Pub Date : 2025-05-12DOI: 10.1016/j.newast.2025.102423
Albert Munyeshyaka , Praveen Kumar Dhankar , Joseph Ntahompagaze
Cosmological models based on 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 model, We derive the full system of equations governing the energy density perturbations for both matter and Gauss–Bonnet fluids using the 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 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 gravity, for a particular functional form of model considered is not scale invariant as the case for General Relativity.
{"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}
Pub Date : 2025-05-10DOI: 10.1016/j.newast.2025.102409
K. Neumannová , L. Kueß , E. Paunzen , K. Bernhard
Star-forming regions are essential for studying very young stellar objects of various masses. They still contain a significant amount of dust and gas. We present a study of light curves of stars in the field of the Chamaeleon I association. We use automatic spectral classification with MKCLASS to identify the spectral types of the stars in the field with a light curve from the NEOWISE and Gaia surveys. The light curves are analysed using the software Peranso and astropy. We also used VSX to identify the variability type. Based on astrometry, we have identified 92 stars, 73 of which are members of the association. We received light curves for 55 stars from the Gaia survey and for 69 stars from the ALLWISE/NEOWISE survey. For 28 of them, it was possible to determine the types of variables, mostly T Tauri and Orion variables. The spectral types of the members are mostly cooler M-type stars, with one being a possible chemically peculiar (CP) star. The non-members associated with light curve measurements include spectral types A-G with one CP candidate.
{"title":"Lightcurves of stars in the Chamaeleon I association","authors":"K. Neumannová , L. Kueß , E. Paunzen , K. Bernhard","doi":"10.1016/j.newast.2025.102409","DOIUrl":"10.1016/j.newast.2025.102409","url":null,"abstract":"<div><div>Star-forming regions are essential for studying very young stellar objects of various masses. They still contain a significant amount of dust and gas. We present a study of light curves of stars in the field of the Chamaeleon I association. We use automatic spectral classification with MKCLASS to identify the spectral types of the stars in the field with a light curve from the NEOWISE and Gaia surveys. The light curves are analysed using the software Peranso and astropy. We also used VSX to identify the variability type. Based on astrometry, we have identified 92 stars, 73 of which are members of the association. We received light curves for 55 stars from the Gaia survey and for 69 stars from the ALLWISE/NEOWISE survey. For 28 of them, it was possible to determine the types of variables, mostly T Tauri and Orion variables. The spectral types of the members are mostly cooler M-type stars, with one being a possible chemically peculiar (CP) star. The non-members associated with light curve measurements include spectral types A-G with one CP candidate.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"120 ","pages":"Article 102409"},"PeriodicalIF":1.9,"publicationDate":"2025-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143948099","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}
Pub Date : 2025-05-09DOI: 10.1016/j.newast.2025.102422
Debasis Atta , Vinay Singh , D.N. Basu
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 -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.
利用正则态方程（APR）和描述中子星强子物质的brussel - montreal Skyrme （BSk22, BSk24, BSk26）状态方程，采用微扰方法研究了致密星的普适关系。中子星物质被认为是具有刚性外壳的β-平衡中子-质子-电子-介子物质。缓慢旋转的中子星的多极矩是其外部引力场的特征。这些变量取决于中子星物质状态方程所描述的中子星内部结构。计算了中子星的质量、半径、无因次转动惯量、紧致度、Love数、无因次潮汐变形量和无因次四极矩等性质，并探讨了这些性质之间的关系。我们发现，这些关系中的大多数并不敏感地依赖于中子星内部结构的细节。这种普遍性意味着，对普遍关系中出现的单个量的测量将自动提供关于其他量的信息，尽管这些量可能无法通过观测获得。这种关系可以用来通过测量它们的转动惯量来评估致密恒星的可变形性，通过解决引力波探测中的简并来评估双星的自旋，或者以一种不依赖于核结构的方式来检验广义相对论。
{"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}
Pub Date : 2025-05-05DOI: 10.1016/j.newast.2025.102421
H.Y. Chen , W.P. Chen
We present a comprehensive young stellar census of the Chamaeleon–Musca dark-cloud complex. Searching in a 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 189 pc, slightly nearer than Cha I North at 192 pc, whereas Cha II is farther at 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 (110 pc), some members of 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 UPK 569 older (30 My) and farther (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.
