Astrophysics and Space Science最新文献

{"title":"Numerical and statistical insights into (f(R,T)) cosmology: GRP, RK4, and MLE approaches","authors":"Navya Jain,&nbsp;R. K. Mishra","doi":"10.1007/s10509-025-04480-1","DOIUrl":"10.1007/s10509-025-04480-1","url":null,"abstract":"<div><p>This study explores the stability of an <span>(f(R,T))</span> gravity-based cosmological model using perturbation techniques and numerical methods. Stability conditions are examined by analyzing the growth rate of small perturbations in density and pressure. Furthermore, the Runge-Kutta fourth-order (RK4) method is employed to numerically track the evolution of these perturbations and validate the theoretical predictions. To ensure consistency with observational data, the model is tested against Hubble parameter measurements and the Pantheon Type Ia supernova dataset using the Maximum Likelihood Estimation (MLE) method. The findings provide deeper insights into the stability of modified gravity models and underscore the significance of combining analytical, numerical, and observational approaches in cosmological studies.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144914785","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}

{"title":"Anisotropic compact stars on generalized Tolman-Kuchowicz spacetime with quadratic equation of state","authors":"Hemani R. Acharya,&nbsp;Dishant M. Pandya,&nbsp;Bharatkumar B. Parekh,&nbsp;V. O. Thomas","doi":"10.1007/s10509-025-04478-9","DOIUrl":"10.1007/s10509-025-04478-9","url":null,"abstract":"<div><p>This paper presents the class of solutions to the Einstein field equations for the uncharged static spherically symmetric compact object PSR J0952–0607 by using Generalized Tolman - Kuchowicz space-time metric with quadratic equation of state. We have obtained the bound on the model parameter n graphically and achieved the stable stellar structure of the mathematical model of a compact object. The stability of the generated model is examined by the Tolman - Oppenheimer - Volkoff equation and the Harrison-Zeldovich-Novikov criterion. This anisotropic compact star model fulfills all the required stability criteria including the causality condition, adiabatic index, Buchdahl condition, Herrera’s cracking condition, and pertains free from central singularities.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144897207","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}

{"title":"On ultra-long period (53.8 min) pulsar ASKAP J1935+2148: coherent radio emission triggered by local superstrong magnetic reconnection","authors":"Zhi-Yao Yang,&nbsp;Cheng-Min Zhang,&nbsp;De-Hua Wang,&nbsp;Erbil Gügercinoğlu,&nbsp;Xiang-Han Cui,&nbsp;Jian-Wei Zhang,&nbsp;Shu Ma,&nbsp;Yun-Gang Zhou","doi":"10.1007/s10509-025-04479-8","DOIUrl":"10.1007/s10509-025-04479-8","url":null,"abstract":"<div><p>The eight ultra-long period pulsars (ULPPs) in radio bands have been discovered recently, e.g., ASKAP J1935+2148 with a spin period of 53.8 min, which are much longer than those of normal pulsars, spanning from 0.016 s to 23.5 s, however the origins, spin evolutions and emission mechanisms of these sources are still puzzling. We investigate how the ultra-long period of ASKAP J1935+2148 is evolved by the braking of relativistic particle wind, in a time scale of about 0.1 - 1 Myr, from a normal pulsar with local superstrong magnetic fields. In addition, it is noticed that the ULPPs in the period versus period derivative diagram are much below the “death line”, implying their different characteristics from the normal pulsars. Five sources (including ASKAP J1935+2148) in total eight ULPPs share the rotational energy loss rates to be lower than their respective radio emission luminosities, a phenomenon that can be accounted for by the sustainable radio bursts induced through the reconnection of locally concentrated magnetic field lines. The diversity and complexity of ULPP radio emissions should be closely related to the presence of magnetic reconnection rather than rotational powered discharges in the gaps. Furthermore, it is suggested that the coherent radio emissions of pulsars may have two origins, one from the rotation-powered electric voltage that accounts for the normal pulsar phenomena and the other from the magnetic reconnection-induced continual radio bursts that account for the ULPP observations.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144880740","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}

