Journal of Astrophysics and Astronomy最新文献_第7页

Turbulence and magnetic fields in star formation 恒星形成过程中的湍流和磁场

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-06-04 DOI: 10.1007/s12036-024-10005-z

Archana Soam, Chakali Eswaraiah, Amit Seta, Lokesh Dewangan, G. Maheswar

{"title":"Turbulence and magnetic fields in star formation","authors":"Archana Soam, Chakali Eswaraiah, Amit Seta, Lokesh Dewangan, G. Maheswar","doi":"10.1007/s12036-024-10005-z","DOIUrl":"10.1007/s12036-024-10005-z","url":null,"abstract":"<div>Molecular clouds are prime locations to study the process of star formation. These clouds contain filamentary structures and cores, which are crucial sites for the formation of young stars. The star-formation process has been investigated using various techniques, including polarimetry, for tracing magnetic fields. In this small review-cum-short report, we put together the efforts (mainly from the Indian community) to understand the roles of turbulence and magnetic fields in star formation. These are two components of the ISM competing against gravity, which is primarily responsible for the collapse of gas to form stars. We also include attempts made using simulations of molecular clouds to study this competition. Studies on feedback and magnetic fields are combined and listed to understand the importance of the interaction between two energies in setting the current observed star formation efficiency. We have listed available and upcoming facilities with the polarization capabilities needed to trace magnetic fields. We have also stated the importance of ongoing and desired collaborations between Indian communities and facilities abroad to shed more light on the roles of turbulence and magnetic fields in the process of star formation.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141253844","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

SolarAccel: FPGA accelerated 2D cross-correlation of digital images: Application to solar adaptive optics SolarAccel：FPGA 加速数字图像的二维交叉相关：应用于太阳能自适应光学

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-23 DOI: 10.1007/s12036-024-10003-1

Soham Das, Nanditha Rao, D. V. S. Phanindra, Sridharan Rengaswamy

{"title":"SolarAccel: FPGA accelerated 2D cross-correlation of digital images: Application to solar adaptive optics","authors":"Soham Das, Nanditha Rao, D. V. S. Phanindra, Sridharan Rengaswamy","doi":"10.1007/s12036-024-10003-1","DOIUrl":"10.1007/s12036-024-10003-1","url":null,"abstract":"<div>The cross-correlation of two-dimensional digital images is fundamental to solar adaptive optics computations. It can be used in a simple tip-tilt correction system to identify the relative shift between consecutive images and correlating sub-aperture images of a Shack–Hartmann wave-front sensor. The typical frequency of computation is about 1 kHz. While the software-based optimized cross-correlations may be sufficient when a small number of sub-apertures are used in a wave-front sensor, hardware-accelerated (FPGA), correlations may be required when a large number of sub-aperture images are involved, e.g., in the case of the proposed National Large Solar Telescope in India. This paper presents SolarAccel: An FPGA-based acceleration of a basic two-dimensional cross-correlation of two images. We accelerate the FPGA-based design by pipelining the individual components of the cross-correlation process. We implemented our RTL logic on a few sets of (128times 128) pixel images and (32times 32) pixel images on a Xilinx Zynq Ultrascale(+) MPSoC on the ZCU104 FPGA evaluation platform. SolarAccel performs a 2D FFT on a (128times 128) image faster than existing work. The cross-correlation on a (32times 32) image is also faster than the existing work. This demonstrates that FPGA acceleration is beneficial in solar adaptive optics applications.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141106711","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

Searching for wide binary stars with non-coeval components in the northern sky 在北部天空寻找具有非同步成分的宽双星

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-13 DOI: 10.1007/s12036-024-10002-2

Oleg Malkov, Alexey Kniazev, Stanislav Gorda

引用次数: 0

Extreme value theory applied to long-term sunspot areas 应用于长期太阳黑子区域的极值理论

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-05-03 DOI: 10.1007/s12036-024-09999-3

Rui Zhang, Yan-Qing Chen, Shu-Guang Zeng, Sheng Zheng, Yan-Shan Xiao, Lin-Hua Deng, Xiang-Yun Zeng, Yao Huang

