Journal of Astrophysics and Astronomy最新文献

{"title":"Electromagnetic interactions in magnetized Reissner–Nordström black holes","authors":"Chiging Lasa Polo,&nbsp;Heisnam Shanjit Singh","doi":"10.1007/s12036-025-10116-1","DOIUrl":"10.1007/s12036-025-10116-1","url":null,"abstract":"<div><p>In this work, we examine the dynamic motion of a test particle possessing both electrical charge and magnetic dipole moment in the presence of a Reissner–Nordström (RN) black hole (BH) situated within an externally asymptotically uniform magnetic field. The interaction between the external magnetic field and the motion of the test particle near the black hole was primarily discussed through the Lorentz force. In our study, the peak value of the effective potential of the particles decreases with increasing magnetic coupling parameter, <span>(beta )</span>. Additionally, the effects of the magnetic coupling parameter and the cyclotron frequency <span>(omega _0)</span> on the specific energy and angular momentum of the test particles for stable circular orbits are analyzed. An increase in both <span>(beta )</span> and <span>(omega _0)</span> is found to cause a decrease in both the specific energy and angular momentum of the test particles. We also derive the expression of magnetic coupling parameters for the black hole, and the correspondence to the external magnetic field is analyzed. Our study also focuses on the center-of-mass energy, <span>(E_{cm})</span>, of colliding particles. An increase in the magnetic coupling parameter leads to a decrease in the center-of-mass energy extracted by the collision of two particles.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145675101","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":"Optimizing supernova classification with interpretable machine learning models","authors":"Anurag Garg","doi":"10.1007/s12036-025-10113-4","DOIUrl":"10.1007/s12036-025-10113-4","url":null,"abstract":"<div><p>Photometric classification of Type Ia supernovae (SNe Ia) is critical for cosmological studies but remains difficult due to class imbalance and observational noise. While deep learning models have been explored, they are often resource-intensive and lack interpretability. We present a computationally efficient and interpretable classification framework that maintains high performance on imbalanced datasets. We emphasize the use of PR-AUC and F1-score as more informative metrics than ROC-AUC in severely imbalanced settings. Using an XGBoost ensemble optimized via Bayesian hyperparameter tuning, we classified light curves from the Supernova Photometric Classification Challenge (SPCC), comprising 21,318 events with a 3.19 imbalance ratio (non-Ia to Ia). Our model achieved a PR-AUC of <span>(0.993^{+0.03}_{-0.02})</span>, an F1-score of <span>(0.923 pm 0.008)</span>, and a ROC-AUC of <span>(0.976 pm 0.004)</span>, matching or exceeding deep learning performance on precision-recall trade-offs, while using fewer resources. Despite slightly lower overall accuracy, our method balances false positives and false negatives, improving the efficiency of spectroscopic follow-up. We show that optimized ensemble models offer a reproducible and lightweight alternative to complex architectures, particularly for large-scale surveys, such as the Legacy Survey of Space and Time (LSST), where transparency and efficiency are essential.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612415","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":"Combining local and global magnetohydrodynamic simulation frameworks to understand the evolution of coronal mass ejections","authors":"TALWINDER SINGH,&nbsp;SAMRIDDHI SANKAR MAITY,&nbsp;PIYALI CHATTERJEE,&nbsp;NIKOLAI POGORELOV","doi":"10.1007/s12036-025-10114-3","DOIUrl":"10.1007/s12036-025-10114-3","url":null,"abstract":"<div><p>Coronal mass ejections (CMEs) are one of the primary sources of space weather disturbances and associated geomagnetic storms on Earth. Magnetohydrodynamic simulations of magnetic flux ropes are being actively investigated as a method for forecasting CME arrival times, the distributions of the solar wind plasma, and the magnetic field. To succeed, it is important to constrain the properties of such flux ropes using observations. Local simulations of the solar corona make it possible to model CME eruptions, provided that the observational data are sufficient to specify adequate boundary conditions at the solar surface. However, these simulations are limited to local, wedge-shaped domains of the solar corona because global modeling of such eruptions can be too computationally expensive. In this work, we demonstrate that it is possible to perform global simulations of flux ropes by extracting their properties obtained in the local domain and inserting them into a global model. We do that using local solutions in a wedge-shaped domain between <span>(R_odot le rle 6 R_odot )</span>, which are inserted into a fully-spherical global corona background between <span>(1.03 le rle 30)</span> <span>(R_odot )</span>. We also provide a detailed discussion of our simulation results, both in the local and global domains.