Astrophysics and Space Science最新文献

{"title":"Characteristics of solar flares associated with ground level enhancement events","authors":"YunFeng Zhang,&nbsp;Kazi A. Firoz","doi":"10.1007/s10509-025-04438-3","DOIUrl":"10.1007/s10509-025-04438-3","url":null,"abstract":"<div><p>We conduct a statistical analysis on 76 ground level enhancement (GLE) events to examine the characteristics of their associated solar flares. Our analysis reveals that GLE-associated flares predominantly occur within the longitude range of 20^∘–100^∘ west and belong to higher optical and soft X-ray flare classes, with 84% being X-class. The average flare longitudes for GLEs with increase rates above 100% and 10% are found to be 53.67^∘ ± 15.31^∘ and −59.18^∘ ± 8.04^∘, respectively, with a concentration near 55^∘ west longitude for high-intensity GLEs. Statistical timing analysis shows that 69% of GLE events commence after the associated flare peaks, with an average delay of 17.18 ± 7.06 minutes. These findings underscore the impact of solar flare location and intensity on GLE production and highlight the role of interplanetary magnetic field structures in guiding energetic particle transport toward Earth. The results further suggest that both flare-driven and CME-driven acceleration mechanisms play a role in GLE initiation, with particle transport conditions influencing the observed timing relationships.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144140173","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 long-term optical flux variations of Compact Symmetric Objects","authors":"Subhashree Swain,&nbsp;Vaidehi S. Paliya,&nbsp;D. J. Saikia,&nbsp;C. S. Stalin,&nbsp;Arya Venugopal,&nbsp;A. K. Bhavya,&nbsp;C. D. Ravikumar","doi":"10.1007/s10509-025-04436-5","DOIUrl":"10.1007/s10509-025-04436-5","url":null,"abstract":"<div><p>Compact Symmetric Objects (CSOs) are a distinct category of jetted active galactic nuclei (AGN) whose optical variability characteristics have not been well investigated. We present here the results of our investigation on the optical flux and colour variability properties of a bona fide sample of 38 CSOs. We used the <span>(g)</span>-, <span>(r)</span>- and <span>(i)</span>-bands data from the Zwicky Transient Facility survey that spans a duration of about 5 years. We also considered a comparison sub-sample of blazars that includes 5 flat spectrum radio quasars and 12 BL Lac objects with redshifts and <span>(g)</span>-band magnitudes similar to the limited sub-sample of 9 CSOs. These two sub-samples of AGN, chosen for this comparative study of their long-term optical variability, represent different orientations of their relativistic jets with respect to the observer. We found that both CSOs and blazars exhibit optical flux variations, although variability of CSOs is lower than that of blazars. The observed variability in both CSOs and blazars is attributed to the relativistic jets and the increased optical variations in blazars relative to CSOs are likely due to beaming effects. CSOs and blazars exhibit similar colour variations, with both of them showing a bluer when brighter trend. Such a colour variability pattern is expected due to processes associated with their relativistic jets.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144090968","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":"Extended analysis on stability, capture, and escape for planar retrograde periodic orbit around Earth","authors":"Kenta Oshima","doi":"10.1007/s10509-025-04434-7","DOIUrl":"10.1007/s10509-025-04434-7","url":null,"abstract":"<div><p>Cislunar space has been attracting interest as a strategic place to connect Earth and interplanetary space. This paper extends our previous analysis on the use of retrograde periodic orbits around Earth for staging orbits. The orbit of interest is found to be linearly stable against the luni-solar gravitational perturbation, yet its Moon-grazing geometry leads to modest <span>(Delta v)</span> to capture into (escape from) the orbit via lunar flyby. In the analysis of capture trajectories, we globally search for transfer trajectories from the vicinity of Earth. It is found that Sun-perturbed, multi-revolutional transfer is a promising option to reduce the launch energy and insertion <span>(Delta v)</span>. In the escape analysis, transfer from the periodic orbit toward interplanetary space via powered Earth flyby is studied. Temporal insertion into an unstable periodic orbit that is in a retrograde <span>(1:1)</span> mean-motion resonance is found to be a favorable option to flexibly tune the escape direction.