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The size and shape dependence of the SDSS galaxy bispectrum SDSS星系双谱的大小和形状依赖性
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-08-10 DOI: 10.1016/j.newast.2024.102292
Anindita Nandi , Sukhdeep Singh Gill , Debanjan Sarkar , Abinash Kumar Shaw , Biswajit Pandey , Somnath Bharadwaj
{"title":"The size and shape dependence of the SDSS galaxy bispectrum","authors":"Anindita Nandi , Sukhdeep Singh Gill , Debanjan Sarkar , Abinash Kumar Shaw , Biswajit Pandey , Somnath Bharadwaj","doi":"10.1016/j.newast.2024.102292","DOIUrl":"10.1016/j.newast.2024.102292","url":null,"abstract":"<div><p>We have measured the spherically averaged bispectrum of the SDSS main galaxy sample, considering a volume-limited <span><math><msup><mrow><mrow><mo>[</mo><mn>296</mn><mo>.</mo><mn>75</mn><mspace></mspace><mi>Mpc</mi><mo>]</mo></mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> data cube with mean galaxy number density <span><math><mrow><mn>0</mn><mo>.</mo><mn>63</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mspace></mspace><msup><mrow><mi>Mpc</mi></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup></mrow></math></span> and median redshift <span><math><mrow><mn>0</mn><mo>.</mo><mn>102</mn></mrow></math></span>. Our analysis considers <span><math><mrow><mo>∼</mo><mn>1</mn><mo>.</mo><mn>37</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span> triangles, for which we have measured the binned bispectrum and analysed its dependence on the size and shape of the triangle. It spans wavenumbers <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo><mrow><mo>(</mo><mn>0</mn><mo>.</mo><mn>075</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>434</mn><mo>)</mo></mrow><mspace></mspace><msup><mrow><mi>Mpc</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span> for equilateral triangles, and a smaller range of <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> (the largest side) for triangles of other shapes. For all shapes, we find that the measured bispectrum is well modelled by a power law <span><math><mrow><mi>A</mi><mspace></mspace><msup><mrow><mrow><mo>(</mo><mrow><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>/</mo><mn>1</mn><mspace></mspace><msup><mrow><mi>Mpc</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow><mo>)</mo></mrow></mrow><mrow><mi>n</mi></mrow></msup></mrow></math></span>, where the best-fit values of <span><math><mi>A</mi></math></span> and <span><math><mi>n</mi></math></span> vary with the shape. The parameter <span><math><mi>A</mi></math></span> is the minimum for equilateral triangles and increases as the shape is deformed to linear triangles where the two largest sides are nearly aligned, reaching its maximum value for <span><math><mrow><mi>μ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>95</mn><mo>,</mo><mspace></mspace><mi>t</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>75</mn></mrow></math></span>. The values of <span><math><mi>n</mi></math></span> are all negative, <span><math><mrow><mo>|</mo><mi>n</mi><mo>|</mo></mrow></math></span> is minimum <span><math><mrow><mo>(</mo><mn>3</mn><mo>.</mo><mn>12</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>35</mn><mo>)</mo></mrow></math></span> for the shape bin <span><math><mrow><mi>μ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>65</mn><mo>,</mo><mspace></mspace><mi>t</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>75</mn></mrow></math></span>, and <span><math><mrow><mn>3</mn><mo>.</mo><mn>8</mn><mo>±</mo><mn>0</mn><mo>.</mo><mn>28</mn></mrow","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102292"},"PeriodicalIF":1.9,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142006419","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
Asteroseismology of evolved stars in six star clusters observed by Kepler/K2 开普勒/K2观测到的六个星团中的演化恒星的小行星动力学
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-27 DOI: 10.1016/j.newast.2024.102290
Yun-A Jo, Heon-Young Chang
{"title":"Asteroseismology of evolved stars in six star clusters observed by Kepler/K2","authors":"Yun-A Jo,&nbsp;Heon-Young Chang","doi":"10.1016/j.newast.2024.102290","DOIUrl":"10.1016/j.newast.2024.102290","url":null,"abstract":"<div><p>In this study, we have explored the frequency separations, <span><math><mrow><mi>Δ</mi><mi>ν</mi></mrow></math></span> and <span><math><mrow><mi>δ</mi><msub><mrow><mi>ν</mi></mrow><mrow><mn>02</mn></mrow></msub></mrow></math></span>, the height and width of the oscillation power excess, <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>Gauss</mi></mrow></msub></math></span> and <span><math><mrow><mi>δ</mi><msub><mrow><mi>ν</mi></mrow><mrow><mi>env</mi></mrow></msub></mrow></math></span>, as