Journal of Astrophysics and Astronomy最新文献_第2页

Conversion of emitted axionic dark matter to photons for non-rotating magnetized neutron stars

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-29 DOI: 10.1007/s12036-024-10036-6

Shubham Yadav, M. Mishra, Tapomoy Guha Sarkar

引用次数: 0

VolDen: A tool to extract number density from the column density of filamentary molecular clouds

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-27 DOI: 10.1007/s12036-024-10033-9

A. K. Ashesh, Chakali Eswaraiah, P. Ujwal Reddy, Jia-wei Wang

{"title":"VolDen: A tool to extract number density from the column density of filamentary molecular clouds","authors":"A. K. Ashesh, Chakali Eswaraiah, P. Ujwal Reddy, Jia-wei Wang","doi":"10.1007/s12036-024-10033-9","DOIUrl":"10.1007/s12036-024-10033-9","url":null,"abstract":"<div><p>Gas volume density is one of the critical parameters, along with dispersions in magnetic field position angles and non-thermal gas motions, for estimating the magnetic field strength using the Davis–Chandrasekhar–Fermi (DCF) relation or through its modified versions for a given region of interest. We present <span>VolDen</span> an novel python-based algorithm to extract the number density map from the column density map for an elongated interstellar filament. <span>VolDen</span> uses the workflow of <span>RadFil</span> to prepare the radial profiles across the spine. The user has to input the column density map and pre-computed spine along with the essential <span>RadFil</span> parameters (such as distance to the filament, the distance between two consecutive radial profile cuts, etc.) to extract the radial column density profiles. The thickness and volume density values are then calculated by modeling the column density profiles with a Plummer-like profile and introducing a cloud boundary condition. The cloud boundary condition was verified through an accompanying N-PDF column density analysis. In this paper, we discuss the workflow of <span>VolDen</span> and apply it to two filamentary clouds. We chose LDN1495 as our primary target owing to its nearby distance and elongated morphology. In addition, the distant filament RCW57A is selected as the secondary target to compare our results with the published results. Upon publication, a complete tutorial of <span>VolDen</span> and the codes will be available via https://github.com/aa16oaslak/volden.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109768","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}

引用次数: 0

Variability of physical parameters of IRAS 22272(+)5435 during the pulsation cycle

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-27 DOI: 10.1007/s12036-024-10037-5

Laimons Začs, Kārlis Puķītis

引用次数: 0

Exploring daily fluctuations of cosmic ray muon components at a low latitude site and their associations with space weather variables 探索低纬度地点宇宙射线介子成分的日波动及其与空间天气变量的关系

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-17 DOI: 10.1007/s12036-024-10034-8

Maghrabi Abdullrahman, Al Harbi Hya, Alruhaili Aied

{"title":"Exploring daily fluctuations of cosmic ray muon components at a low latitude site and their associations with space weather variables","authors":"Maghrabi Abdullrahman, Al Harbi Hya, Alruhaili Aied","doi":"10.1007/s12036-024-10034-8","DOIUrl":"10.1007/s12036-024-10034-8","url":null,"abstract":"<div><p>In this study, cosmic rays (CR) data from the King Abdulaziz University muon detector in Jeddah (Rc = 14.8 GV), Saudi Arabia, were utilized to investigate the amplitude and phase components of diurnal variations in CR muons. The data covered the period from 2007 to 2012 and were fitted using a single cosine function with a 24-h period and two cosine functions with periods of 24 h and 12 h, respectively. The distributions of the phases and amplitudes resulting from these fits were analyzed across different time spans. </p><p>The findings of this analysis provided valuable insights into the diurnal characteristics of CR muons. The mean amplitude and phase obtained from the single fit were reported as −0.11 ± 0.51% and 11:00 ± 4.30 UT, respectively. Furthermore, employing the two-cosine fit revealed that the first phase had a mean occurrence time of 06:00 ± 6.90 UT, accompanied by an amplitude of −0.10 ± 0.62%. The second phase occurred at 13:00 ± 3.51 UT, with an amplitude of 0.11 ± 0.25%. The study observed diverse distributions and trends in amplitude and phase values across different time scales, including months, seasons, and years. </p><p>Additionally, the study investigated the influences of five solar activity parameters on the diurnal CR components using Pearson linear, non-parametric Spearman, and Kendall correlations. These parameters included the interplanetary magnetic field, solar wind speed, Kp index, Dst index, and solar radio flux at 10.7 cm. The results revealed that the relationships between solar activity variables and the diurnal CR parameters were not uniform. There were varying degrees of correlation, with differences in strength and magnitude depending on the specific variable and correlation coefficient being examined.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142995142","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}

