Journal of Astrophysics and Astronomy最新文献

{"title":"Stellar contents and star formation in IRAS 18456-0223","authors":"Nilesh Pandey,&nbsp;U. S. Kamath","doi":"10.1007/s12036-026-10148-1","DOIUrl":"10.1007/s12036-026-10148-1","url":null,"abstract":"<div><p>We use various analytical techniques to study Young Stellar Objects (YSOs) in an area of approximately <span>(10~^{prime }times 10~^{prime })</span> in the IRAS 18456-0223 star-forming region. We use archival optical (<i>Gaia DR3</i>) and infrared (<i>2MASS</i>, <i>UKIDSS</i>, <i>Spitzer</i>, <i>WISE</i>, and <i>Herschel</i>) data and our optical spectroscopy of three bright stars for this purpose. We identify 89 YSOs (80 class II and 9 class I), based on their infrared properties. Our multiwavelength SED fits of select YSOs show that they have masses <span>(sim 0.1)</span>–7.2 <span>(M_odot )</span> and are upto 4 Myr old. Our Minimum Spanning Tree (MST) analysis shows that these YSOs, situated at around 600 pc, form clusters with radial extent of order <span>(0.5,textrm{pc})</span> and mean surface densities <span>(sim 60,textrm{pc}^{-2})</span>. We compare <i>UKIDSS</i> and <i>2MASS</i> data of the YSOs and find that some of them show variability. We constructed maps based on <i>Herschel</i> data which reveal multiple column density peaks (<span>(N_{mathrm{H_2}}sim 10^{22},textrm{cm}^{-2})</span>) embedded in cold (<span>(T_d sim 10{-}13)</span> K) filaments. Our near-infrared extinction map exhibits several high-<span>(A_V)</span> peaks, some of which coincide with the sub-mm column density maxima. Using our optical spectra of three bright sources, we show that they are of A-K type. One star shows the Li I 6707 Å  line, indicating its youth.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737620","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":"Modeling natal kicks in the formation of binary pulsars: Impact on the orbital dynamics and population characteristics","authors":"Ali Taani","doi":"10.1007/s12036-026-10131-w","DOIUrl":"10.1007/s12036-026-10131-w","url":null,"abstract":"<div><p>Kick velocities produced during accretion induced collapse (AIC) can substantially alter the dynamics of binary pulsars. Here we examine how these kicks reshape post-AIC orbits and identify the conditions under which binaries survive this event. We modeled the orbital response by requiring that the companion’s location at the moment of collapse be consistent with both the pre- and post-kick trajectories. Monte Carlo simulations of 10000 binaries show that modest kicks of 10 to 100 km/s reproduce the observed population spread in the orbitals of close binaries. Post-AIC periods show that the ratio of the two depends sensitively on kick amplitude and the induced eccentricity. Roughly 23% of binaries with present day periods below 2d originate from compact pre-AIC systems of similar scale. Systems experiencing kicks <span>(le )</span> 50 km/s remain bound with high probability, whereas stronger kicks disrupt a large fraction of binaries. significant orbital evolution driven by the AIC process and its role in shaping the population of short-period binary pulsars. These results clarify the dynamical pathways through which AIC contributes to neutron star formation and the diversity of binary pulsar orbits.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147642723","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":"‘Bursts, beats, and beyond’: uncovering the landscape from accretion to ignition of 4U 1728–34 using AstroSat","authors":"Anirudh Salgundi,&nbsp;Suman Bala,&nbsp;Gayathri Raman,&nbsp;Utkarsh Pathak,&nbsp;Varun Bhalerao","doi":"10.1007/s12036-025-10124-1","DOIUrl":"10.1007/s12036-025-10124-1","url":null,"abstract":"<div><p>A comprehensive study on persistent and thermonuclear burst emission of 4U 1728–34, commonly known as ‘Slow Burster’, is performed using seven archival observations of <i>AstroSat</i> spanning from 2016 to 2019. The burst-free persistent spectra can be well fitted with a blackbody (<span>bbody</span>) and a powerlaw (<span>powerlaw</span>) components, with a powerlaw photon index (<span>(Gamma )</span>) found to be <span>(sim )</span>2, indicating the source was in ‘high/soft’ banana state or intermediate state. The time-averaged power density spectrum reveals the presence of twin kilohertz Quasi Periodic Oscillations (kHz QPOs) with centroid frequencies <span>(619pm 10)</span> and <span>(965pm 6)</span> Hz with a maximum fractional root mean squared amplitude of <span>(6.24pm 1.31)</span>% at <span>(sim )</span>16 keV. From the