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612416","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":"Spectral study of the X-ray sources in NGC 4472","authors":"Thokchom Sanatombi,&nbsp;A. Senorita Devi,&nbsp;Akram Chandrajit Singha,&nbsp;K. Yugindro Singh","doi":"10.1007/s12036-025-10111-6","DOIUrl":"10.1007/s12036-025-10111-6","url":null,"abstract":"<div><p>In this study, we investigated the spectral properties of the X-ray point sources in the giant elliptical galaxy NGC 4472 (M49), located at a distance of <span>(sim )</span>16.7 Mpc in the equatorial constellation of Virgo. Utilizing all available Chandra data observed using the ACIS-S detector from the year 2000 to the year 2021, we identified a total of 57 X-ray point sources, each with data counts <span>(gtrsim )</span>100. From the spectral study, we found 8 ultraluminous X-ray sources (ULXs) and 49 X-ray binaries (XRBs). Among the ULXs, source X-1 was found to be an extremely luminous X-ray source (ELXs) with bolometric luminosity, <span>(L_x sim 10^{40})</span> erg s<span>(^{-1})</span>, probably accreting at a super-Eddington rate. We also detected a super-soft source, X-3, accreting at <span>(sim )</span>0.05 times the Eddington limit, with a disk temperature of <span>(KT_{in} sim 0.25^{+0.06}_{-0.05})</span> keV. Assuming a disk blackbody model, the estimated black hole mass is <span>({sim } 5.57^{+8.89}_{-3.10} times 10^2 M_{odot })</span>, placing it as a possible intermediate-mass black hole (IMBH) candidate. Source X-4 showed notable variability in luminosity, which closely correlated with changes in its inner disk temperature. Its luminosity increased as the disk temperature rose, and decreased as the temperature dropped. A similar trend was also observed in source X-14, although with comparatively less variation in luminosity. Most of the other ULXs in this study remained in a hard spectral state with consistent luminosity across observations, with the exception of source X-34, which displayed spectral variability, and source X-50, which was observed in a soft thermal state. Further, the majority of the detected X-ray binaries were found in a hard spectral state. While four of the XRBs exhibited a soft state and another four showed spectral transitions, their luminosities remained relatively stable. A color–color analysis of the X-ray sources revealed that both XRBs and ULXs generally reside within the low-mass X-ray binary (LMXB) region, albeit with enhanced spectral hardness. Notably, source X-1 displayed even greater hardness, potentially due to its higher luminosity.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145612313","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":"Development of a Compton imager setup","authors":"Anuraag Arya,&nbsp;Harmanjeet Singh Bilkhu,&nbsp;Sandeep Vishwakarma,&nbsp;Hrishikesh Belatikar,&nbsp;Varun Bhalerao,&nbsp;Abhijeet Ghodgaonkar,&nbsp;Jayprakash G. Koyande,&nbsp;Aditi Marathe,&nbsp;N. P. S. Mithun,&nbsp;Sanjoli Narang,&nbsp;Sudhanshu Nimbalkar,&nbsp;Pranav Page,&nbsp;Sourav Palit,&nbsp;Arpit Patel,&nbsp;Amit Shetye,&nbsp;Siddharth Tallur,&nbsp;Shriharsh Tendulkar,&nbsp;Santosh Vadawale,&nbsp;Gaurav Waratkar","doi":"10.1007/s12036-025-10110-7","DOIUrl":"10.1007/s12036-025-10110-7","url":null,"abstract":"<div><p>Hard X-ray photons with energies in the range of hundreds of keV typically undergo Compton scattering when they are incident on a detector. In this process, an incident photon deposits a fraction of its energy at the point of incidence and continues onwards with a change in direction that depends on the amount of energy deposited. By using a pair of detectors to detect the point of incidence and the direction of the scattered photon, we can calculate the scattering direction and angle. The position of a source in the sky can be reconstructed using many Compton photon pairs from a source. We demonstrate this principle in the laboratory by using a pair of Cadmium Zinc Telluride (CZT) detectors sensitive in the energy range of 20–200 keV, similar to those used in <i>AstroSat</i>/CZT Imager (CZTI). The laboratory setup consists of two detectors placed perpendicular to each other in a lead-lined box. The detectors are read out by a custom-programmed Xilinx PYNQ-Z2 FPGA board, and data are then transferred to a personal computer (PC). There are two key updates from CZTI: the detectors are read concurrently rather than serially, and the time resolution has been improved from 20 to 7.5 <span>(mu )</span>s. We irradiated the detectors with a collimated <span>(^{133} texttt {Ba})</span> source and identified Compton scattering events for the 356 keV line. We run a Compton reconstruction algorithm to correctly infer the location of the source in the detector frame, with a location-dependent angular response measure of 16<span>(^circ )</span>–30<span>(^circ )</span>. This comprises a successful technology demonstration for a Compton imaging camera in the hard X-ray regime. We present the details of our setup, the data acquisition process, and software algorithms, and showcase our results. We also quantify the limitations of this setup and discuss ways of improving the performance in future experiments.