a function of the frequency of maximum power <span><math><msub><mrow><mi>ν</mi></mrow><mrow><mi>max</mi></mrow></msub></math></span> by analyzing 187 evolved stars in six star clusters observed by the <em>Kepler</em>/<em>K2</em> missions. We have also examined the asteroseismic relation in the Christensen-Dalsgaard diagram. Given the importance of scaling relations, the dependency of asteroseismic scaling relations on physical quantities must be verified to reduce systematic errors through the exploration of observational data obtained from various sources. In this context, the star cluster provides a valuable means to assess the age and metallicity. Focusing on evolved stars with <span><math><mrow><mn>30</mn><mspace></mspace><mi>μ</mi><mi>Hz</mi><mo>&lt;</mo><msub><mrow><mi>ν</mi></mrow><mrow><mi>max</mi></mrow></msub><mo>&lt;</mo><mn>220</mn><mspace></mspace><mi>μ</mi><mi>Hz</mi></mrow></math></span>, we have exploited the mass effect without the need for deriving the individual stellar mass. We have found that the considered relations appear to be associated with the age of star clusters, thereby the mass of the stars in a given evolutionary status for star clusters with different ages. By separately considering red giant branch stars and red clump stars, we have found that red clump stars appear more sensitive to the cluster age compared with red giant branch stars. It has been suggested that conclusions regarding the dependency of metallicity should be drawn with due care as outcomes are subject to how to treat metallicity. Finally, we conclude by briefly pointing out implications of our findings on asteroseismic inferences.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102290"},"PeriodicalIF":1.9,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141849232","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
Further lunar occultations results from the Trebur Observatory, 2021–24 2021-24 年特雷伯天文台的进一步月掩结果
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-27 DOI: 10.1016/j.newast.2024.102289
J.M. Ohlert , A. Richichi
{"title":"Further lunar occultations results from the Trebur Observatory, 2021–24","authors":"J.M. Ohlert ,&nbsp;A. Richichi","doi":"10.1016/j.newast.2024.102289","DOIUrl":"10.1016/j.newast.2024.102289","url":null,"abstract":"<div><p>Following up on our initial paper (Richichi and Ohlert, 2021), we report here on 60 lunar occultation events recorded between February 2021 and March 2024 at the Michael Adrian Observatorium. An improved version of the detector was employed for the present work. The program aims mainly at the direct measurement of the angular diameter of late-type stars, and the discovery or confirmation of binary stars with small separations. Among the results, we present first time angular diameter determinations for the late-type M giants IRC +20184 and BL Tau and for the bright carbon star TU Gem. Our diameter result for RX Cnc is the first determination outside the near-IR range. We also discovered or detected directly for the first time companions around SAO 79580, BL Tau again, and SAO 78643. The lunar occultation technique at our facility is capable to reach sources as faint as <span><math><mo>≈</mo></math></span> 10<!--> <!-->V magnitude with an angular resolution at the milliarcsecond level.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102289"},"PeriodicalIF":1.9,"publicationDate":"2024-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1384107624001039/pdfft?md5=87c54c6a624308f0bc6941d3934cc2c9&pid=1-s2.0-S1384107624001039-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141845323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Wormholes in dwarf and spiral galactic halo regions 矮星系和螺旋星系晕区的虫洞
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-20 DOI: 10.1016/j.newast.2024.102288
Mehedi Kalam , Amir Ghari , Irina Radinschi , Hosein Haghi , Farook Rahaman , Tandrima Chowdhury
{"title":"Wormholes in dwarf and spiral galactic halo regions","authors":"Mehedi Kalam ,&nbsp;Amir Ghari ,&nbsp;Irina Radinschi ,&nbsp;Hosein Haghi ,&nbsp;Farook Rahaman ,&nbsp;Tandrima Chowdhury","doi":"10.1016/j.newast.2024.102288","DOIUrl":"10.1016/j.newast.2024.102288","url":null,"abstract":"<div><p>In this article, we study solutions which describe wormholes in the halos of dwarf and massive spiral galaxies with different morphologies, masses, sizes and gas fractions by taking observed flat rotation curves as input. We assume Singular Isothermal Sphere (SIS) dark matter density profile. This result confirms the possible existence of wormholes in both dwarf and massive spiral galaxies.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102288"},"PeriodicalIF":1.9,"publicationDate":"2024-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141852015","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