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144074000","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":"Retrograde co-orbital motion with Jupiter. Periodic orbits and dynamical maps","authors":"George Voyatzis,&nbsp;Thomas Kotoulas,&nbsp;Maria Helena Moreira Morais","doi":"10.1007/s10509-025-04439-2","DOIUrl":"10.1007/s10509-025-04439-2","url":null,"abstract":"<div><p>This study aims to provide comprehensive insights into the dynamics of retrograde co-orbital motion, contributing to our understanding of the origin and evolution of retrograde asteroids in the solar system. The paper studies retrograde co-orbital motion with Jupiter through the computation of symmetric periodic orbits in both planar and spatial circular restricted three-body problems. The research begins with an analysis of families of the planar circular problem at which there exist three main families of co-orbital motion. Starting from the vertical critical orbits of these families we extend our study to three-dimensional configurations, revealing that most spatial families exhibit instability. The phase-space structure is also explored by using dynamical stability maps under various initial conditions. These maps help identify regions of stable motion within predominantly chaotic domains. The theoretical framework is applied to asteroid (514107) Ka’epaoka’awela, demonstrating its chaotic nature with a Lyapunov time of approximately 6350 years, despite remaining in co-orbital resonance with Jupiter for many million years.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10509-025-04439-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944351","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":"Impact of a variable cosmological constant on stellar matter configurations in Finch-Skea spacetime","authors":"M. Ilyas,&nbsp; Maha,&nbsp;Salma Nawaz,&nbsp;Falak Sher,&nbsp;Fawad Khan","doi":"10.1007/s10509-025-04435-6","DOIUrl":"10.1007/s10509-025-04435-6","url":null,"abstract":"<div><p>In this study, a variable cosmological constant model is created for anisotropic star structures, which satisfies the remaining physical requirements, and validates the required energy conditions (Ecs), and TOV equations. First, the Finch-Skea spacetime solution is taken into account as a static spherically symmetric metric. Moreover, external Schwarzschild geometry is taken into account to correlate our internal stellar structure and determine the values of the constants used in the Finch-Skea spacetime solution. Finally, in this paper, multiple aspects are discussed, such as the radius, compactness, stresses, stability, density profile, and masses under the variable cosmological constant model in <span>(f(R,T))</span> gravity for various stars.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944332","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":"Performance evaluation of AfriTEC model during quiet and disturbed time over East African sector","authors":"Efrem Amanuel Data,&nbsp;Dejene Ambisa Terefe,&nbsp;Gebre Kalute Gebino","doi":"10.1007/s10509-025-04437-4","DOIUrl":"10.1007/s10509-025-04437-4","url":null,"abstract":"<div><p>This study evaluates the performance of the African Regional Ionospheric Total Electron Content (AfriTEC) model across varying solar activity levels in the East African sector. Focusing on the solar maximum year of 2014 and the solar minimum year of 2009, the analysis utilizes TEC data derived from GPS receivers at six IGS stations. The study compares the AfriTEC model outputs with the corresponding GPS-TEC data, demonstrating a consistency between the datasets. The diurnal variation pattern of model shows an underestimation at daytime than nighttime can be visible at all days. Observed vertical TEC shows best performance at morning and afternoon, the ionosphere is most stable and poor at evening and pre-down. The seasonal variation shows that with maximum values at March equinox and December solstice months and minimum during June solstice and September equinox months. The model best during equinoxes compared to solstices more uniform ionization and stable ionospheric condition. The monthly variation of model accuracy show that during the solar maximum year, the model exhibited poor performance, with a peak error of 14 recorded in DODM during disturbed times and a minimum error of 2 in ADIS during the same conditions. In contrast, during the solar minimum year, the model’s accuracy improved significantly, showing a minimum error of 1 at MOIU during quiet times and a maximum error of 5.5 at MBAR during disturbed times. We emphasize that the decision from this paper would complement in the model performance at various geophysical conditions over the equatorial and low latitude sector like East African region.