{"title":"Forbush decreases during strong geomagnetic storms: time delays, rigidity effects, and ICME-driven modulation","authors":"O. Ahmed,&nbsp;B. Badruddin,&nbsp;M. Derouich","doi":"10.1007/s10509-025-04477-w","DOIUrl":"10.1007/s10509-025-04477-w","url":null,"abstract":"<div><p>We present the relationship between Forbush decreases (FDs) and associated geomagnetic storms, as well as their connections to interplanetary (IP) solar wind parameters, using high resolution minute data. FDs were classified into groups based on main phase decrease steps, and each group was analyzed using superposed epoch analysis. The results reveal that fast, turbulent, high-field sheath structures form before and pass during the onset of coronal mass ejection (CME) driven FDs, whereas corotating interaction region (CIR) driven events exhibit delayed amplification and more perturbed dynamics. Time lags between the onset of FDs and geomagnetic storms were calculated and discussed, providing insights crucial for space weather forecasting. Correlation analyses between FD amplitude and peak values of various IP parameters were performed and discussed. The relationship between FDs and geomagnetic storms was analyzed, revealing that for CME-driven events, FD amplitudes exhibit a stronger correlation with moderate and strong geomagnetic storms compared to extreme storms. The weaker correlation during extreme CME-driven storms may result from complex magnetospheric responses caused by successive events and prolonged southward interplanetary magnetic field Bz, unlike the more direct responses observed in moderate and strong single-event storms. Interplanetary coronal mass ejection (ICME) manifestations were also correlated with FD amplitude, showing that events with fast forward shocks and compression sheath regions exhibit stronger correlations than those without shocks. Furthermore, we analyzed the energy dependence of FD amplitude using data from twelve neutron monitor stations at different latitudes and altitudes across the globe. As a result, the cosmic ray (CR) energy spectrum exhibits a two-step linear dependence with the FD amplitude, in the lower rigidity FD amplitude decreases sharply, while in higher rigidity regimes, the decrease is more gradual. A broader energy spectrum is recommended for more comprehensive conclusions.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144868781","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}

{"title":"Early galaxies and supermassive black holes discovered by the James Webb Space Telescope","authors":"Yuichi Harikane","doi":"10.1007/s10509-025-04467-y","DOIUrl":"10.1007/s10509-025-04467-y","url":null,"abstract":"<div><p>Observations by the James Webb Space Telescope (JWST) have led to a series of groundbreaking discoveries that challenge our current understanding of early galaxy formation. A large number of galaxies have been surprisingly identified during the epoch of cosmic dawn, the redshift of <span>(zsim 11-14)</span>, 13.4 to 13.5 billion years ago, far exceeding theoretical predictions. Additionally, many faint AGNs hosting supermassive black holes have been discovered at <span>(z&gt;4)</span>. What was happening in the early universe? This article provides an overview of these latest findings.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10509-025-04467-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144868931","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}