Definition of multispectral camera system parameters to model the asteroid 2001 SN263 确定多光谱摄像系统参数以模拟小行星 2001 Sn263
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-15 DOI: 10.1016/j.newast.2024.102287
Gabriela de Carvalho Assis Goulart , Thiago Statella , Rafael Sfair
{"title":"Definition of multispectral camera system parameters to model the asteroid 2001 SN263","authors":"Gabriela de Carvalho Assis Goulart ,&nbsp;Thiago Statella ,&nbsp;Rafael Sfair","doi":"10.1016/j.newast.2024.102287","DOIUrl":"10.1016/j.newast.2024.102287","url":null,"abstract":"<div><p>In 2012, Brazil began the studies to send its first deep space exploration mission, ASTER, which would be the first mission to orbit a triple asteroid system, 2001 SN263. We aim to contribute to the ASTER mission by defining the parameters of a multispectral camera system that will be used to study the asteroid system 2001 SN263, through software simulations that should help planning the data collection. We inserted the shape model of the objects in the software POV-Ray and modeled two cameras, a Wide Angle (WAC) and a Narrow Angle (NAC). We inserted the asteroid's parameters and simulated the satellite position. We created various scenes so we could obtain a good view of the asteroid. Alpha is entirely visible only in the WAC images, while the NAC is expected to reveal surface details. Beta seems relatively small in the WAC images, whereas we obtain a broad view from the NAC at 100 km distance. Gamma, smaller than Beta, should provide more detailed images through the NAC, whereas the WAC images should be able to show its inclined orbit around Alpha. To see Gamma behind Alpha in its revolution movement, we would have to elevate the camera's orbit. The method employed to simulate images generated by satellite cameras can be applied to other scenarios where the target requires imaging, extending beyond the field of planetary geology.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102287"},"PeriodicalIF":1.9,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141712259","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 compact stars with two fluids 用两种流体模拟紧凑恒星
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-11 DOI: 10.1016/j.newast.2024.102286
Pedro Mafa , Vishnu Kakkat , Amos Kubeka , Mantile Lekala
{"title":"Modeling compact stars with two fluids","authors":"Pedro Mafa ,&nbsp;Vishnu Kakkat ,&nbsp;Amos Kubeka ,&nbsp;Mantile Lekala","doi":"10.1016/j.newast.2024.102286","DOIUrl":"10.1016/j.newast.2024.102286","url":null,"abstract":"<div><p>In this paper, we study the curved Krori–Barua spacetime geometry to describe compact stars with two components: dark and ordinary matter, using a two-fluid model approach. We choose the equation of state derived from the rotational curves of galaxies for dark matter and the polytropic equation of state for ordinary matter. The physical requirements for a realistic compact star are satisfied using specific parameters. For the polytropic index <span><math><mrow><mi>η</mi><mo>=</mo><mn>2</mn></mrow></math></span>, we find the values of observed masses, reported in our previous investigation (Mafa et al., 2020).</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102286"},"PeriodicalIF":1.9,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1384107624001003/pdfft?md5=051c3f9eade0b3342ac0112088c30b75&pid=1-s2.0-S1384107624001003-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141637662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The role of radial viscosity force and anisotropic thermal conduction in hot accretion flow 热吸积流中径向粘滞力和各向异性热传导的作用
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-11 DOI: 10.1016/j.newast.2024.102276
Maryam Ghasemnezhad , Mohsen Khosravi
{"title":"The role of radial viscosity force and anisotropic thermal conduction in hot accretion flow","authors":"Maryam Ghasemnezhad ,&nbsp;Mohsen Khosravi","doi":"10.1016/j.newast.2024.102276","DOIUrl":"10.1016/j.newast.2024.102276","url":null,"abstract":"<div><p>Recent observational evidence confirms the weak-collision dynamics of hot optically thin accretion flows around Sgr A<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> and other nearby galactic nuclei. As a result, thermal conduction as a diffusion process can transfer the heat by electrons in a collisionless magnetized plasma. While most of the previous analytical studies consider the azimuthal viscosity, the recent studies indicated that the radial viscosity strongly affects the properties of the advection dominated accretion discs. So, in this paper, we explore the