{"title":"Extreme value theory applied to long-term sunspot areas","authors":"Rui Zhang, Yan-Qing Chen, Shu-Guang Zeng, Sheng Zheng, Yan-Shan Xiao, Lin-Hua Deng, Xiang-Yun Zeng, Yao Huang","doi":"10.1007/s12036-024-09999-3","DOIUrl":"10.1007/s12036-024-09999-3","url":null,"abstract":"<div>Solar activity, such as sunspots and flares, has a great impact on humans, living beings, and technologies in the whole world. Changes in sunspots will influence high-frequency and space-navigation radio communications. Based on the full-disk, southern and northern hemispheres sunspot areas (SAs) data in 1874–2023 from the Royal Observatory, Greenwich (RGO) USAF/NOAA, extreme value theory (EVT) is applied to predict the trend of the 25th and 26th solar cycles (SCs) in this work. Two methods with EVT, the block maxima (BM) approach and the peaks-over-threshold (POT) approach, are employed to research solar extreme events. The former method focuses on each block’s maximum sunspot areas value and is applied for the generalized extreme value (GEV) distribution. The latter method aims to select the extreme values exceeding a threshold value and is used to obtain the generalized Pareto (GP) distribution. It is the first time that the EVT is applied on the sunspot areas data from the Royal Observatory, Greenwich (RGO) USAF/NOAA. The analysis indicates that the estimated 8-year return levels for sunspot areas are 5701 and 6258 using the two methods, while the estimated 19-year return levels are all 7165. This suggests that the trends of the 25th and 26th solar cycles will be stronger than that of the 24th solar cycle.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140883753","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

Study of magnetic field evolution by Weibel instability in counter-streaming electron–positron plasma flows 逆流电子-正电子等离子体流中魏伯尔不稳定性引起的磁场演化研究

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-04-02 DOI: 10.1007/s12036-024-10001-3

Rakesh Kumar, Hitendra K. Malik, Sandeep Kumar

{"title":"Study of magnetic field evolution by Weibel instability in counter-streaming electron–positron plasma flows","authors":"Rakesh Kumar, Hitendra K. Malik, Sandeep Kumar","doi":"10.1007/s12036-024-10001-3","DOIUrl":"10.1007/s12036-024-10001-3","url":null,"abstract":"<div>Collisionless shocks are generated via the magnetic field mediated by Weibel instability in astrophysical systems. In this work, by performing particle-in-cell (PIC) simulations, Weibel instability-mediated magnetic field amplification is investigated for initially unmagnetized, spatially uniform, counter-streaming electron–positron (e−/e+) plasma flows and compared with the magnetic amplification for nonuniform counter-streaming e−/e+ plasma flows by considering their drift velocity of (0.5 c). Our simulation results show that initially, the magnetic field grows exponentially in the linear regime and then decays further after saturation for homogeneous e−/e+ plasma flows. However, in the case of inhomogeneous counter-streaming e−/e+ plasma flow, the magnetic field re-amplifies in the post-saturation region after the first saturation. It is found that the amplification magnitude of magnetic field energy in the post-saturation region is related to the density fluctuations for upstream plasma. Our calculations show that temperature anisotropy is the reason behind the second saturation of the magnetic field energy in the case of inhomogeneous plasma distribution. Such inhomogeneous media in astrophysical systems like Gamma-ray bursts are common. Therefore, this study will be useful for understanding collisionless shocks' formation and their effects.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140580620","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

In-situ acceleration of radio-emitting particles in the lobes of radio galaxies: Evolving observational perspective and recent clues 射电星系裂片中射电发射粒子的原位加速：不断发展的观测视角和最新线索

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-04-01 DOI: 10.1007/s12036-024-10000-4

Gopal-Krishna, Paul J. Wiita

引用次数: 0

Long-term spectroscopic monitoring of comet 46P/Wirtanen 对 46P/Wirtanen 彗星的长期光谱监测

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-03-16 DOI: 10.1007/s12036-024-09996-6

