Journal of Astrophysics and Astronomy最新文献

{"title":"One year of ASPEX-SWIS operation: characteristic features, observations and science potential","authors":"Abhishek Kumar,&nbsp;Shivam Parashar,&nbsp;Prashant Kumar,&nbsp;Dibyendu Chakrabarty,&nbsp;Bhas Bapat,&nbsp;Aveek Sarkar,&nbsp;Manan S. Shah,&nbsp;Hiteshkumar L. Adalja,&nbsp;Arpit R. Patel,&nbsp;Pranav R. Adhyaru,&nbsp;M. Shanmugam,&nbsp;Swaroop B. Banerjee,&nbsp;K. P. Subramaniam,&nbsp;Tinkal Ladiya,&nbsp;Jacob Sebastian,&nbsp;Bijoy Dalal,&nbsp;Aakash Gupta,&nbsp;M. B. Dadhania,&nbsp;Santosh V. Vadawale,&nbsp;Shiv Kumar Goyal,&nbsp;Neeraj Kumar Tiwari,&nbsp;Aaditya Sarda,&nbsp;Sushil Kumar,&nbsp;Nishant Singh,&nbsp;Deepak Kumar Painkra,&nbsp;Piyush Sharma,&nbsp;Abhishek J. Verma,&nbsp;P. Janardhan,&nbsp;Anil Bhardwaj","doi":"10.1007/s12036-026-10155-2","DOIUrl":"10.1007/s12036-026-10155-2","url":null,"abstract":"<div><p>The Aditya-L1 mission, India’s first dedicated solar observatory at the first Lagrange point of the Sun-Earth system, carries the Solar Wind Ion Spectrometer (SWIS) as part of the Aditya Solar Wind Particle Experiment (ASPEX) payload suite. Even before settling down at the Halo orbit, AL1-ASPEX-SWIS has been delivering nearly continuous in situ measurements of solar wind ion spectra. Moments of the velocity distribution function (VDFs) have been calculated to derive the solar wind bulk parameters like density, bulk speed, temperature etc. Through this work, we evaluate the performance of AL1-ASPEX-SWIS through comparisons with contemporaneous measurements from the Wind and DSCOVR spacecrafts. A detailed case study of the 07 August 2024 interplanetary coronal mass ejection (ICME) is presented where sharp transitions in bulk speed, thermal speed, and number density were well-aligned with independent observations, confirming the instrument’s capability in capturing dynamic solar wind features. Spectral analysis of kinetic fluctuations revealed a well-defined inertial range with a spectral slope consistent with magnetohydrodynamic (MHD) turbulence. Additionally, a 17-month statistical comparison (January 2024–May 2025) shows strong agreement in bulk velocity (<span>(R^2 approx 0.94)</span> with Wind), with expected variability in thermal speed and density due to inter-instrument differences. These results confirm the scientific utility of AL1-ASPEX-SWIS in monitoring both transient events and long-term solar wind conditions.</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":"148751738","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":"Model independent probe of variation of cosmic opacity with redshift","authors":"Savita Gahlaut,&nbsp;Meetu Luthra","doi":"10.1007/s12036-026-10169-w","DOIUrl":"10.1007/s12036-026-10169-w","url":null,"abstract":"<div><p>Cosmic opacity may vary spatially due to the inhomogeneous distribution of dust, its grain properties, and the efficiency of photon attenuation. In this work, we present a model independent method to investigate the variation of cosmic opacity with redshift. Using strong gravitational lensing data we construct the opacity independent comoving distance function and we use latest supernovae type Ia (SNe Ia) Pantheon+ data to estimate the opacity dependent comoving distances. Using the distance duality equation, opacity parameter is constrained. Our analysis indicates a transparent Universe on average over the redshift range (<span>(0.01 le z le 2.26137)</span>) of Pantheon+ sample. However, if we split the dataset into subsamples with redshift bins of width <span>(bigtriangleup z = 0.1)</span>, we find appreciable deviation from the transparency in several redshift intervals. Particularly, in the redshift range <span>(0.3 &lt; z le 0.4)</span>, the opacity parameter is <span>(epsilon = -0.4283^{+0.1914}_{-0.2027})</span>. The current SNe Ia observations indicate the variation of opacity parameter with redshift. These results may have a significant impact on the values of the cosmological parameters deduced from the SNe Ia observations.