Journal of Astrophysics and Astronomy最新文献

{"title":"Composite anisotropic star model with a color-flavor-locked core","authors":"Amos V Mathias,&nbsp;Jason M Mkenyeleye","doi":"10.1007/s12036-026-10181-0","DOIUrl":"10.1007/s12036-026-10181-0","url":null,"abstract":"<div><p>We present a new non-singular exact model describing a composite compact stellar object with core–envelope structure generated from the Einstein field equations. The model represents a compact star whose core is composed of anisotropic strange quark matter consistent with CFL EoS, while the envelope consists of neutron fluid governed by a quadratic EoS in the absence of an electric field. The spacetime geometry is assumed to be static and spherically symmetric. The model closely describes the compact object GW200210. The hydrostatic equilibrium is analyzed using the Tolman–Oppenheimer–Volkoff (TOV) equation. The model produces stellar configurations with masses and radii comparable to those reported in earlier observations. In addition, the model satisfies various stability criteria and energy conditions. The behaviors of the metric potentials, matter variables, stability indicators, and energy conditions are all regular and physically acceptable throughout the stellar interior.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838348","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":"CCD (UBV(RI)_{KC}) photometry of the open cluster NGC 6793 and its dynamical evolution","authors":"ZAHRA Al,&nbsp;Yüksel Karataş,&nbsp;Raúl Michel,&nbsp;Charles Bonatto,&nbsp;Orhan Güneş,&nbsp;İnci Akkaya Oralhan,&nbsp;Eyüp Kaan Ülgen","doi":"10.1007/s12036-026-10168-x","DOIUrl":"10.1007/s12036-026-10168-x","url":null,"abstract":"<div><p>We present new astrophysical parameters for the open cluster NGC 6793 based on new CCD <span>(UBV(RI)_{KC})</span> photometry. We derived a reddening of <span>(E(B-V) = 0.24 pm 0.02)</span> mag and a heavy element abundance of <span>(Z = 0.024)</span> (<span>([Fe/H] = +0.20)</span> dex). Padova isochrone fitting to the <span>(V times (B-V))</span> colour-magnitude diagram yields an intermediate age of <span>(525 pm 51)</span> Myr and a distance modulus of <span>(mu = 8.80 pm 0.05)</span> mag, corresponding to a distance of <span>(d = 575 pm 58)</span> pc from the Sun. The core radius of NGC 6793 appears to be shrinking due to advanced dynamical evolution (<span>(log tau _{2} = 1.13)</span>), driven by mass segregation and the evaporation of low-mass stars from the central region. The ratios of core to half-mass radius (<span>(R_{c}/R_{h})</span>) and half-mass to Jacobi radius (<span>(R_{h}/R_{J})</span>) indicate that the cluster’s evolution is governed by the combined effects of internal two-body relaxation, mass segregation, and external tidal perturbations. The ratio <span>(R_{t}/R_{J} = 0.99)</span> suggests that the cluster is currently in a tidally filling state. The parameter pairs (<span>(t_{diss}/t_{rlx_{1}} = 40)</span>, <span>(log R_{J}/R_{c} = 0.72)</span>) and (<span>(R_{h}/R_{J} = 0.38)</span>, <span>(log rho _{amb} = -0.88)</span>) place NGC 6793 among the relatively compact clusters within <span>(R_{GC} &lt; 7.9)</span> kpc. This implies a compact internal structure that is stable against the combined effects of two-body encounters and tidal heating. Given its current state, NGC 6793 will likely dissolve and disperse before entering the final contraction phase (<span>(R_{4})</span> regime).</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783142","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":"Longitudinal development analysis of extensive air showers using CORSIKA simulations","authors":"Ali A. Shihab,&nbsp;A. A. Al-Rubaiee","doi":"10.1007/s12036-026-10153-4","DOIUrl":"10.1007/s12036-026-10153-4","url":null,"abstract":"<div><p>We present a comprehensive analysis of the longitudinal development of Extensive Air Showers (EAS) simulated with CORSIKA version 7.7500 for proton, helium, and iron primaries at energies of 10¹⁵, 10¹⁶, and 10¹⁷ eV across zenith angles of 0°, 30°, and 45°. For each combination of primary type, energy, and zenith angle, 50 independent showers were simulated, resulting in a total of 450 simulated showers. The Gaisser–Hillas function was fitted to extract the depth of shower maximum (X_max) and the number of particles at maximum (N_max). Our results confirm the expected logarithmic increase of X_max with energy (~100 g/cm² per decade), as well as systematically shallower X_max for heavier primaries (iron vs. proton: ΔX_max ≈ 160 g/cm² at 10¹⁷ eV). The simulations also reproduce the expected sec (θ) scaling behavior. Multi-component analysis reveals distinct evolutionary patterns for electromagnetic, muonic, and hadronic components. These findings provide benchmark-level simulations for cosmic-ray composition studies and validate the CORSIKA framework for multi-parameter analyses of air-shower development.