the energy-balance equations within EMSG from a thermodynamic perspective, viewing them as descriptions of irreversible matter creation processes. Since EMSG converges to GR in a vacuum and differences emerge only in the presence of an energy-momentum distribution, these distinctions become significant in high-curvature regions. Therefore, deviations from GR are expected to be pronounced in the dense cores of compact objects. This review delves into these facets of EMSG, highlighting its potential to shed light on some of the fundamental questions in modern cosmology and gravitational theory.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"11 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210912","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

A Study of the Accretion–Jet Coupling of Black Hole Objects at Different Scales 不同尺度黑洞天体的吸积-喷流耦合研究

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-22 DOI: 10.3390/universe10080335

Zhou Yang, Qing-Chen Long, Wei-Jia Yang, Ai-Jun Dong

{"title":"A Study of the Accretion–Jet Coupling of Black Hole Objects at Different Scales","authors":"Zhou Yang, Qing-Chen Long, Wei-Jia Yang, Ai-Jun Dong","doi":"10.3390/universe10080335","DOIUrl":"https://doi.org/10.3390/universe10080335","url":null,"abstract":"The fundamental plane of black hole activity is a very important tool to study accretion and jets. However, we found that the SEDs of AGNs and XRBs are different in the 2–10 keV energy band, and it seems inappropriate to use 2–10 keV X-ray luminosities to study the fundamental plane. In this work, we use the luminosity near the peak of the blackbody radiation of the active galactic nuclei and black hole binaries to replace the 2–10 keV luminosity. We re-explore the fundamental plane of black hole activity by using the 2500 A˚ luminosity as the peak luminosity of the blackbody radiation of AGNs and 1 keV luminosity as the peak luminosity of the blackbody radiation of XRBs. We compile samples of black hole binaries and active galactic nuclei with luminosity near the peak luminosity of blackbody radiation and study the fundamental plane between radio luminosity (LR), the peak luminosity of blackbody radiation (Lpeak), and black hole mass (MBH). We find that the radio–peak luminosity correlations are L5GHz/LEdd∝(L2500A˚/LEdd)1.55 and L5GHz/LEdd∝(L1keV/LEdd)1.53 for AGN and XRB, respectively, in the radiatively efficient sample, and L5GHz/LEdd∝(L2500A˚/LEdd)0.48 and L5GHz/LEdd∝(L1keV/LEdd)0.53 in the radiatively inefficient sample, respectively. Based on the similarities in radio–peak correlations, we further propose a fundamental plane in radio luminosity, the peak luminosity of blackbody radiation, and black hole mass, which is radiatively efficient: logL5GHz=1.57−0.01+0.01logLpeak−0.32−0.16+0.16logMBH−27.73−0.34+0.34 with a scatter of σR = 0.48 dex, and radiatively inefficient: logL5GHz=0.45−0.01+0.01logLpeak+0.91−0.10+0.12logMBH+12.58−0.38+0.38 with a scatter of σR = 0.63 dex. Our results are similar to those of previous studies on the fundamental plane for radiatively efficient and radiatively inefficient black hole activity. However, our results exhibit a smaller scatter, so when using the same part of blackbody radiation (i.e., the peak luminosity of the blackbody radiation), the fundamental plane becomes a little bit tighter.","PeriodicalId":48646,"journal":{"name":"Universe","volume":"10 1","pages":""},"PeriodicalIF":2.9,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142210916","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

Slow Body MHD Waves in Inhomogeneous Photospheric Waveguides 非均质光层波导中的慢体 MHD 波

IF 2.9 4区物理与天体物理

Universe Pub Date : 2024-08-21 DOI: 10.3390/universe10080334

Istvan Ballai, Fisal Asiri, Viktor Fedun, Gary Verth, Emese Forgács-Dajka, Abdulrahman B. Albidah

引用次数: 0