New Astronomy最新文献

Matter power spectrum in a power-law f(G) gravity

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-05-12 DOI: 10.1016/j.newast.2025.102423

Albert Munyeshyaka , Praveen Kumar Dhankar , Joseph Ntahompagaze

{"title":"Matter power spectrum in a power-law f(G) gravity","authors":"Albert Munyeshyaka , Praveen Kumar Dhankar , Joseph Ntahompagaze","doi":"10.1016/j.newast.2025.102423","DOIUrl":"10.1016/j.newast.2025.102423","url":null,"abstract":"<div><div>Cosmological models based on <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> gravity are efficient in fitting different observational datasets at both background and perturbation levels. This motivates the current study to take into account dynamical system analysis to investigate the matter power spectrum within the framework of modified Gauss–Bonnet gravity. After defining the dimensionless dynamical system variables for a power-law <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> model, We derive the full system of equations governing the energy density perturbations for both matter and Gauss–Bonnet fluids using the <span><math><mrow><mn>1</mn><mo>+</mo><mn>3</mn></mrow></math></span> covariant formalism. After solving the energy density perturbation equations, we compute the matter power spectrum. The importance of studying first order perturbations for the defined <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> model and the relevance of different initial conditions in computing the matter power spectrum are also stressed. It is reported that matter power spectrum for <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> gravity, for a particular functional form of <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mi>G</mi><mo>)</mo></mrow></mrow></math></span> model considered is not scale invariant as the case for General Relativity.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"120 ","pages":"Article 102423"},"PeriodicalIF":1.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143941885","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

Lightcurves of stars in the Chamaeleon I association 变色龙I星协中恒星的光曲线

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-05-10 DOI: 10.1016/j.newast.2025.102409

K. Neumannová , L. Kueß , E. Paunzen , K. Bernhard

引用次数: 0

Universal relationships for neutron stars from perturbative approach 从摄动方法看中子星的普遍关系

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-05-09 DOI: 10.1016/j.newast.2025.102422

Debasis Atta , Vinay Singh , D.N. Basu

{"title":"Universal relationships for neutron stars from perturbative approach","authors":"Debasis Atta , Vinay Singh , D.N. Basu","doi":"10.1016/j.newast.2025.102422","DOIUrl":"10.1016/j.newast.2025.102422","url":null,"abstract":"<div><div>The universal relationships for compact stars have been investigated employing perturbative approach using canonical (APR) and Brussels–Montreal Skyrme (BSk22, BSk24, BSk26) equations of state describing hadronic matter of neutron stars. The neutron star matter has been considered to be <span><math><mi>β</mi></math></span>-equilibrated neutron–proton–electron–muon matter at the core with a rigid crust. The multipole moments of a slowly rotating neutron star characterize its external gravitational field. These variables are dependent on the interior structure of the neutron star described by the equation of state of the neutron star matter. The properties of neutron stars, such as the mass, the radius, the dimensionless moment of inertia, the compactness, the Love number, the dimensionless tidal deformability and the dimensionless quadrupole moment have been calculated and relations among these quantities have been explored. It is found that most of these relations do not depend sensitively on the details of the internal structure of neutron stars. Such universality implies that the measurement of a single quantity appearing in a universal relation would automatically provide information about the others, notwithstanding the fact that those may not be accessible observationally. Such relations can be utilized to assess the deformability of compact stars by measuring their moment of inertia, to evaluate spin in binary inspirals by resolving degeneracies in gravitational wave detection or to examine General Relativity in a manner that is not reliant on nuclear structure.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"120 ","pages":"Article 102422"},"PeriodicalIF":1.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143936934","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

Diagnozing star formation in the Chamaeleon–Musca dark cloud complex 在变色龙-穆斯卡黑云复合体中诊断恒星形成

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-05-05 DOI: 10.1016/j.newast.2025.102421