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783143","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":"Physics-informed ensemble learning for exoplanet transit detection: Combining box least squares, attention-based CNNs, and gradient boosting","authors":"Richar Andre Vilca-Solorzano,&nbsp;Dina Maribel Yana-Yucra,&nbsp;Vladimiro Ibañez-Quispe,&nbsp;Fred Torres-Cruz","doi":"10.1007/s12036-026-10172-1","DOIUrl":"10.1007/s12036-026-10172-1","url":null,"abstract":"<div><p>Exoplanet detection from transit photometry faces challenges from false positives and weak signals. Traditional methods like Box Least Squares (BLS) offer interpretability but limited sensitivity, while deep learning approaches lack inherent interpretability without post-hoc attribution methods such as Gradient-weighted Class Activation Mapping (Grad-CAM). We present a hybrid, interpretable pipeline integrating BLS period detection, attention-based convolutional neural networks (CNNs), and gradient-boosted trees (XGBoost) with physics-informed features, combined via optimised ensemble weighting. Trained on real Kepler observations augmented with physically realistic synthetic transits, the ensemble achieves a Receiver Operating Characteristic Area Under the Curve (ROC-AUC) of 0.9948 on held-out test data, with 91.9% recall (true positive rate) at a 0.6% false positive rate. This exceeds prior methods while maintaining fast inference (under 0.1 s per target), enabling scalable deployment to TESS and PLATO missions. SHapley Additive exPlanations (SHAP) and Grad-CAM analyses confirm the model learns physically meaningful features (transit depth, duration, signal detection efficiency) rather than spurious correlations. All code, trained weights, and Docker environments are publicly released for full reproducibility.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783325","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":"A declining trend in sunspot group tilt angles over three and half solar cycles: 21–24","authors":"M Hegde,&nbsp;Belur Ravindra,&nbsp;K M Hiremath","doi":"10.1007/s12036-026-10156-1","DOIUrl":"10.1007/s12036-026-10156-1","url":null,"abstract":"<div><p>The tilt angle, defined as the angle between the line connecting the two polarities of a sunspot group and the solar equator, plays a critical role in linking the Sun’s global magnetic field and is a key parameter in dynamo models. This study examines the long-term characteristics of sunspot group tilt angles using data from the Debrecen Photoheliographic Database (DPD), covering three and a half solar cycles (1974-2013). Using tilt angles provided in the DPD catalog, we compute annual averages and apply weighted linear regression to assess long-term trends, along with wavelet transform analysis to identify short-term periodicities. Our analysis reveals a significant, consistent decrease in the magnitude of sunspot tilt angles, with an average yearly decline of approximately <span>(0.06 pm 0.01)</span> degrees. Additionally, a wavelet analysis indicates a short-term 4–6 year periodicity.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782782","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":"Impact of disk potential on motion around triangular points of the restricted five-body problem","authors":"Jagadish Singh,&nbsp;Achonu Joseph Omale","doi":"10.1007/s12036-026-10176-x","DOIUrl":"10.1007/s12036-026-10176-x","url":null,"abstract":"<div><p>The paper examines the impacts of disk potential on motion of a test particle around the triangular Lagrangian points (TLPs) of the restricted five body problem (R5BP). The setup is such that, the test particle moves under the gravitational attractions of four unequal massive bodies and the configuration is enclosed by a disk. The