</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":"148751882","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":"Propagation characteristics of the April 21, 2023 CME","authors":"Sandeep Kumar,&nbsp;Nandita Srivastava,&nbsp;Parthib Banerjee,&nbsp;Nat Gopalswamy","doi":"10.1007/s12036-026-10149-0","DOIUrl":"10.1007/s12036-026-10149-0","url":null,"abstract":"<div><p>Accurate estimation of propagation characteristics of coronal mass ejections (CMEs) is crucial for predicting their geoeffectiveness. Stereoscopic techniques to study the kinematics of CMEs generally have been carried out using remote sensing observations from three viewpoints, i.e. STEREO-A, STEREO-B, and SOHO. Since the loss of STEREO-B in 2014, stereoscopic reconstruction of CMEs has been restricted to the observations from only two viewpoints, i.e., STEREO-A and SOHO. When the angle of separation between STEREO-A and SOHO is small, it leads to larger uncertainties in the CME kinematics derived using stereoscopic techniques. In this paper, we demonstrate how this limitation can be addressed and how uncertainties in the estimation of CME kinematics and propagation direction can be reduced. For this purpose, we selected the CME of April 21, 2023, which was observed by two spacecraft, i.e. STEREO-A and SOHO, separated by a small <span>(10^circ )</span> angle. Using the Graduated Cylindrical Shell (GCS) model on the remote-sensing observations near the Sun and the Advanced Drag-Based Model (ADBM) in the heliosphere, we estimated the arrival time of the CME at different locations in the heliosphere and compared it with the actual arrival time obtained from the in-situ measurements taken by three spacecraft, BepiColombo, STEREO-A and Wind. Our analysis reveals a directional uncertainty of approx <span>(20 ^circ )</span> from observations from two viewpoints. These uncertainties significantly affect the arrival-time prediction of the CME. We consider the actual chronology of CME arrival times at STEREO-A and Wind as critical parameters to constrain the direction of propagation, which serves as a key input in the ADBM. The chronology of arrival of the CME ejecta at STEREO-A, which is 4.5 hrs earlier than at Wind, proved essential for resolving directional ambiguities in the GCS reconstruction model.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751379","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":"Compact and physically interpretable feature models for photometric type Ia supernova classification","authors":"Anurag Garg","doi":"10.1007/s12036-026-10175-y","DOIUrl":"10.1007/s12036-026-10175-y","url":null,"abstract":"<div><p>Photometric classification of Type Ia supernovae is essential for modern time-domain surveys, where spectroscopic confirmation is not always feasible for the full transient sample. In this work, we investigate a compact and physically interpretable feature representation derived from multi-band light curves and evaluate its performance using gradient-boosted decision trees on the Supernova Photometric Classification Challenge (SPCC) dataset. The compact representation is derived from an initial pool of 31 light-curve features, reduced to 30 after removing redundant variables, and further optimized to a 16-feature model using systematic ablation and performance analysis. The final compact model achieves an F1–score of 0.844 on the held-out test set. This is consistent with k-fold cross-validation results (0.841 ± 0.006). The precision–recall area under the curve (PR-AUC) is 0.928, with similarly low variance across folds. Relative to our earlier 31-feature optimized XGBoost model for the same SPCC classification task (F1 <span>(approx )</span> 0.923), the compact 16-feature representation retains strong classification performance (F1 = 0.844) while substantially improving interpretability and reducing feature-space complexity. The ablation results show that temporal evolution provides the dominant classification signal, while brightness, color, and variability features supply complementary information. A reduced core of approximately ten physically meaningful features retains a large fraction of the performance of the compact model, with only a small decrease in F1-score, indicating that reliable classification does not require large high-dimensional feature spaces. These results demonstrate that interpretable feature-based models can capture the essential astrophysical information needed for Type Ia photometric classification, with direct implications for survey cadence, filter coverage, and the design of transparent and efficient machine learning pipelines for future time-domain surveys.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751378","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":"Aditya-L1/VELC observations of CME associated broadening of 5303Å coronal emission line","authors":"K Sasikumar Raja,&nbsp;V Muthu Priyal,&nbsp;R Ramesh,&nbsp;Jagdev Singh,&nbsp;Prasad Subramanian","doi":"10.1007/s12036-026-10164-1","DOIUrl":"10.1007/s12036-026-10164-1","url":null,"abstract":"<div><p>We present Aditya-L1/VELC spectroscopic observations of 5303Å coronal emission line widths before and after coronal mass ejections (CMEs) which showed coronal dimming. The sit &amp; stare mode of observations enabled us to study the changes in the line widths for the ‘limb’ CMEs noticed on 16 July 2024 and 05 