roles of two parts of anisotropic thermal conduction (parallel and perpendicular) and radial viscosity in the hot accretion disc by considering axisymmetric and steady state assumptions in the presence of outflows that can transport energy from accretion disc outward. We use the set of self-similar solutions to solve the basic equations in our present model. Our solutions reveal that transverse thermal conduction as a cooling mechanism, leads to reductions in gas temperature, disc thickness, and accretion velocity of the disc, whereas the disc rotates at a fast rate. Moreover Our solutions indicate that the perpendicular thermal conduction and the radial viscosity have opposite behavior in the physical variables of the disc. Also, our results have indicated that the anisotropic thermal conduction is significant in the parameter space of radial viscosity, outflow in the regions that the physical constraints <span><math><mrow><msub><mrow><mi>t</mi></mrow><mrow><mi>i</mi><mi>n</mi></mrow></msub><mo>≥</mo><msub><mrow><mi>t</mi></mrow><mrow><mo>⊥</mo><mo>,</mo><mi>c</mi><mi>o</mi><mi>n</mi></mrow></msub></mrow></math></span> and <span><math><mrow><msub><mrow><mi>q</mi></mrow><mrow><mo>∥</mo><mo>,</mo><mi>c</mi><mi>o</mi><mi>n</mi></mrow></msub><mo>⩽</mo><msub><mrow><mi>q</mi></mrow><mrow><mo>⊥</mo><mo>,</mo><mi>c</mi><mi>o</mi><mi>n</mi></mrow></msub></mrow></math></span> are satisfied.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102276"},"PeriodicalIF":1.9,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141696176","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
Spectral evolution and photo-ionization analysis of Nova Cas 2020 (V1391 Cas) Cas 2020 新星(V1391 Cas)的光谱演变和光电离分析
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-06 DOI: 10.1016/j.newast.2024.102273
G.M. Hamed , H.H. Esenoglu , A.I. Galeev
{"title":"Spectral evolution and photo-ionization analysis of Nova Cas 2020 (V1391 Cas)","authors":"G.M. Hamed ,&nbsp;H.H. Esenoglu ,&nbsp;A.I. Galeev","doi":"10.1016/j.newast.2024.102273","DOIUrl":"https://doi.org/10.1016/j.newast.2024.102273","url":null,"abstract":"<div><p>We present spectroscopic observations of Nova Cas 2020 <strong>(V1391 Cas)</strong> obtained using the Russian Turkish Telescope during different stages of its 2020 outburst. We followed the spectral evolution of the nova until it entered the nebular phase. The expansion velocity of the ejecta reached <span><math><mrow><mo>∼</mo><mn>780</mn><mspace></mspace><msup><mrow><mi>km s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. The fluxes of the neutral [O I] lines at wavelengths 6300, 6364, and 5577 <span><math><mtext>̊A</mtext></math></span> were used to calculate the electron temperature and the mass of neutral oxygen in the ejecta. We found average values <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>e</mi></mrow></msub><mo>=</mo><mi>4890</mi><mspace></mspace><mi>K</mi></mrow></math></span>, <span><math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mi>OI</mi></mrow></msub><mo>=</mo><mi>2.54</mi><mo>×</mo><msup><mrow><mi>10</mi></mrow><mrow><mi>−5</mi></mrow></msup><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></mrow></math></span> which are consistent with the values calculated for other novae. We modeled the nova’s ejected envelope 515 days after its discovery and found that the log elemental abundances by number relative to Hydrogen of the envelope are He = −0.7, C = −5.5, O = −2.5, N = −2.0 and Ne = −4.0.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102273"},"PeriodicalIF":1.9,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141605542","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
LRS Bianchi type-I with Hubble’s horizon as IR cut-off in f(R) gravity 公式省略]引力中以哈勃视界为红外截止点的 LRS 比安奇 I 型
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-04 DOI: 10.1016/j.newast.2024.102274
Syed Mudassir Syed Iqbal , G.U. Khapekar , S.H. Shekh , A. Dixit
{"title":"LRS Bianchi type-I with Hubble’s horizon as IR cut-off in f(R) gravity","authors":"Syed Mudassir Syed Iqbal ,&nbsp;G.U. Khapekar ,&nbsp;S.H. Shekh ,&nbsp;A. Dixit","doi":"10.1016/j.newast.2024.102274","DOIUrl":"10.1016/j.newast.2024.102274","url":null,"abstract":"<div><p>we explored the holographic dark energy model using Hubble’s Horizon as the infrared (IR) cut-off in Locally Rotationally Symmetric (LRS) Bianchi type-I, considering the <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>R</mi><mo>)</mo></mrow></mrow></math></span> gravity framework in our analysis. In order to solve the field equations, we assume a relation <span><math><mrow><mi>F</mi><mo>∝</mo><mspace></mspace><msup><mrow><mi>a</mi></mrow><mrow><mi>m</mi></mrow></msup></mrow></math></span> and