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145456406","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 possible correlation between cluster lifetime and its number density","authors":"SUSHMITA DEB,&nbsp;BIMAN J. MEDHI,&nbsp;SAMRAT BISWAS","doi":"10.1007/s12036-025-10101-8","DOIUrl":"10.1007/s12036-025-10101-8","url":null,"abstract":"<div><p>In this study, we present our scientific approach to observationally infer possible correlations of the disruption age with the stellar surface density and two-dimensional radius for 200 open star clusters within the solar neighbourhood. A detailed statistical analysis of number density, core and tidal radius, mass, and log(age) has also been presented using the Gaia EDR3 database. The initial mass and disruption time of the individual clusters are calculated using the analytical relations available in the literature, considering the cluster mass loss mechanism due to stellar evolution and tidal interactions. Considering the mass loss models used in this study, we also observe the variation of the initial mass of the star clusters as a function of their present age. We carry out a linear fit for the variation of the cluster disruption time with its number density, which gives an approximate correlation of the form, <span>(t_{textrm{dis}}propto rho _{o}^{0.230pm 0.052})</span>. We also assess this linear relation using statistical correlations, which results in a moderate coefficient value of 0.3903. This statistical correlation and the power law relation illustrate that disruption time increases with the increasing stellar surface density of the cluster. We also observationally and statistically investigate the correlation between the radius and disruption time of the clusters, but no prominent dependence was found between them.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145405654","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":"Characterizing proton polytropic indices inside near-Earth magnetic clouds and ICME sheaths","authors":"Debesh Bhattacharjee,&nbsp;Saikat Majumder,&nbsp;Prasad Subramanian","doi":"10.1007/s12036-025-10103-6","DOIUrl":"10.1007/s12036-025-10103-6","url":null,"abstract":"<div><p>The thermodynamics of interplanetary coronal mass ejections (ICMEs) is often described using a polytropic process. Estimating the polytopic index (<span>(gamma )</span>) allows us to quantify the expansion or compression of the ICME plasma arising from changes in the plasma temperature. In this study, we estimate <span>(gamma )</span> for protons inside the magnetic clouds (MCs), their associated sheaths, and ambient solar wind for a large sample of well-observed events observed by the Wind spacecraft at 1 AU. We find that <span>(gamma )</span> shows a high (<span>({approx }1.6)</span>) – low (<span>({approx } 1.05)</span>) – high (<span>({approx }1.2)</span>) behavior inside the ambient solar wind, sheath, and MCs, respectively. We also find that the proton polytropic index is independent of small-scale density fluctuations. Furthermore, our results show that the stored energy inside MC plasma is not expended in expanding its cross-section at 1 AU. The sub-adiabatic nature of MC plasma implies external heating – possibly due to thermal conduction from the corona. We find that the heating gradient per unit mass from the corona to the protons of MC at 1 AU is <span>({approx } 0.21)</span> erg cm<span>(^{-1})</span> g<span>(^{-1})</span>, which is in agreement with the required proton heating budget.