H.Y. Chen , W.P. Chen

{"title":"Diagnozing star formation in the Chamaeleon–Musca dark cloud complex","authors":"H.Y. Chen , W.P. Chen","doi":"10.1016/j.newast.2025.102421","DOIUrl":"10.1016/j.newast.2025.102421","url":null,"abstract":"<div><div>We present a comprehensive young stellar census of the Chamaeleon–Musca dark-cloud complex. Searching in a <span><math><mrow><mn>12</mn><mo>°</mo><mo>×</mo><mn>12</mn><mo>°</mo></mrow></math></span> sky area using Gaia DR3 data for astrometric membership, aided by 2MASS and ALLWISE infrared colors for disk-bearing objects, we have found not only members known to be associated with main clouds, but also inter-cloud candidates discovered for the first time. We confirm that Cha I is active in starbirth with more than 200 members. Cha II harbors some 50 members, among which three are projected in northern Cha III, which itself lacks any star-forming activity. The subcluster Cha I South is at an average distance of <span><math><mo>∼</mo></math></span>189 pc, slightly nearer than Cha I North at <span><math><mo>∼</mo></math></span>192 pc, whereas Cha II is farther at <span><math><mo>∼</mo></math></span>198 pc, forming a distance sequence. The isochrone fitting indicates a consistent age of about 3 Myr for Cha I and Cha II, suggesting coeval star formation. Our work confirms the Musca filament with the paucity of fully grown young stars. Serendipitously, in the foreground (<span><math><mo>∼</mo></math></span>110 pc), some members of <span><math><mi>ϵ</mi></math></span> Cha or LCC associations are projected in our studied field; they are more evolved pre-main sequence objects or dwarfs with an age spread of 5-20 Myr. Also detected in our data is a part of the cluster UPK569 older (<span><math><mo>∼</mo></math></span>30 My) and farther (<span><math><mo>∼</mo></math></span>250 pc) than Chamaeleon clouds. An analysis of two separate clouds some 10 deg to the south-east, Cha-East I and Cha-East II, uncovers no young stars, lending support that Cha I and Cha II mark the end of the sequence of the latest episode of triggered star formation by the Sco-Cen OB association.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"120 ","pages":"Article 102421"},"PeriodicalIF":1.9,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143923423","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

An MHD simulation of the possible modulations of stellar CMEs radio observations by an exoplanetary magnetosphere 通过系外行星磁层对恒星cme射电观测可能调制的MHD模拟

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-29 DOI: 10.1016/j.newast.2025.102420

Soumitra Hazra , Ofer Cohen , Igor V. Sokolov

{"title":"An MHD simulation of the possible modulations of stellar CMEs radio observations by an exoplanetary magnetosphere","authors":"Soumitra Hazra , Ofer Cohen , Igor V. Sokolov","doi":"10.1016/j.newast.2025.102420","DOIUrl":"10.1016/j.newast.2025.102420","url":null,"abstract":"<div><div>Type II radio bursts are the indicator of adverse space weather in a stellar system. These radio bursts are the consequence of shock wave acceleration due to the coronal mass ejection (CME). In this study, we conduct a series of magnetohydrodynamic (MHD) simulations of CME-driven star–planet systems to investigate how close-in exoplanets modulate radio burst characteristics. We use a model for the stellar wind with a close-in exoplanet, and a CME model based on the eruption of a flux rope. We are able to generate synthetic radio burst images from our MHD simulations. We find that radio burst like phenomena is most likely to be observed for moderately active solar like stars and close-in exoplanetary systems have significant influence on the nature of radio burst spectrum. We find that when the exoplanet’s magnetic field is relatively weak, its magnetosphere compresses the CME plasma, increasing local density and shifting the radio emission to higher frequencies. Conversely, a strong planetary magnetic field results in a large magnetosphere that prevents effective CME-shock development, producing weaker radio emission concentrated at lower frequencies, particularly at the flanks of the CME. For highly active solar-like stars, strong overlying stellar magnetic fields suppress the CME shock, greatly diminishing radio burst visibility. For HD 189733 (moderate stellar field), only intensity difference is visible when the CME arrives the planet. We also do not find significant modulation in the radio emission by a close-in exoplanet system when the stellar magnetic field is complex. In summary, our findings highlight that the nature of the radio burst spectrum is strongly dependent on both the topology of the stellar magnetic field and the magnetic strength of close-in exoplanets.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"119 ","pages":"Article 102420"},"PeriodicalIF":1.9,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143891931","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