upper kHz QPO, we infer the magnetospheric disk radius to be <span>(sim )</span>17 km, corresponding to a magnetic field strength of 0.35–<span>(1.27times 10^7)</span> G. The burst spectral evolution indicates Photospheric Radius Expansion (PRE) in five bursts, yielding a touchdown radius of 3.1–5.47 km. These bursts reached near-Eddington luminosities, through which the distance of the source was calculated to be 5.18–5.21 kpc. Two of the bursts show coherent oscillations at 362.81–363.93 Hz. The presence of twin kHz QPOs and coherent Burst Oscillations allows us to provide two different estimates for the spin frequency of the Neutron Star in the system, for the first time using <i>AstroSat</i>.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606503","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 galaxy cluster environment on the stellar mass function of galaxies","authors":"SANA BEGUM MURTUJA SHAIKH,&nbsp;PRIYANKA SINGH","doi":"10.1007/s12036-026-10140-9","DOIUrl":"10.1007/s12036-026-10140-9","url":null,"abstract":"<div><p>Galaxy clusters represent some of the most extreme environments in the Universe. They are ideal locations to study the impact of an extreme environment on the evolution of the Stellar Mass Function (SMF), which describes the statistical distribution of galaxies as a function of their stellar masses. In this work, we examine how the SMF of galaxies depends on factors such as the surrounding environments, whether they reside in isolated fields or clusters. We use the 9-band photometric galaxy data of the G9 patch from the Kilo Degree Survey (optical) and the VISTA Kilo-Degree Infrared Galaxy Survey (infrared), containing around 3.7 million galaxies, overlapping with the cluster catalog provided by the eROSITA Final Equatorial Depth Surveys (eFEDS). After applying appropriate selection criteria, we have 105 eFEDS clusters within the redshift range 0.385–0.8, covering <span>(sim 46)</span> square degrees. The large, continuous overlap of the surveys allows us to examine the SMF of the cluster galaxies within the cluster-centric radial bins up to <span>(5R_{500})</span>. We find a clear detection of the cluster galaxy SMF up to <span>(2R_{500})</span> beyond which it’s consistent with the background. We divide the cluster sample into redshift, mass, and X-ray luminosity bins to examine their impact on the SMF. The SMF of cluster galaxies for the high-mass clusters shows a decline at low stellar masses (<span>(M_*lesssim 2times 10^{10}M_odot )</span>) within <span>(0-0.5R_{500})</span>, as compared to a flat SMF for the low-mass clusters, suggesting the low-mass galaxies grow over time before reaching the cluster center. Additionally, we find a flatter SMF for the low redshift bin within <span>(0.5R_{500})</span> at stellar masses <span>(M_*&lt; 10^{10}M_odot )</span>. We also examined the effect of cluster ellipticity on the cluster galaxy SMF; however do not find statistically significant differences between the high and the low ellipticity clusters.\u0000</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561719","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 chemodynamical study of r-process-enhanced stars","authors":"Pallavi Saraf,&nbsp;Thirupathi Sivarani,&nbsp;Carlos Allende Prieto,&nbsp;Shashikiran Ganesh,&nbsp;Drisya Karinkuzhi","doi":"10.1007/s12036-026-10142-7","DOIUrl":"10.1007/s12036-026-10142-7","url":null,"abstract":"<div><p>The <i>r</i>-process enrichment in the Galaxy still remains elusive with regard to its nucleosynthesis conditions and the astrophysical sites where it occurs. As part of ongoing efforts to pinpoint the origin of chemically peculiar <i>r</i>-process-enhanced (RPE) stars, we concentrate in this study on the kinematics of RPE stars to investigate possible variations in the <i>r</i>-process enrichment among the Galactic components. We calculate the orbital parameters of a sample of 472 metal-poor RPE stars and associate them to the Galactic bulge, disk and halo populations using a physically motivated classification based on apocenter distance and maximum absolute vertical height of the orbit. We show that the Toomre diagram does not properly separate stars in the disk and halo components when they are on highly eccentric and/or retrograde orbits. The Galactic disk and halo share a similar fraction of RPE stars, in contrast to the earlier perception that the majority of RPE stars belong to the halo. Most of the RPE stars are located within the mixed zone of the action-space diagram, with only about 10% exhibiting clear accretion-like dynamics. The inner disk, inner halo and outer halo stars exhibit similar abundance trends for the n-capture elements.