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944352","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 multifield emulator","authors":"Sambatra Andrianomena,&nbsp;Sultan Hassan,&nbsp;Francisco Villaescusa-Navarro","doi":"10.1007/s10509-025-04440-9","DOIUrl":"10.1007/s10509-025-04440-9","url":null,"abstract":"<div><p>We present the application of deep networks to learn the distribution of multiple large-scale fields, conditioned exclusively on cosmology while marginalizing over astrophysics. Our approach develops a generalized multifield emulator based purely on theoretical predictions from the state-of-the-art hydrodynamic simulations of the CAMELS project, without incorporating instrumental effects which limit the analysis to specifics of a particular large-scale survey design. To this end, we train a generative adversarial network to generate images composed of three different channels that represent gas density (Mgas), neutral hydrogen density (HI), and magnetic field amplitudes (B). We consider an unconstrained model and another scenario where the model is conditioned on the matter density <span>(Omega _{mathrm{m}})</span> and the amplitude of density fluctuations <span>(sigma _{8})</span>. We find that the generated images exhibit great quality which is on a par with that of data, visually. Quantitatively, we find that our model generates maps whose statistical properties, quantified by probability distribution function (PDF) of pixel values and auto-power spectra, agree reasonably well up to the second moment with those of the real maps. The relative deviation between the PDFs is about 25<span>(%)</span> in both moments with larger deviations at the tails. The error between the two auto-power spectra is approximately less than 20<span>(%)</span> on scales larger than <span>(k = 10 h/)</span>Mpc, but becomes larger on smaller scales. Moreover, the mean and standard deviation of the cross-correlations between fields in all maps produced by the emulator are in good agreement with those of the real images, which indicates that our model generates instances whose maps in all three channels describe the same physical region. Furthermore, a CNN regressor, which has been trained to extract <span>(Omega _{mathrm{m}})</span> and <span>(sigma _{8})</span> from CAMELS multifield dataset, recovers the cosmology from the maps generated by our conditional model, achieving coefficient of determination values <span>(R^{2} = 0.96)</span> and 0.83 corresponding to <span>(Omega _{mathrm{m}})</span> and <span>(sigma _{8})</span> respectively. This further demonstrates the great capability of the model to mimic CAMELS data. Our model can be useful for generating data, 1000 multiple images in ∼3 seconds as opposed to a simulation which takes days for one realization, that are required to analyze the information from upcoming multi-wavelength cosmological surveys.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143944173","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":"Performance evaluation of low-cost GNSS receivers for extracting ionospheric TEC","authors":"Jufeng Yang,&nbsp;Shuhui Li,&nbsp;Aochuan Zhang,&nbsp;Shaoqiu Chen,&nbsp;Han Wang","doi":"10.1007/s10509-025-04432-9","DOIUrl":"10.1007/s10509-025-04432-9","url":null,"abstract":"<div><p>This paper aims to compare the performance of the low-cost Global Navigation Satellite System (GNSS) receiver u-blox ZED-F9P and the geodetic receiver JAVAD SIGMA G3T on vertical total electron content (VTEC) estimation, and to evaluate the impacts of different antennas on VTEC estimation. Using the undifferenced and uncombined Precise Point Positioning (PPP) algorithm to process GNSS data on April 15, September 11, and September 12, 2021. Then we compared the accuracy of VTEC and differential code bias (DCB) estimation between the low-cost GNSS receiver and the geodetic receiver. The results showed that VTEC extracted from low-cost GNSS receiver and geodetic receiver are consistent with the Global Ionospheric Model (GIM) products. However, the low-cost GNSS receiver’s VTEC accuracy is slightly lower, with the residual root mean square (RMS) values ranging from 1.07 to 1.72 TECU (Total Electron Content Unit) and the absolute mean bias ranging from −1.48 to −0.85 TECU. Additionally, satellite DCBs from the geodetic receiver were closer to CAS products than those from the low-cost GNSS receiver, with more satellites exhibiting absolute bias less than 1 nanosecond. Moreover, we analyzed the impact of different antennas (SEPCHOKE_B3E6 and JAVAD GrAnt-G3T) on VTEC estimation. For two receivers, VTEC differences between antennas are less than 1 TECU, with RMS of the biases between different antennas less than 0.35 TECU and mean biases do not exceed 0.21 TECU.