我们提出了一个全面的变色龙-穆斯卡黑云复合体的年轻恒星普查。利用盖亚DR3数据在12°×12°的天空区域搜索天体测量成员，借助2MASS和ALLWISE红外颜色对盘状天体进行辅助，我们不仅发现了已知的与主云相关的成员，还发现了首次发现的云间候选成员。我们确认Cha I在starbirth活跃，有200多名会员。Cha II拥有大约50个成员星，其中3个位于Cha III的北部，本身没有任何恒星形成活动。亚星团Cha I South的平均距离为~ 189 pc，比Cha I North （~ 192 pc）稍近，而Cha II则更远，为~ 198 pc，形成了一个距离序列。等时线拟合表明Cha I和Cha II的年龄一致，约为3myr，表明恒星形成于同一时期。我们的工作证实了Musca灯丝中缺乏成熟的年轻恒星。偶然地，在前景（~ 110 pc）中，一些λ Cha或LCC关联的成员被投影到我们的研究领域；它们是更进化的前主序层天体或矮星，年龄分布在5- 20myr。在我们的数据中还发现了UPK 569星团的一部分，它比变色龙云更古老（~ 30my），距离更远（~ 250pc）。对东南方向约10度的两个独立星云——Cha- east I和Cha- east II的分析发现，没有发现年轻的恒星，这支持了Cha I和Cha II标志着scoc - cen OB协会最新触发恒星形成序列的结束。
{"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 UPK<!--> <!-->569 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}
The diversity of type Ia supernovae (SNe Ia) has become increasingly apparent with the rapid growth in observational data. Understanding the explosion mechanism of SNe Ia is crucial for their cosmological calibration and for advancing our knowledge of stellar physics. The estimation of 56Ni mass produced in these events is key to elucidating their explosion mechanism. This study compares two methods of 56Ni mass estimation. We first examine the relationship between peak luminosity and the second maximum in near-infrared (NIR) bands using observations of 18 nearby SNe Ia. Based on this relationship, we estimate the Ni mass for a set of nine well-observed SNe Ia using the Arnett rule. Additionally, we estimate the 56Ni mass using bolometric light curves of these SNe through energy conservation arguments. A comparison of these two estimation methods using Student’s t-test reveals no statistically significant differences between the estimates. This finding suggests that both methods provide robust estimates of Ni mass in SNe Ia.
{"title":"How accurate are current 56Ni mass estimates in Type Ia Supernovae?","authors":"Jagriti Gaba , Rahul Kumar Thakur , Naresh Sharma , Dinkar Verma , Shashikant Gupta","doi":"10.1016/j.newast.2025.102411","DOIUrl":"10.1016/j.newast.2025.102411","url":null,"abstract":"<div><div>The diversity of type Ia supernovae (SNe Ia) has become increasingly apparent with the rapid growth in observational data. Understanding the explosion mechanism of SNe Ia is crucial for their cosmological calibration and for advancing our knowledge of stellar physics. The estimation of <sup>56</sup>Ni mass produced in these events is key to elucidating their explosion mechanism. This study compares two methods of <sup>56</sup>Ni mass estimation. We first examine the relationship between peak luminosity and the second maximum in near-infrared (NIR) bands using observations of 18 nearby SNe Ia. Based on this relationship, we estimate the Ni mass for a set of nine well-observed SNe Ia using the Arnett rule. Additionally, we estimate the <sup>56</sup>Ni mass using bolometric light curves of these SNe through energy conservation arguments. A comparison of these two estimation methods using Student’s t-test reveals no statistically significant differences between the estimates. This finding suggests that both methods provide robust estimates of Ni mass in SNe Ia.</div></div>","PeriodicalId":54727,"journal":{"name":"New Astronomy","volume":"120 ","pages":"Article 102411"},"PeriodicalIF":1.9,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144167722","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}
Pub Date : 2025-04-29DOI: 10.1016/j.newast.2025.102420
Soumitra Hazra , Ofer Cohen , Igor V. Sokolov
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.
{"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}
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 cloudy 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. 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, with nebular masses between 0.69 and 2.34 M. The ages of the nebulae, calculated to be between 300 and 5,000 years, align with previous findings, emphasizing their evolutionary importance.
我们展示了从HASH（香港/澳大利亚天文台/斯特拉斯堡h - α行星状星云）数据库中选择的北半球四个致密行星状星云（PNe）的化学丰度测量结果。光谱数据的收集使用中分辨率的TUG暗天体光谱仪和安装在TÜBİTAK国家天文台1.5 m RTT望远镜上的相机。对于每个物体，我们确定了关键的物理参数，包括消光系数、电子密度、电子温度和电离校正因子。此外，我们利用先进的光电离建模和cloudy代码构建了每个PN跨多个波长的光谱能量分布。元素丰度分析，重点是He， N， O, Ne， S， Cl和Ar，表明这些PNe的化学组成与太阳和银河系的值一致。中心恒星的有效温度大约在53,000到180,000 K之间，光度在2,500到9,000 L⊙之间。根据它们在H-R图上的位置和agb后的演化轨迹，它们的初始质量估计在1到3 M⊙之间，星云质量在0.69到2.34 M⊙之间。该星云的年龄在300年到5000年之间，与之前的发现一致，强调了它们在进化中的重要性。
{"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}
Pub Date : 2025-04-25DOI: 10.1016/j.newast.2025.102419
Karam Bahari
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.
{"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}
Pub Date : 2025-04-24DOI: 10.1016/j.newast.2025.102418
Bin Zhang , Wei Tao , Zhen Zhong
In this paper, we studied the short-period eclipsing binary V951 Perseus (hereafter V951 Per) using the newly observed four-color (, , , ) light curves and the TESS data. Photometric solutions suggest that it is a W-subtype shallow contact binary with a mass ratio of = 1.95 and a contact degree of = 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 method. The diagram indicates that the orbital period of V951 Per is decreasing at a rate of = −8.79 × 10−8 d yr−1, 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 = 0.18 .
{"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}
Pub Date : 2025-04-24DOI: 10.1016/j.newast.2025.102415
Alexander J. Dittmann
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 additional cost, potentially reducing the necessary number of force evaluations in simulations of large- collisional systems by factors of 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.
{"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}
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