引用次数: 0

Mathematical model as per the algorithm of Sūryasiddhānta for computation of location specific true position of the planets 根据Sūryasiddhānta算法建立的数学模型，计算行星的具体位置

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-09 DOI: 10.1007/s12036-024-10018-8

Pandu Santhoju, Punit Bhalla, Laxmidhar Behera, R. Venketeswara Pai

{"title":"Mathematical model as per the algorithm of Sūryasiddhānta for computation of location specific true position of the planets","authors":"Pandu Santhoju, Punit Bhalla, Laxmidhar Behera, R. Venketeswara Pai","doi":"10.1007/s12036-024-10018-8","DOIUrl":"10.1007/s12036-024-10018-8","url":null,"abstract":"<div><p><i>Sūryasiddhānta</i> is an important astronomical treatise, which is very popular even now in the entire Indian sub-continent. Like other astronomical texts, <i>Sūryasiddhānta</i> describes the procedure to compute different astronomical parameters. However, the procedure to compute the planetary true positions for a given day (as per mid-night reckoning system) and place need to be applied independently for different planets. In this study, we are presenting a mathematical model for the computation of the true positions (<i>nirāyana</i> longitudes) of the planets at any given instant of time of the day for any desired place. This mathematical model is based on the algorithm presented in the <i>Sūryasiddhānta</i> with some modifications such as the usage of the fractional part of the <i>ahargaṇas</i>. The planetary positions or the longitudes of the planets are computed for the Sunrise of Mandi, Himachal Pradesh, and are compared with the Stellarium values (<i>nirāyana</i> – <i>Nirāyana</i> longitude values are obtained by applying the Precision of Equinox correction to the Stellarium Ecliptic (<i>sāyana</i>) longitudes.) to study the accuracy of the results obtained from the mathematical model.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142939050","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}

引用次数: 0

On the simultaneity of Forbush decreases: The simultaneous effects of interplanetary parameters and geomagnetic activity indices 关于Forbush的同时性衰减：行星际参数和地磁活动指数的同时效应

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-08 DOI: 10.1007/s12036-024-10028-6

I. O. Eya, E. U. Iyida, O. Okike, R. E. Ugwoke, F. M. Menteso, C. J. Ugwu, P. Simpemba, J. Simfukwe, D. Silungwe, S. P. Phiri, G. F. Abbey, J. A. Alhassan, A. E. Chukwude

{"title":"On the simultaneity of Forbush decreases: The simultaneous effects of interplanetary parameters and geomagnetic activity indices","authors":"I. O. Eya, E. U. Iyida, O. Okike, R. E. Ugwoke, F. M. Menteso, C. J. Ugwu, P. Simpemba, J. Simfukwe, D. Silungwe, S. P. Phiri, G. F. Abbey, J. A. Alhassan, A. E. Chukwude","doi":"10.1007/s12036-024-10028-6","DOIUrl":"10.1007/s12036-024-10028-6","url":null,"abstract":"<div><p>Forbush decreases (Fd) are transient, short-term reductions in the intensity of galactic cosmic rays that reach the Earth’s surface. When this reduction is observed at multiple locations simultaneously, it is referred to as simultaneous Forbush decreases (SFd). Identifying Fd events in daily averaged cosmic ray (CR) raw data is always tedious, but the task has gone minimal through an algorithm (automated Fd detection). We deployed an automated Fd location algorithm on daily-averaged CR data from five neutron monitor stations covering 1998–2006. We identified 80 days with the most simultaneous events. While there exists extensive research on the subject using a case study approach, the current study is statistical. Whereas most of the previous investigations employed a small sample of Fds manually selected from a single CR station, large samples of Fds selected after disentangling the Sun’s influence on CR data from multiple neutron monitors (NMs) are used. The connection between the Fds and many solar-terrestrial variables is tested. The beautiful and consistent results obtained between the space weather variables and Fds at the five NM stations call the attention of space weather researchers to the need for rigorous, detailed, and accurate cataloging of Fds. Solar cycle oscillation significantly impacts the amplitude and timing of Fds. Its influence should be removed before Fd selection.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142938852","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}

引用次数: 0

A method for identification of restarted radio sources from large radio surveys 一种从大型无线电调查中识别重新启动的射电源的方法

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2025-01-04 DOI: 10.1007/s12036-024-10035-7