{"title":"The “second stellar spectrum:” rotating hot massive star linear spectropolarimetry with the Öhman effect","authors":"J. Patrick Harrington,&nbsp;Richard Ignace,&nbsp;Kenneth G. Gayley,&nbsp;Jeremy J. Drake","doi":"10.1007/s10509-025-04475-y","DOIUrl":"10.1007/s10509-025-04475-y","url":null,"abstract":"<div><p>To understand better the polarized radiative transfer near the surface of rotating massive stars that remain nearly spherically symmetric, we use plane-parallel stellar atmosphere models to explore the unique opportunity presented by the Öhman effect. This effect refers to the predicted variation in linear polarization across a rotationally broadened absorption line, due to the interaction of that line with the spatially varying continuum polarization across the face of a strongly scattering photosphere, such as found in hot stars. Even if the rotation is weak enough for the star to remain spherically symmetric, the Öhman effect persists because differential absorption induced by the rotational Doppler shift of the line breaks the symmetry that would otherwise cancel the continuum polarization in the absence of that line. Neglecting rotational distortion effects, the net polarization across the line vanishes, yet resolved line profiles display a telltale triple-peak polarization pattern, with one strong polarization peak at line center and two smaller ones in the line wings at a position angle that is rotated 90 degrees from the line center. The far ultraviolet (FUV) is emphasized because both the polarization amplitude and the specific luminosity are greatest there for photospheres with effective temperatures between about 15,000 and 20,000 K. Additionally, larger polarizations result for lower-gravity atmospheres. There is a high density of spectral lines in the FUV, leading to a rich “second stellar spectrum” in linear polarization (analogous to the “second solar spectrum”) that is made observable with stellar rotation. Some hot stars exhibit extreme rotation, which suppresses the polarimetric amplitude for the forest of weaker FUV lines, but a few strong lines such as the Si<span>iv</span> 140 nm doublet still give observable polarizations at high rotation speeds even before rotational distortion effects of the atmosphere are considered. Thus polarizations at the level of 0.1% to 1% are achievable across individual lines for a wide variety of B-type stars. We highlight the prospects for accessing the unique information encoded in the Öhman effect with future moderate-resolution spaceborne spectropolarimetric missions in the FUV.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144861556","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}

{"title":"Mission analysis for the HENON CubeSat mission to a large Sun-Earth distant retrograde orbit","authors":"Stefano Cicalò,&nbsp;Elisa Maria Alessi,&nbsp;Lorenzo Provinciali,&nbsp;Paride Amabili,&nbsp;Giorgio Saita,&nbsp;Davide Calcagno,&nbsp;Maria Federica Marcucci,&nbsp;Monica Laurenza,&nbsp;Gaetano Zimbardo,&nbsp;Simone Landi,&nbsp;Roger Walker,&nbsp;Michael Khan","doi":"10.1007/s10509-025-04473-0","DOIUrl":"10.1007/s10509-025-04473-0","url":null,"abstract":"<div><p>The HEliospheric pioNeer for sOlar and interplanetary threats defeNce (HENON) mission is a CubeSat Space Weather mission, designed to operate in a Sun-Earth Distant Retrograde Orbit (DRO) at more than 10 million km from the Earth. HENON will embark payloads tailored for Space Weather (SWE) observations, i.e., a high-resolution energetic particle radiation monitor, a Faraday cup, and a magnetometer enabling it to provide quasi-real-time monitoring of the interplanetary conditions in deep space. HENON has many important goals, such as demonstrating CubeSat capabilities in deep space, including long-duration electric propulsion with periodic telemetry and command, and robust attitude control for deep-space operations. It will pave the way for a future fleet of spacecraft on DROs, providing continuous near real-time measurements for SWE forecasting. This paper focuses on the mission analysis performed for phase A/B, with the main goal of defining a baseline transfer trajectory to a heliocentric DRO in co-orbital motion with the Earth. The proposed transfer leverages a rideshare opportunity on a mission escaping Earth’s gravity field, most likely one headed toward the Sun–Earth L₂ region, and relies exclusively on on-board electric propulsion to reach deep space, making it a pioneering demonstration of this approach and the technology. Under appropriate assumptions on the electric propulsion system performances, s/c mass and propellant budget, it will be shown that the HENON target DRO can be reached in about 1 year, taking into account also periodic interruptions of thrusting to allow for Telemetry, Tracking and Command.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144832326","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}