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143938641","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":"Exploring the formation mechanisms of double neutron star systems: an analytical perspective","authors":"Ali Taani,&nbsp;Mohammed Abu-Saleem,&nbsp;Mohammad Mardini,&nbsp;Hussam Aljboor,&nbsp;Mohammad Tayem","doi":"10.1007/s10509-025-04433-8","DOIUrl":"10.1007/s10509-025-04433-8","url":null,"abstract":"<div><p>Double Neutron Stars (DNSs) are unique probes to study various aspects of modern astrophysics. Recent discoveries have confirmed direct connections between DNSs and supernova explosions. This provides valuable information about the evolutionary history of these systems, especially regarding whether the second-born Neutron Star (NS) originated from either a Core-Collapse (<span>(CC)</span>) or Electron-Capture Supernovae (<span>(ECSNe)</span>) event. The provided scale diagram illustrates the distribution of different types of DNSs on the basis of their orbital parameters and other factors, including mass loss. As a result, the physical processes in DNSs vary depending on the formation mechanisms of the second-born NS and characteristics of the systems. <span>(ECSNe)</span> processes are typically associated with merging systems (<span>(etimes {P_{orb}}&lt; 0.05)</span>), while <span>(CC)</span> processes are more commonly linked to non-merging systems (<span>(etimes {P_{orb}}&gt; 0.05)</span>). Our results suggest a critical mass threshold of 1.30<span>(M_{odot } pm 0.22M_{odot } )</span> (critical value) for the <span>(ECSNe)</span> process to form an NS, while <span>(CC)</span> processes might occur at higher masses. Examining the orbital parameters of DNSs in a known gravitational potential can enhance our understanding of the theoretical predictions for DNS progenitor characteristics. It turns out that the <span>(ECSNe)</span> process predominantly produces DNS systems with short orbital (<span>(P_{orb} leq 0.25 d)</span>), nearly circular orbits (<span>(esimeq 0.2)</span>), accompanied by minimal kick velocities imparted on the proto-NS and significant mass loss. In contrast, their orbital dynamics in a known gravitational potential plays a crucial role in enhancing our understanding of the SNe geometry and the formation and evolution processes among different NS samples.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143919269","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":"Dark energy dynamics in teleparallel gravity with hyperbolic scale factor","authors":"A. O. Dhore,&nbsp;M. R. Ugale","doi":"10.1007/s10509-025-04431-w","DOIUrl":"10.1007/s10509-025-04431-w","url":null,"abstract":"<div><p>This paper uses the Friedmann–Robertson–Walker (FRW) line element to simulate the development of the universe and explores the cosmological implications of Tsallis Holographic Dark Energy (THDE) in the modified <span>(f(T))</span> teleparallel gravity framework. Teleparallel gravity, in which torsion substitutes curvature as the geometric structure of spacetime, describes the accelerated expansion of the universe in the absence of exotic matter. The work examines key cosmological parameters, such as the Hubble parameter, equation of state (EOS), deceleration parameter, jerk parameter, and <span>(Om)</span> diagnostics, under both interacting and non-interacting conditions by integrating the THDE model, derived from non-additive Tsallis entropy, with <span>(f(T))</span> gravity. To provide a smooth transition from deceleration to acceleration, the study uses a hyperbolic scale factor, <span>(a(t) = left [sinh (alpha t)right ]^{frac{1}{beta }})</span>. It explains how THDE fits into the model of the dynamics of the universe, with a focus on stability analysis using square sound speed and scalar field correspondence. We show that while the non-interacting THDE model remains stable (with <span>(v_{s}^{2}&gt;0)</span>), the interacting model can develop instabilities for larger coupling values. Our analysis, calibrated against 57 Hubble data points, yields best-fit parameters <span>(alpha = {-59.416}_{-0.625}^{+0.625})</span> and <span>(beta = {-1.303}_{-0.022}^{+0.022})</span>, with an <span>(R^{2})</span> value of 0.9321 and a best-fit <span>(H_{0})</span> of 67.8 km/s/Mpc. The study also examines energy conditions, highlighting the role of interaction terms in the development of dark energy (DE) and matter components. Graphical and numerical investigations demonstrate the capacity of the model to reflect empirical data, providing a complete framework for understanding the interactions of DE and teleparallel gravity. This methodology expands the theoretical framework for examining the accelerating expansion of the universe and offers alternate viewpoints on the DE paradigm.</p></div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143908750","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}