dynamical equations are deduced and the locations, zero velocity curves (ZVCs) and linear stability of the TLPs are explored numerically when the test particle gravitates in the vicinity of a stellar and planetary systems. Additionally, the impact of the mass parameter shows that the test particle is positioned nearest to the line joining the central star and the secondary body for low mass parameter but drifts away as the mass parameter increases, while the impact of the radii of the disks of both systems shows that for smaller radius of the disk, the locations drifts away more while they drift towards the line joining the central bodies when they are larger. In the case of the ZVCs, it is seen that the increasing mass parameter reduces the region where motion is allowed while the radius of the gas disk increases the region where motion is allowed. The vicinity of the central body is no-travel zone for the test particle for both systems while the second body is also forbidden for the test particle to access in the stellar system. The stability is investigated and the TLPs are all stable in the planetary environment while instability is possible is the stellar system. Finally, the orbital stability of the test particle around the TLPs and the bodies in the setup is investigated using the Poincaré surface of sections (PSS) and it is seen that quasi-periodic orbits around the third and fourth body exists for both systems and the orbits are stable or unstable depending on the mass parameter and the system in which the test particle gravitates. The radii of the disk show that larger radii result in orbital instability, while smaller radius of the disk improves orbital stability. This study will contribute to the sparse available knowledge in the R5BP.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782781","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":"Moderate nesting and cross-equatorial asymmetry of active regions in Solar Cycle 24","authors":"A A Norton,&nbsp;A Mendez,&nbsp;R Chen,&nbsp;M Dikpati,&nbsp;S Aswin Amirtha Raj","doi":"10.1007/s12036-026-10157-0","DOIUrl":"10.1007/s12036-026-10157-0","url":null,"abstract":"<div><p>Solar Cycle 24 data are used to determine how often the Sun emerges sunspots in ‘activity nests’, i.e., regions where sunspots and active regions (ARs) repeatedly emerge. We use the Solar Photospheric Ephemeral Active Region (SPEAR) catalog created from Helioseismic and Magnetic Imager (HMI) data as well as the HMI Carrington Rotation maps of radial magnetic field, <span>(B_r)</span>. The Sun shows moderate nesting behavior with 41% (48%) of AR magnetic flux found in Northern (Southern) hemispheric nests that are short-lived (average lifetimes <span>(sim )</span>3.3–4.0 months). Different rotation rates are used to search for nests that may not be evident ‘by eye’. The maximum number of nests are found with slightly prograde rotational velocities, with significant nest flux also found at synodic 451–452 nHz prograde and 409–411 nHz retrograde frequencies. Nest patterns show strong hemispheric asymmetry, indicating that the physical origin of nests identified herein must also be asymmetric or antisymmetric across the equator.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782778","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":"DHARA: Data handling and automated reduction pipeline for AIMPOL","authors":"Namita Uppal,&nbsp;Shashikiran Ganesh,&nbsp;Santosh Joshi,&nbsp;Dmitry Blinov,&nbsp;Konstantinos Tassis,&nbsp;Sadhana Singh","doi":"10.1007/s12036-026-10177-w","DOIUrl":"10.1007/s12036-026-10177-w","url":null,"abstract":"<div><p>We present an automated data-reduction and analysis pipeline for optical linear polarimetric data obtained from a dual-beam polarimeter. The pipeline is optimized for observations acquired with the ARIES Imaging POLarimeter mounted at the Cassegrain focus of the 1.04-m Sampurnanand Telescope at ARIES. It is implemented using interactive Python routines that process raw images to derive the Stokes parameters, from which the degree of polarization and polarization angle are computed along with their uncertainties. The pipeline framework is designed to handle the reduction of both single-source and crowded-field observations. The identification of extraordinary (e-ray) and ordinary (o-ray) image pairs is a crucial step and