Optical spectroscopy and photoionization modeling of four selected planetary nebulae 四个选定的行星状星云的光谱学和光电离模型

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-28 DOI: 10.1016/j.newast.2025.102413

Şengül Yalgın , Nazım Aksaker , Nurullah Erzincan , Aysun Akyuz

{"title":"Optical spectroscopy and photoionization modeling of four selected planetary nebulae","authors":"Şengül Yalgın , Nazım Aksaker , Nurullah Erzincan , Aysun Akyuz","doi":"10.1016/j.newast.2025.102413","DOIUrl":"10.1016/j.newast.2025.102413","url":null,"abstract":"<div><div>We present the results of chemical abundance measurements for four compact planetary nebulae (PNe) located in the Northern Hemisphere, selected from the HASH (Hong Kong/Australian Astronomical Observatory/Strasbourg H-alpha Planetary Nebula) database. Spectral data were collected using the medium-resolution TUG Faint Object Spectrograph and Camera mounted on the 1.5 m RTT telescope at the TÜBİTAK National Observatory. For each object, we determined key physical parameters, including the extinction coefficient, electron density, electron temperature, and ionization correction factors. Additionally, we constructed the spectral energy distribution across multiple wavelengths for each PN using advanced photoionization modeling with the <span>cloudy</span> code. The elemental abundance analysis, focusing on He, N, O, Ne, S, Cl, and Ar, indicates that the chemical composition of these PNe is consistent with both solar and Galactic values. The central stars exhibit effective temperatures ranging from approximately 53,000 to 180,000 K and luminosities between 2,500 and 9,000 L<span><math><msub><mrow></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>. Based on their positions on the H-R diagram and post-AGB evolutionary tracks, their initial masses are estimated to range from 1 to 3 M<span><math><msub><mrow></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>, with nebular masses between 0.69 and 2.34 M<span><math><msub><mrow></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>. The ages of the nebulae, calculated to be between <span><math><mo>∼</mo></math></span>300 and 5,000 years, align with previous findings, emphasizing their evolutionary importance.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"119 ","pages":"Article 102413"},"PeriodicalIF":1.9,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143887318","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

Resonant absorption of kink MHD waves in twisted flux tubes with thick transitional layer 具有厚过渡层的扭转磁通管中扭结MHD波的共振吸收

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-25 DOI: 10.1016/j.newast.2025.102419

Karam Bahari

{"title":"Resonant absorption of kink MHD waves in twisted flux tubes with thick transitional layer","authors":"Karam Bahari","doi":"10.1016/j.newast.2025.102419","DOIUrl":"10.1016/j.newast.2025.102419","url":null,"abstract":"<div><div>The effect of magnetic twist on the resonant absorption of propagating magnetohydrodynamic (MHD) waves in coronal flux tubes with thick transitional layer has been investigated. The flux tube is assumed to be a density enhancement in a zero beta plasma with twisted magnetic field. In the thin tube approximation a perturbation method is used to solve equations of motion analytically in all the regions of the tube including the transitional layer. The dispersion relation is solved numerically to investigate both the temporal and spatial damping of the kink MHD waves. We have introduced a symmetry of the MHD waves in the presence of magnetic twist which has not been discussed earlier, this symmetry allows us to study only forward waves. The efficiency of resonant absorption depends on the sign of the twist parameter. For negative values of the twist parameter resonant absorption becomes sufficiently effective, and for positive values of the twist parameter, especially for a thick transitional layer, resonant absorption becomes almost ineffective. For a specific twist parameter, resonant absorption is efficient for the waves in which the sign of their wave number is opposite to that of the twist parameter.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"119 ","pages":"Article 102419"},"PeriodicalIF":1.9,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143891933","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

The first photometric and dynamical study of the eclipsing binary star V951 Perseus 首次对食双星英仙座V951的光度和动力学研究

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-24 DOI: 10.1016/j.newast.2025.102418