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145406477","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":"Seismic test of the mass-radius relationship of hydrogen-atmospheric white dwarf stars","authors":"Tianqi Cang,&nbsp;Jiayi Zhang,&nbsp;Jian-Ning Fu,&nbsp;He Zhao,&nbsp;Weikai Zong","doi":"10.1007/s12036-025-10106-3","DOIUrl":"10.1007/s12036-025-10106-3","url":null,"abstract":"<div><p>The pulsation of white dwarfs provides crucial information on stellar parameters for understanding the atmosphere and interior structure of these stars. In this study, we present a comprehensive statistical analysis of known ZZ Ceti stars from historical literature. Our dataset includes stellar parameters and oscillation properties from 339 samples, with 194 of them having undergone asteroseismological analysis. We investigated the empirical instability strip of ZZ Ceti stars and confirmed the linear relationship between temperature and weighted mean pulsation periods (WMP). We found that the WMP distribution is well-described with two groups of stars with peak values at <span>({sim }254)</span> and <span>({sim }719)</span> s. Using seismic mass and trigonometrical radii derived from GAIA DR3 parallaxes, we tested the mass-radius relationship of white dwarfs through observational and seismic analysis of ZZ Cetis. They are generally larger than the theoretical values, with the discrepancy reaching up to <span>({sim }15)</span>% for massive stars with a mass estimated by seismology.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145406032","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":"SWASTi: A physics-based modelling toolkit for space weather","authors":"Prateek Mayank,&nbsp;Jithu J. Athalathil,&nbsp;Sirsha Nandy,&nbsp;Bhargav Vaidya,&nbsp;A. V. Navanit,&nbsp;Arghyadeep Paul","doi":"10.1007/s12036-025-10107-2","DOIUrl":"10.1007/s12036-025-10107-2","url":null,"abstract":"<div><p>Space weather poses significant risks to technical systems and the global economy, making it a critical area of research. Coronal mass ejections (CMEs) are the primary drivers of space weather and can cause intense geomagnetic disturbances. The solar wind (SW) governs CME propagation in the heliosphere and drives geomagnetic storm activities. Understanding the evolution of SW stream interaction regions (SIRs), CMEs, and their interactions in the inner heliosphere is essential for accurately predicting their arrival times and mitigating their impacts. This study presents a review of Space Weather Adaptive Simulation (SWASTi), an indigenous three-dimensional magnetohydrodynamic (MHD) modelling framework, with a focus on its SW and CME modules. Comparative analysis with <i>in situ</i> observations demonstrates the model’s robustness, revealing the significant role of ambient SW conditions in shaping the morphological and dynamical properties of CMEs. The geo-effective impact of CME-CME interactions are also explored with a particular focus on the recent Gannon storm. Furthermore, the study discusses how <i>in situ</i> measurements from the Aditya-L1 mission can synergise with the SWASTi framework. This integrated approach, leveraging Aditya-L1 data and SWASTi’s 3D MHD simulations, provides new insights into the complex behaviour of solar wind, SIRs, and CMEs, promising significant advancements in near-real-time space weather forecasting.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145352306","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":"Reconstruction of cosmic ray air shower core location at SURA experiment","authors":"Fatemeh Latifian,&nbsp;Gohar Rastegarzadeh","doi":"10.1007/s12036-025-10098-0","DOIUrl":"10.1007/s12036-025-10098-0","url":null,"abstract":"<div><p>The Semnan University Radio Array (SURA) is a self-triggered radio array located on the roof of the Physics Faculty at Semnan University in Iran. It is designed to detect radio emissions from air showers generated by ultra-high energy (UHE) cosmic rays with energies exceeding <span>(10^{17})</span> eV. The array consists of 4 Log-Periodic Dipole Antennas (LPDAs) operating in the 40–80 MHz range. In this study, we present a method for reconstructing the core location of extensive air showers (EAS) by comparing the signal intensities of simulated and experimental data. We employ a simulated dense array as a reference and determine the core location by matching the experimental signal intensity of each antenna with the corresponding reference antenna in the simulated dense array. The method is first validated using simulated events to estimate its accuracy. We then apply it to the cosmic ray candidates detected by the SURA. Our results show that the core location can be reconstructed with a minimum error of about 3 m. However, when the characteristics of the shower being reconstructed differ significantly from the reference array, the error increases. To enhance reconstruction precision and computational efficiency, we explore optimizations, including reducing the dense array size and accounting for variations in primary energy and arrival direction. Our findings demonstrate the potential of radio-based techniques for high-precision core location reconstruction, providing valuable insights for future large-scale cosmic ray observatories.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 2","pages":""},"PeriodicalIF":1.6,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145316245","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}