August 2024. The emission line widths during the pre-CME phase are higher than the thermal values in both the cases. After the onset of the CMEs, the widths increased further by <span>({approx }15%)</span> on 16 July 2024 and <span>({approx }7%)</span> on 05 August 2024. We find that the power spectral density (PSD) distributions of the line widths for the two events exhibits a power-law behavior. The PSD slopes, measured before and after the CMEs are nearly the same, and close to the Kolmogorov slope of <span>({-5/3})</span>. The results suggest that the observed larger than thermal width of the 5303Å emission line, before and after CMEs, is mostly due to turbulence. The additional increase in the line widths after the onset of the CMEs in both the cases are likely because of enhanced turbulence caused by the CME associated coronal dimmings and subsequent coronal magnetic field reconfiguration.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613615","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":"Subcritical dynamos: a tutorial and review","authors":"Paul Charbonneau","doi":"10.1007/s12036-026-10166-z","DOIUrl":"10.1007/s12036-026-10166-z","url":null,"abstract":"<div><p>Various lines of evidence are pointing to the possibility that the dynamo mechanism powering the solar magnetic activity cycle may be operating very close to, or even below, criticality. Such evidence includes the sudden drop in angular momentum loss in magnetized winds inferred in solar-type stars slighty older than the sun, and the ability of dynamos operating at or very close to criticality to generate solar-like patterns of long-term amplitude modulation when subjected to (relatively) weak stochastic forcing. After reviewing the notions of subcriticality, criticality and supercriticality in the context of the classical mean-field <span>(alpha Omega )</span> dynamo model, I review the broader extant literature on the topic and present a simple model based on energetics that provides upper bounds on the finite amplitude sustained by an otherwise subcritical large-scale “primary” dynamo in the presence of a secondary dynamo process. This allows new scenarios for intermittency, which are presented and discussed in qualitative terms, together with implications for our understanding of long-term solar cycle variability.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613616","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":"pyTANSPEC-v1.0 and HxRGproc: updated packages to clean and reduce TANSPEC data","authors":"Varghese Reji,&nbsp;Joe P. Ninan,&nbsp;Supriyo Ghosh,&nbsp;Devendra K. Ojha,&nbsp;Saurabh Sharma","doi":"10.1007/s12036-026-10163-2","DOIUrl":"10.1007/s12036-026-10163-2","url":null,"abstract":"<div><p>TIFR-ARIES near-infrared spectrometer (TANSPEC) is a spectrograph-cum-imager operating over the wavelength range <span>(0.55{-}2.5~mu )</span>m. The instrument is mounted on the 3.6-m devasthal optical telescope (3.6-m DOT). It offers two resolution modes: low resolution (LR) and cross-dispersed (XD) via various slits of different widths (0.5”, 0.75”, 1.0”, 1.5”, 2.0” and 4.0”). The LR mode provides a resolving power (<i>R</i>) of <span>(sim 100{-}350)</span>, while the XD mode achieves <span>(Rsim 2500)</span> using the 0.5” slit. The previous version of the data reduction pipeline supported only wavelength-calibrated XD mode spectra and was limited to two slits (S-0.5 and S-1.0). In this work, we present an upgraded version of <span>pyTANSPEC</span>. The upgraded pipeline not only improves the data extraction algorithm but also introduces several new features for users. It now enables the reduction of spectra from all available slits for both LR and XD modes. The upgraded version also implements a template-matching method for more precise wavelength calibration. Additionally, a step for flux calibration is also included. Alongside <span>pyTANSPEC</span>, we upgraded <span>HxRGproc</span>, a Python package for cleaning and generating slope images from non-destructive readout frames taken with H1RG and H2RG detectors. The package performs non-linearity correction, flags saturated pixels, removes pink noise, and eliminates cosmic ray events. <span>HxRGproc</span> is updated to work for the H2RG detector of TANSPEC and is set up on the TANSPEC server, ensuring users receive data that are pre-cleaned and non-linearity corrected.