{"title":"Gravitational wave distance estimation using intrinsic signal properties: dark sirens as distance indicators","authors":"Trisha V,&nbsp;Rakesh V,&nbsp;Arun Kenath","doi":"10.1007/s10509-025-04466-z","DOIUrl":"10.1007/s10509-025-04466-z","url":null,"abstract":"<div><p>Gravitational Waves (GWs) provide a powerful means for cosmological distance estimation, circumventing the systematic uncertainties associated with traditional electromagnetic (EM) indicators. This work presents a model for estimating distances to binary black hole (BBH) mergers using only GW data, independent of EM counterparts or galaxy catalogs. By utilizing the intrinsic properties of the GW signal, specifically the strain amplitude and merger frequency, our model offers a computationally efficient preliminary distance estimation approach that could complements existing Bayesian parameter estimation pipelines. In this work, we examine a simplified analytical expression for the GW luminosity distance derived from General Relativity (GR), based on the leading-order quadrupole approximation. Without incorporating post-Newtonian (PN) or numerical relativity (NR) corrections, or modeling spin, eccentricity, or inclination, we test how closely this expression can reproduce distances reported by full Bayesian inference pipelines. We apply our model to 87 events from the LIGO-Virgo-Kagra (LVK) Gravitational Wave Transient Catalogues (GWTC), computing distances for these sources. Our results demonstrate consistent agreement with GWTC-reported distances, further supported by graphical comparisons that highlight the model’s performance across multiple events.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144814380","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}

{"title":"The 3He((alpha ), (gamma ))7Be reaction in effective field theory","authors":"Hossein Sadeghi,&nbsp;Maryam Khoddam","doi":"10.1007/s10509-025-04476-x","DOIUrl":"10.1007/s10509-025-04476-x","url":null,"abstract":"<div><p>We present a theoretical analysis of the ³He(<span>(alpha )</span>, <span>(gamma )</span>)⁷Be radiative capture reaction, using pionless effective field theory (EFT) at the leading order. What sets our approach apart is the unique combination of direct capture mechanisms and resonant processes that involve the <span>(7/2^{-})</span> excited state of ⁷Be at 429 keV. By rigorously examining electromagnetic multipole transitions, we’ve managed to achieve a theoretical uncertainty of just 4.1% for the astrophysical S-factor. Our calculated value of <span>(S(0) = 0.511 pm 0.021text{ keV}cdot )</span>b aligns impressively with the recommended experimental value of <span>(0.529 pm 0.018text{ keV}cdot )</span>b. At the temperatures found in the solar core (<span>(T_{9} = 0.015)</span>), our reaction rate of <span>((9.2 pm 0.4) times 10^{3}text{ cm}^{3}text{ mol}^{-1}text{ s}^{-1})</span> helps to clear up some long-standing discrepancies in stellar models. Interestingly, our multipole decomposition shows a surprising persistence of M1 contributions (35.2% at resonance) that goes beyond what typical single-particle models would predict, underscoring the significance of two-body currents. The theoretical uncertainties we encountered are mainly due to EFT truncation errors (2.8%) and variations in low-energy constants (2.1%). These findings have direct implications for solar neutrino flux predictions and calculations of primordial lithium abundance.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144814381","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}

{"title":"Cosmological dynamics in modified theory of gravitation with a mixture of perfect fluid and dark energy","authors":"M. R. Ugale,&nbsp;A. O. Dhore","doi":"10.1007/s10509-025-04474-z","DOIUrl":"10.1007/s10509-025-04474-z","url":null,"abstract":"<div><p>This research investigates cosmic dynamics within the context of <span>(f(mathcal{R},mathcal{L}_{m}))</span> gravity, concentrating on a binary mixing of perfect fluid and dark energy in a Plane Symmetric space-time. By incorporating the non-linear form of <span>(f(mathcal{R},mathcal{L}_{m}))</span> as <span>(f(mathcal{R},mathcal{L}_{m})=frac{mathcal{R}}{2}+mathcal{L}_{m}^{alpha })</span>, it investigates late-time cosmic acceleration and the transition from matter-dominated to dark energy-dominated epochs. The analysis includes the quintessence and Chaplygin gas models, demonstrating their role in the dynamics of energy density, effective pressure, and anisotropy. The model is validated through parameterization using observational data, such as Hubble parameter datasets, which result in an excellent level of agreement with empirical findings. Advanced diagnostics, like the jerk, statefinder, and <span>(Om)</span> diagnostics, show that <span>(f(mathcal{R},mathcal{L}_{m}))</span> gravity is different from previous cosmological models. This lets us explain the expansion of the universe in terms of geometry. This study provides a strong basis for future research on modified gravity, anisotropic cosmological models, and the role of dark energy in the evolution of the universe.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144814541","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}