volumetric power law expansion (where <span><math><mi>m</mi></math></span> is constant). we have expressed various crucial cosmological parameters in terms of the redshift <span><math><mi>z</mi></math></span> and depicted them graphically to enhance our understanding of the expansion and evolution of the universe like holographic dark energy density (<span><math><msub><mrow><mi>ρ</mi></mrow><mrow><mi>Λ</mi></mrow></msub></math></span>), holographic dark energy pressure (<span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>Λ</mi></mrow></msub></math></span>), equation of state parameter (<span><math><mi>ω</mi></math></span>) , total energy density parameter (<span><math><mi>Ω</mi></math></span>) etc. Also, we analyzed the stability of the universe in our model through the squared speed of sound test and its validity by energy conditions. Ultimately, our model indicates that the universe is currently in an expanding phase, exhibiting an accelerating phase, closely approaching a flat geometry, and its behavior resembles that of a quintessence dark energy model.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102274"},"PeriodicalIF":1.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587749","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
New results on the two-body decay of neutrons shed new light on neutron stars 关于中子双体衰变的新成果为中子星带来新启示
IF 1.9 4区 物理与天体物理
New Astronomy Pub Date : 2024-07-02 DOI: 10.1016/j.newast.2024.102275
Eugene Oks
{"title":"New results on the two-body decay of neutrons shed new light on neutron stars","authors":"Eugene Oks","doi":"10.1016/j.newast.2024.102275","DOIUrl":"10.1016/j.newast.2024.102275","url":null,"abstract":"<div><p>In attempts to resolve the neutron lifetime puzzle, there was suggested a hypothetical decay of neutrons into some <em>unspecified</em> dark matter (DM) particles. Later there were performed studies on how the hypothetical decay of neutrons would affect neutron stars. Recently it was shown that with the allowance for the second solution of Dirac equation for hydrogen atoms, the theoretical branching ratio (BR) for the two-body decay of neutrons (compared to their three-body decay) is amplified by a factor of 3300 from 0.000004. So, the BR becomes about 1.3% in the excellent agreement with the “experimental” BR = (1.15 ± 0.27)% required for reconciling the two distinct experimental values of the neutron lifetime: one from the beam experiments, another from the trap experiments. This meant that the two-body decay of neutrons in the beam experiments (that count only the protons) plays a much more sizable part in the overestimation of the lifetime of neutrons in these experiments than previously thought. Hydrogen atoms corresponding to the second solution of Dirac equations are called the second flavor of hydrogen atoms (SFHA) by the analogy with the flavors of quarks. The existence of the SFHA is evidenced by four different types of atomic/molecular experiments. The primary feature of the SFHA is that due to having only the s-states, they do not emit or absorb the electromagnetic radiation (except for the 21 cm line): they are practically <em>dark</em>. The SFHA became a candidate for a part of DM for the first time after the SFHA-based successful qualitative and quantitative explanation of the perplexing observation by Bowman et al. of the anomalous absorption in the redshifted 21 cm line from the early Universe. In the present paper we analyzed how this neutron decay into the SFHA affects neutron stars. We showed that old neutron stars could very slowly generate the new <em>specific, described in detail</em> baryonic DM in the form of the SFHA. Some old neutron stars would release it into their tiny atmospheres, while some other old neutron stars would release it into the interstellar medium. Besides, mergers of a neutron star with another neutron star or with a black hole, accompanied by the ejection of neutron-rich material, can also lead to the formation of SFHA as the ejecta cools down. This is another interesting aspect of the multi-messenger astronomy focused on studying these mergers through the gravitational waves they generate. These mechanisms of generating new baryonic DM in the universe should have the fundamental importance. We point out the indirect observational evidence of the continuing generation of new baryonic DM. We hope that our results will stimulate a further research in this direction.</p></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"113 ","pages":"Article 102275"},"PeriodicalIF":1.9,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587750","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}
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