\u0000</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561720","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":"One Year of ASPEX-STEPS Operation: Characteristic Features, Observations and Science Potential","authors":"Jacob Sebastian,&nbsp;Bijoy Dalal,&nbsp;Aakash Gupta,&nbsp;Shiv Kumar Goyal,&nbsp;Dibyendu Chakrabarty,&nbsp;Santosh V. Vadawale,&nbsp;M. Shanmugam,&nbsp;Neeraj Kumar Tiwari,&nbsp;Arpit R. Patel,&nbsp;Aveek Sarkar,&nbsp;Aaditya Sarda,&nbsp;Tinkal Ladiya,&nbsp;Prashant Kumar,&nbsp;Manan S. Shah,&nbsp;Abhishek Kumar,&nbsp;Shivam Parashar,&nbsp;Pranav R. Adhyaru,&nbsp;Hiteshkumar L. Adalja,&nbsp;Piyush Sharma,&nbsp;Abhishek J. Verma,&nbsp;Nishant Singh,&nbsp;Sushil Kumar,&nbsp;Deepak Kumar Painkra,&nbsp;Swaroop B. Banerjee,&nbsp;K. P. Subramaniam,&nbsp;Bhas Bapat,&nbsp;M. B. Dadhania,&nbsp;P. Janardhan,&nbsp;Anil Bhardwaj","doi":"10.1007/s12036-026-10134-7","DOIUrl":"10.1007/s12036-026-10134-7","url":null,"abstract":"<div><p>The SupraThermal and Energetic Particle Spectrometer (STEPS), a subsystem of the Aditya Solar wind Particle EXperiment (ASPEX) onboard India’s Aditya-L1 satellite, is designed to study different aspects of energetic particles in the interplanetary medium from the Sun-Earth L1 point using six detector units oriented in different directions. This article presents details of the one-year operation (08 January 2024 - 28 February 2025) of the AL1-ASPEX-STEPS after the insertion of the satellite into the final halo orbit around the L1 point with emphasis on performance, science observations, and scientific potentials. Four out of six AL1-ASPEX-STEPS units exhibit a stable detector response throughout the observation period, confirming operational robustness. This work also includes the temporal variation of particle differential directional fluxes (DDFs), spectra of ions during selected quiet times and transient events, and cross-comparisons with existing instruments at the L1 point. A strong correlation (with coefficient of determination, R<span>(^2 approx )</span> 0.9) is observed in the cross-comparison study, establishing the reliability of the AL1-ASPEX-STEPS observations. AL1-ASPEX-STEPS also captures different forms of energetic ion spectra similar to those observed by previous missions. These results underscore the instrument’s potential to contribute significantly to the study of energetic particle acceleration, transport, and long-term space weather monitoring from the Sun–Earth L1 vantage point.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561199","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":"Late time cosmic acceleration in a novel (f(R)) gravity theory with dynamic stability, thermodynamic consistency and screening mechanisms","authors":"C Sivakumar","doi":"10.1007/s12036-026-10145-4","DOIUrl":"10.1007/s12036-026-10145-4","url":null,"abstract":"<div><p>The observed late-time acceleration of the universe remains one of the most profound puzzles in modern cosmology. While the standard approach attributes this acceleration to an unknown dark energy component within the framework of General Relativity, modified gravity theories-particularly <i>f</i>(<i>R</i>) gravity-have emerged as compelling alternatives that do not invoke exotic matter fields. In this work, we propose a new <i>f</i>(<i>R</i>) gravity model of the form <span>(f(R)=R+frac{gamma {R}^frac{{1}}{n}}{1+mu {R}^frac{{1}}{n}})</span> where γ, μ and n are model parameters. For small curvature, this model effectively behaves as <span>(f(R)approx R+gamma {R}^frac{{1}}{n})</span>, allowing the curvature modification to mimic a dynamically evolving dark energy component with <span>({rho }_{DE}propto {a}^{-frac{2}{np}})</span>, which drives late-time acceleration, particularly <span>({rho }_{DE}propto {a}^{-1})</span> for <span>(np=2)</span>, by assuming a power-law behaviour for scale factor. At high curvature, the correction term is suppressed, ensuring the model closely approximates General Relativity and enables a chameleon-like screening mechanism that satisfies local gravity constraints. We derive the modified Friedmann equations in a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) background and analyse the cosmological dynamics driven by the proposed model. Through analytical techniques, we investigate the conditions under which the model produces late cosmic acceleration without introducing a cosmological constant. We also examine the behaviour of the effective equation of state and demonstrate the physical viability of the model by comparing its predictions with current observational data and applying various stability tests, including a thermodynamic analysis. Our findings suggest that the proposed model is a viable alternative to dark energy, consistent with both cosmological and solar system constraints.