Aparna Raj, C. H. Ishwara-Chandra, T. P. Sudheesh, K. G. Biju, Joe Jacob

{"title":"A method for identification of restarted radio sources from large radio surveys","authors":"Aparna Raj, C. H. Ishwara-Chandra, T. P. Sudheesh, K. G. Biju, Joe Jacob","doi":"10.1007/s12036-024-10035-7","DOIUrl":"10.1007/s12036-024-10035-7","url":null,"abstract":"<div><p>Active galaxies hosting radio jets can exhibit distinct active phases marked by two sets of radio lobes. Typically, these episodic radio sources have been identified through morphological observations. In addition, spectral characteristics-based methods are also employed wherever multi-frequency deep radio observations are available. However, these methods are inefficient in detecting restarted radio sources that do not exhibit a clear morphology. To address this, a method of using the spectral curvature (<span>({{textrm{SPC}}} = alpha ^{1400~{textrm{MHz}}} _{150~{textrm{MHz}}}-alpha ^{150~{textrm{MHz}}} _{74~{textrm{MHz}}})</span>) to identify restarted radio sources is presented. This is based on the fact that restarted radio sources with significant remnant emission are expected to have concave spectra in contrast to the convex or straight spectra observed in most radio sources. We use available wide area radio surveys in the range of frequencies from 74 MHz to 1.4 GHz to search for episodic radio sources and to shortlist 9,405 sources based on the criteria of <span>({textrm{SPC}} ge 0.5 )</span>. The candidates thus identified can be followed up for detailed morphological and spectral index studies. This method will find application in the automated identification of episodic radio sources in large radio sky surveys from telescopes like LOFAR and SKA.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142925591","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}

引用次数: 0

Gravitational physics in the context of Indian astronomy: A vision document 印度天文学背景下的引力物理学：远景文件

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-12-30 DOI: 10.1007/s12036-024-10031-x

P. Ajith, K. G. Arun, Sukanta Bose, Sumanta Chakraborty, Shantanu Desai, A. Gopakumar, Sanved Kolekar, Rajesh Nayak, Archana Pai, Sudipta Sarkar, Jasjeet Singh Bagla, Patrick Das Gupta, Rahul Kashyap, Prashant Kocherlakota, Prayush Kumar, Banibrata Mukhopadhyay

引用次数: 0

Development of a machine learning-based radio source localization algorithm for tri-axial antenna configuration 三轴天线配置中基于机器学习的射电源定位算法的开发

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-12-28 DOI: 10.1007/s12036-024-10032-w

Harsha Avinash Tanti, Abhirup Datta, Tiasha Biswas, Anshuman Tripathi

{"title":"Development of a machine learning-based radio source localization algorithm for tri-axial antenna configuration","authors":"Harsha Avinash Tanti, Abhirup Datta, Tiasha Biswas, Anshuman Tripathi","doi":"10.1007/s12036-024-10032-w","DOIUrl":"10.1007/s12036-024-10032-w","url":null,"abstract":"<div><p>Accurately determining the origin of radio emissions is essential for numerous scientific experiments, particularly in radio astronomy. Conventional techniques, such as antenna arrays, encounter significant challenges, especially at very low frequencies, due to factors like the substantial size of the antennas and ionospheric interference. To address these challenges, we employ a space-based single-telescope that utilizes co-located antennas complemented by goniopolarimetric techniques for precise source localization. This study explores a novel and elementary machine learning technique to improve and estimate direction of arrival (DoA), leveraging a tri-axial antenna arrangement for radio source localization. Employing a simplistic emission and receiving antenna model, our study involves training an artificial neural network (ANN) using synthetic radio signals. These synthetic signals can originate from any location in the sky and cover an incoherent frequency range of 0.3–30 MHz, with a signal-to-noise ratio between 0 and 60 dB. A large synthetic data set was generated to train the ANN model catering to the possible signal configurations and variations. After training, the developed ANN model demonstrated exceptional performance, achieving loss levels in the training (<span>({sim }0.02)</span>), validation (<span>({sim }0.23%)</span>), and testing (<span>({sim }0.21%)</span>) phases. The machine learning-based approach, remarkably, exhibits substantially quicker inference times (<span>({sim }5)</span> ms) in contrast to analytically derived DoA methods, which typically range from 100 ms to a few seconds. This underscores its practicality for real-time applications in radio source localization, particularly in scenarios with a limited number of sensors.</p></div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"46 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889857","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}

引用次数: 0

Bhūpajñādivākyas: A quick tool to extract the longitude of the Sun Bhūpajñādivākyas：一个快速提取太阳经度的工具

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-12-24 DOI: 10.1007/s12036-024-10016-w

R. Venketeswara Pai

引用次数: 0