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613614","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":"Astrolabes as records of previous eruptions of the recurrent nova T Coronae Borealis","authors":"B. S. Shylaja","doi":"10.1007/s12036-026-10162-3","DOIUrl":"10.1007/s12036-026-10162-3","url":null,"abstract":"<div><p>The recurrent nova T Coronae Borealis (T CrB) has recorded eruptions in 1946 and 1866 and a periodicity of 80 years renders the next eruption due shortly. A search for the earlier records of eruption (Schaefer 2023a) provided one as early as 1217 and another in 1787. Here we report the results of search in astrolabes, whose star dials, as we show, serve as unconventional sources of sightings. The catalogues (Gunther 1932; Sarma 2023) list the stars on the dials of astrolabes and provide a rich source of such records, though some pointers are left unidentified and sometimes misidentified by later studies. The procedure adopted for identification is explained with the help of the astrolabe which has the supernova SN1604 recorded to emphasise the difficulty involved. We were able to pinpoint three astrolabes as possible records of eruption of T CrB. The difficulties associated with this procedure and overcoming the disadvantages of poor resolution are discussed. One eruption around 1450CE is identified in a Spanish astrolabe and another sometime around 1570CE. The third is from second half of seventeenth-century. A long-term recurrence period of 82 years seems to be valid in the last eight centuries, putting the next eruption to 2028.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465832","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":"Forecasting horizon Dst index based on solar wind data using deep learning and generative artificial intelligence","authors":"Wihayati,&nbsp;Hindriyanto Dwi Purnomo,&nbsp;Suryasatriya Trihandaru","doi":"10.1007/s12036-026-10158-z","DOIUrl":"10.1007/s12036-026-10158-z","url":null,"abstract":"<div><p>This paper compares Transformer architectures (Bisection Transformer, Bidirectional Encoder Representations from Transformers (BERT), Robustly Optimized BERT Approach (RoBERTa)), Generative Adversarial Networks (GAN), deep learning (Long Short-Term Memory (LSTM), Gated Recurrent Unit (GRU)), and Nonlinear AutoRegressive Moving Average with eXogenous (NARMAX) in forecasting the Disturbance storm-time (Dst) index using solar wind parameters. The purpose of this paper is to emphasize the importance of selecting a specific model for the 5- to 100-step-ahead forecasting horizon across various algorithmic approaches in operational space weather forecasting and geomagnetic storm prediction. In these tests, NARMAX has the lowest Root Mean Square Error (RMSE) of 14.723 at a horizon of 5 for short-term forecasting, but this decreases at longer horizons. In contrast, GAN exhibits consistent performance with minimal decline, increasing RMSE by 7.5% from horizons 5 to 100. Meanwhile, RoBERTa outperforms in the medium-term, achieving its best performance between horizons 20 and 50. Statistical analysis shows that the Transformer architecture outperforms deep learning at longer time horizons.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465504","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":"Main sequence spectral and mass calibrations of effective temperature, absolute magnitude, luminosity, surface gravitational potential, surface gravitational acceleration and radius of B-stars","authors":"S. V. Sinitsyn","doi":"10.1007/s12036-026-10159-y","DOIUrl":"10.1007/s12036-026-10159-y","url":null,"abstract":"<div><p>The known empirical data of the effective temperature and the absolute magnitude of BV-III stars are analyzed. In this regard, the tabular and analytical spectral calibrations of these parameters are determined for these stars. The empirical relations between the luminosity and mass are determined for BV-III stars. In this regard, the tabular spectral calibrations of the mass, the radius, the surface gravitational potential and the surface gravitational acceleration are determined for BV-III stars. Using these tabular calibrations, the analytical mass and spectral calibrations of their parameters are established for these stars. The areas of the constant value of the surface gravitational potential and the areas of the constant value of the surface gravitational acceleration are found in the analytical mass and spectral calibrations of these parameters. The areas of the first type and the areas of the second type alternately follow each other along the axes of the mass and the spectral type. Also, the areas of the first type and the areas of the second type follow with constant the repetition step along the axes of the surface gravitational potential and the surface gravitational acceleration, respectively.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 2","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465296","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}