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561196","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 hidden cosmic highways: stability and orbital dynamics of quasi-Lagrangian points in the Kepler-1625 exoplanetary system","authors":"Tapomugdha Mandal","doi":"10.1007/s12036-026-10141-8","DOIUrl":"10.1007/s12036-026-10141-8","url":null,"abstract":"<div><p>This research investigates the complex gravitational dynamics of the Kepler-1625 exoplanetary system by modeling the interactions among the host star, a massive exoplanet, its candidate Neptune-sized exomoon, and a test particle within an extended restricted four-body framework. Building upon the generalized restricted four-body problem, we analytically derive and numerically locate quasi-Lagrangian points (QLPs) that extend classical equilibrium concepts to this more intricate setting. Utilizing canonical normalization and system-specific parameterization, we perform comprehensive numerical simulations encompassing trajectory tracking, spectral and resonance analyses, gravitational potential characterization, and tidal force computations. Our results identify distinct stable and unstable QLPs, reveal underlying resonance structures and chaotic behaviors, and quantify tidal stresses that potentially impact exomoon orbital evolution and internal heating. This integrative approach advances theoretical understanding and provides practical insights for future observational and mission endeavors aimed at detecting and characterizing exomoons in complex multi-body systems like Kepler-1625.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561197","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":"Abundance stratification in type Iax SN 2020rea with TARDIS","authors":"Sohini Kayal,&nbsp;P Gayatri,&nbsp;Mridweeka Singh,&nbsp;Kuntal Misra","doi":"10.1007/s12036-026-10136-5","DOIUrl":"10.1007/s12036-026-10136-5","url":null,"abstract":"<div><p>Using the 1D Monte Carlo–based radiative transfer code <span>TARDIS</span>, we investigate the spectral evolution of the Type Iax supernova (SN) 2020rea from − 7 days before to + 21 days after maximum light. Our best-fit models indicate stratified, velocity-dependent abundances at early times, successfully reproducing most observed spectral features. As the SN evolves, the ejecta transition from a layered to a more homogeneous composition, posing an alternative to pure deflagration models that predict fully mixed ejecta. These results highlight the need for further investigation, as current pure deflagration models cannot fully explain the origin or spectral properties of Type Iax SNe like SN 2020rea.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561195","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":"Low redshift observational constraints on dark energy models using ANN – CosmicANNEstimator","authors":"Ashly Joseph,&nbsp;Albin Joseph,&nbsp;Christina Terese Joseph,&nbsp;John Paul Martin,&nbsp;P. V. Sunil Kumar,&nbsp;Sarthak Giri","doi":"10.1007/s12036-025-10121-4","DOIUrl":"10.1007/s12036-025-10121-4","url":null,"abstract":"<div><p>We present Cosmological Parameters Artificial Neural Network Estimator (CosmicANNEstimator), a machine learning approach for constraining cosmological parameters within the Lambda Cold Dark Matter (<span>(Lambda )</span>CDM) framework. Our methodology employs two specialised artificial neural networks (ANNs) designed to analyse Hubble parameter and Supernova data independently. The estimator is trained on synthetic datasets encompassing diverse parameter ranges, with Gaussian random noise incorporated to simulate observational uncertainties. Our results demonstrate parameter estimates and associated uncertainties comparable to traditional Markov Chain Monte Carlo (MCMC) methods, establishing machine learning as an efficient alternative for cosmological parameter estimation. This work underscores the potential of neural network-based inference to complement traditional Bayesian methods and accelerate future cosmological analyses.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"47 1","pages":""},"PeriodicalIF":1.6,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560671","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}