Bin Zhang , Wei Tao , Zhen Zhong

{"title":"The first photometric and dynamical study of the eclipsing binary star V951 Perseus","authors":"Bin Zhang , Wei Tao , Zhen Zhong","doi":"10.1016/j.newast.2025.102418","DOIUrl":"10.1016/j.newast.2025.102418","url":null,"abstract":"<div><div>In this paper, we studied the short-period eclipsing binary V951 Perseus (hereafter V951 Per) using the newly observed four-color (<span><math><mi>B</mi></math></span>, <span><math><mi>V</mi></math></span>, <span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>, <span><math><msub><mrow><mi>I</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span>) light curves and the TESS data. Photometric solutions suggest that it is a W-subtype shallow contact binary with a mass ratio of <span><math><mi>q</mi></math></span> = 1.95 and a contact degree of <span><math><mi>f</mi></math></span> = 7.0%. In order to fit the asymmetrical light curves well, a cool star-spot on the less massive component is employed. Based on our new CCD eclipsing times and the data published until now, changes in the eclipsing times were analyzed using the <span><math><mrow><mi>O</mi><mo>−</mo><mi>C</mi></mrow></math></span> method. The <span><math><mrow><mi>O</mi><mo>−</mo><mi>C</mi></mrow></math></span> diagram indicates that the orbital period of V951 Per is decreasing at a rate of <span><math><mrow><mi>d</mi><mi>P</mi><mo>/</mo><mi>d</mi><mi>t</mi></mrow></math></span> = −8.79 × 10<sup>−8</sup> d yr<sup>−1</sup>, superposed on a cyclic oscillation with an amplitude of 0.0046 d and a period of 11.4 yr. The secular period decrease can be explained by the mass transfer from the more massive component to the less massive one or by the angular momentum loss. The cyclic oscillation may be interpreted as the light-travel-time effect because of the presence of an unseen third body. We calculated the mass of the third companion as <span><math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mn>3</mn></mrow></msub><mi>s</mi><mi>i</mi><mi>n</mi><mrow><mo>(</mo><mi>i</mi><mo>)</mo></mrow></mrow></math></span> = 0.18 <span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"119 ","pages":"Article 102418"},"PeriodicalIF":1.9,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876580","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

Multi-point Hermite methods for the N-body problem n体问题的多点Hermite法

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-24 DOI: 10.1016/j.newast.2025.102415

Alexander J. Dittmann

{"title":"Multi-point Hermite methods for the N-body problem","authors":"Alexander J. Dittmann","doi":"10.1016/j.newast.2025.102415","DOIUrl":"10.1016/j.newast.2025.102415","url":null,"abstract":"<div><div>Numerical integration methods are central to the study of self-gravitating systems, especially those comprised of many bodies or otherwise beyond the reach of analytical methods. Predictor–corrector schemes, both multi-step methods and those based on 2-point Hermite interpolation, have found great success in the simulation of star clusters and other collisional systems. Higher-order methods, such as those based on Gaussian quadratures and Richardson extrapolation, have also proven popular for high-accuracy integrations of few-body systems, particularly those that may undergo close encounters. This work presents a family of high-order schemes based on multi-point Hermite interpolation. When applied as multi-step multi-derivative schemes, these can be seen as generalizing both Adams–Bashforth–Moulton methods and 2-point Hermite methods; I present results for the 6th-, 9th-, and 12th-order 3-point schemes applied in this manner using variable timesteps. In a star cluster-like test problem, the 3-point 6th-order predictor–corrector scheme matches or outperforms the standard 2-point 4th-order Hermite scheme at negligible <span><math><mrow><mi>O</mi><mrow><mo>(</mo><mi>N</mi><mo>)</mo></mrow></mrow></math></span> additional cost, potentially reducing the necessary number of force evaluations in simulations of large-<span><math><mi>N</mi></math></span> collisional systems by factors of <span><math><mrow><mo>∼</mo><mn>3</mn></mrow></math></span> or more. I also present a number of high-order time-symmetric schemes up to 18th order, which have the potential to improve the accuracy and efficiency of long-duration simulations.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"119 ","pages":"Article 102415"},"PeriodicalIF":1.9,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143891932","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 catalog of low frequency quasi-periodic oscillations from cygnus X-2 天鹅座X-2低频准周期振荡的目录

IF 1.9 4区物理与天体物理

New Astronomy Pub Date : 2025-04-23 DOI: 10.1016/j.newast.2025.102417

Kavitha Arur , Divyesh Ved

引用次数: 0