K. Aravind, Kumar Venkataramani, Shashikiran Ganesh, Emmanuel Jehin, Youssef Moulane

{"title":"Long-term spectroscopic monitoring of comet 46P/Wirtanen","authors":"K. Aravind, Kumar Venkataramani, Shashikiran Ganesh, Emmanuel Jehin, Youssef Moulane","doi":"10.1007/s12036-024-09996-6","DOIUrl":"10.1007/s12036-024-09996-6","url":null,"abstract":"<div>Jupiter family comets, having an orbital period <20 years, allow us to observe their activity and analyze the homogeneity in their coma composition over multiple apparitions. Comet 46P/Wirtanen, with its exceptionally close approach to Earth during its 2018 apparition, offered the possibility for long-term spectroscopic observations. We used a 1.2 m telescope equipped with a low-resolution spectrograph to monitor the comet’s activity and compute the relative abundances in the coma as a function of heliocentric distance. We report the production rates of four molecules CN, C(_2), C(_3) and NH(_2,) and Af(rho ) parameter, a proxy to the dust production, before and after perihelion. We found that 46P has a typical coma composition with almost constant abundance ratios with respect to CN across the epochs of observation. Comparing the coma composition of comet 46P during the current and previous apparitions, we conclude the comet has a highly homogeneous chemical composition in the nucleus with an enhancement in ammonia abundance compared to the average abundance in comets.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140151399","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

Detection of continuum emission and atomic hydrogen from comet C/2020 F3 NEOWISE using GMRT 利用全球红外辐射计探测C/2020 F3 NEOWISE彗星的连续发射和原子氢

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-03-14 DOI: 10.1007/s12036-024-09998-4

Sabyasachi Pal, Arijit Manna

{"title":"Detection of continuum emission and atomic hydrogen from comet C/2020 F3 NEOWISE using GMRT","authors":"Sabyasachi Pal, Arijit Manna","doi":"10.1007/s12036-024-09998-4","DOIUrl":"10.1007/s12036-024-09998-4","url":null,"abstract":"<div>Comets are the most primordial objects in our solar system. Comets are icy bodies that release gas and dust when moving close to the Sun. The C/2020 F3 (Near-Earth Object Wide-field Infrared Survey Explorer: NEOWISE) is a nearly isotropic comet moving near-parabolic orbit. The C/2020 F3 (NEOWISE) was the brightest comet in the northern hemisphere after comet Hale–Bopp in 1997 and comet McNaught in 2006. This paper presents the first interferometric high-resolution detection of the comet C/2020 F3 (NEOWISE) using the Giant Metrewave Radio Telescope (GMRT). We detected the radio continuum emission from the comet C/2020 F3 (NEOWISE) with a flux density level 2.84 (±0.56)–3.89 (±0.57) mJy in the frequency range of 1050–1450 MHz. We also detected the absorption line of atomic hydrogen (HI) with a signal-to-noise ratio (SNR) (sim )5.7. The column density of the detected HI absorption line is (N_{textrm{HI}} = (3.46pm 0.60)times (T_{s}/100)times 10^{21},hbox {cm}^{-2}), where we assume the spin temperature (T_{s} = 100) K and filling factor (f = 1). The significant detection of continuum emission from the comet C/2020 F3 (NEOWISE) at (sim )21 cm wavelength indicated that it arose from the large icy grains halo (IGH) region.</div>","PeriodicalId":610,"journal":{"name":"Journal of Astrophysics and Astronomy","volume":"45 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140151542","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

Markov Chain Monte Carlo optimization applied to double stars from Miller & Pitman research 将马尔可夫链蒙特卡洛优化技术应用于米勒和皮特曼研究的双星

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-03-05 DOI: 10.1007/s12036-024-09997-5

Maksym Ersteniuk, Timothy Banks, Edwin Budding, Michael D. Rhodes

引用次数: 0

Optical design studies for national large optical-IR telescope 国家大型光学-红外望远镜光学设计研究

IF 1.1 4区物理与天体物理

Journal of Astrophysics and Astronomy Pub Date : 2024-02-29 DOI: 10.1007/s12036-024-09995-7

Varun Padikal, Amirul Hasan, Vineeth Valsan, S. Sriram, Athul Kurian, Vishnu C. Unni, Alikhan Basheer, Pramod Panchal, Maheswar Gopinathan, B. S. Remya, Totan Chand

引用次数: 0