is performed using different strategies for single-source and crowded-field data, while subsequent stages, such as photometric and polarimetric analysis, follow a common procedure. We validate the pipeline using observations of polarized standard stars acquired over multiple epochs between 2017 to 2025, and compare the results with values reported in the literature. To demonstrate the applicability of the pipeline to crowded-field observations, we apply it to polarimetric data of the Alessi 1 open cluster and compare with previously published results derived using traditional reduction methods. In both cases, the polarization parameters derived using the pipeline agree with literature values within <span>(2sigma )</span> uncertainties. Although developed for AIMPOL, the pipeline is readily adaptable to any dual-channel imaging polarimeter in which the e-ray and o-ray images are recorded in a FITS image from a single CCD.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782780","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":"Spectrophotometric and dynamical parameters of the two close binary systems: HIP 51360 and HIP 53206","authors":"Suhail Masda,&nbsp;Mashhoor Al-Wardat,&nbsp;Ahmad Abushattal,&nbsp;Awni Kasawneh","doi":"10.1007/s12036-026-10174-z","DOIUrl":"10.1007/s12036-026-10174-z","url":null,"abstract":"<div><p>We present a combination of the spectrophotometric fundamental stellar parameters of the two close visual binary systems, HIP 51360 and HIP 53206, for the first time based on Gaia observations. We did this by means of Al-Wardat’s complex method for analyzing binary and multiple systems with the aid of Kurucz’s atmosphere models. The method combines the results from spectroscopic and photometric analyses with those from interferometry to construct the combined synthetic spectral energy distributions and to thoroughly determine those fundamental parameters for both systems. In synthetic spectrophotometric analysis, the stellar masses are estimated as <span>(mathcal {M}_{Sph}=)</span> <span>(2.7pm 0.2, mathcal {M}_odot )</span> with an age of 1.26 Gyr for HIP 51360, and <span>(mathcal {M}_{Sph}=2.1pm 0.2, mathcal {M}_odot )</span> with an age of 7.94 Gyr for HIP 53206 based on the synthetic tracks with a metallicity of 0.019. In the dynamical analysis, we present the orbital parameters of the systems depending on measurements of the speckle interferometry, which are combined with the results of the spectrophotometric analysis to result in the new dynamical parallaxes as <span>(pi _{dyn}=11.59pm 0.32)</span> mas for HIP 51360 and <span>(pi _{dyn}=24.40pm 0.72)</span> mas for HIP 53206.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782779","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 insights from generalized ghost dark energy in (f(mathcal {Q},mathcal {C})) gravity","authors":"M. Sharif,&nbsp;M. Zeeshan Gul,&nbsp;M. Hassan Shahid","doi":"10.1007/s12036-026-10171-2","DOIUrl":"10.1007/s12036-026-10171-2","url":null,"abstract":"<div><p>The main aim of this manuscript is to explore the generalized ghost dark energy in the context of <span>(f(mathcal {Q},mathcal {C}))</span> theory, where <span>(mathcal {Q})</span> is non-metricity scalar and <span>(mathcal {C})</span> represent boundary term. To achieve that aim, we take an isotropic and homogeneous with an ideal distribution of matter. Our analysis includes a case with interacting fluids, encompassing both dark matter and dark energy. Also, we rebuild a functional form of <span>(f(mathcal {Q},mathcal {C}))</span> to examine how this modified model impacts cosmic evolution. The behavior of several cosmic parameters is examined for different parametric values. The stability of the generalized ghost dark energy model is assessed using the squared sound speed method, which confirms the rapid cosmic expansion. Moreover, we employ diagnostic tools to evaluate different phases of universe’s evolution. Our results are consistent with the latest empirical data, suggesting that the <span>(f(mathcal {Q},mathcal {C}))</span> model provides an accurate description of both dark energy and the universe’s evolution. The cosmological parameters are constrained using observational data from cosmic chronometers.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751878","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}