Pub Date : 2024-05-23DOI: 10.1088/1674-4527/ad4fc4
Yazhou Zhang, hailong zhang, Jie WANG, Jian Li, Xinchen YE, ShuangQiang Wang, Xu Du, Han Wu, Ting ZHANG, Shao-Cong Guo
For real-time processing of ultra-wide bandwidth low-frequency pulsar base band data, we designed and implemented an ultra-wide bandwidth pulsar data processing pipeline(UWLPIPE) based on the shared ringbuffer and GPU parallel technology. UWLPIPE runs on the GPU cluster and can simultaneously receive multiple 128 MHz dual-polarization VDIF data packets preprocessed by the front-end FPGA. After aligning the dual-polarization data, multiple 128M subband data are packaged into PSRDADA baseband data or multi channel coherent dispersion filterbank data, and multiple subband filterbank data can be spliced into wideband data after time alignment. We used the Nanshan 26-meter radio telescope with L-band receiver at 964-1732 MHz to observe multiple pulsars. Finally, we processed the data using DSPSR software, and the results showed that each subband could correctly fold out the pulse profile, and the wideband pulse profile accumulated by multiple subbands could be correctly aligned.
{"title":"UWLPIPE: Ultra-Wide Bandwidth Pulsar Data Processing Pipeline","authors":"Yazhou Zhang, hailong zhang, Jie WANG, Jian Li, Xinchen YE, ShuangQiang Wang, Xu Du, Han Wu, Ting ZHANG, Shao-Cong Guo","doi":"10.1088/1674-4527/ad4fc4","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4fc4","url":null,"abstract":"\u0000 For real-time processing of ultra-wide bandwidth low-frequency pulsar base band data, we designed and implemented an ultra-wide bandwidth pulsar data processing pipeline(UWLPIPE) based on the shared ringbuffer and GPU parallel technology. UWLPIPE runs on the GPU cluster and can simultaneously receive multiple 128 MHz dual-polarization VDIF data packets preprocessed by the front-end FPGA. After aligning the dual-polarization data, multiple 128M subband data are packaged into PSRDADA baseband data or multi channel coherent dispersion filterbank data, and multiple subband filterbank data can be spliced into wideband data after time alignment. We used the Nanshan 26-meter radio telescope with L-band receiver at 964-1732 MHz to observe multiple pulsars. Finally, we processed the data using DSPSR software, and the results showed that each subband could correctly fold out the pulse profile, and the wideband pulse profile accumulated by multiple subbands could be correctly aligned.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"20 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141107812","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-22DOI: 10.1088/1674-4527/ad4f25
Weidan Zhang, Bing Wang, Zhao Wu, Guang Lu, Yao Chen, Fa-bao Yan
The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun. The image acquired by the telescope results from convoluting the Sun’s true brightness distribution with the antenna array’s directional pattern. The imaging quality of the radioheliograph is affected by a multitude of factors, with the performance of the ” dirty beam” being just one component. Other factors such as imaging methods, calibration techniques, clean algorithms, and more also play a significant influence on the resulting image quality. As the layout of the antenna array directly affects the performance of the dirty beam, the design of an appropriate antenna configuration is critical to improving the imaging quality of the radioheliograph. Based on the actual needs of observing the Sun, this work optimized the antenna array design and proposed a two-dimensional low-redundancy array. The proposed array was compared with common T shaped arrays, Y-shaped arrays, uniformly spaced circular arrays, and three-arm spiral arrays. Through simulations and experiments, their performance in terms of sampling point numbers, UV coverage area, beam-half width, sidelobe level, and performance in the absence of antennas are compared and analyzed. It was found that each of these arrays has its advantages, but the two-dimensional low-redundancy array proposed in this paper performs best in overall evaluation. It has the shortest imaging calculation time among the array types and is highly robust when antennas are missing, making it the most suitable choice.
射电日像仪是一个庞大的天线阵列，利用孔径合成原理产生太阳图像。望远镜获得的图像是将太阳的真实亮度分布与天线阵列的方向性模式相合成的结果。射电日像仪的成像质量受到多种因素的影响，"脏光束 "的性能只是其中一个因素。成像方法、校准技术、清洁算法等其他因素也会对成像质量产生重要影响。由于天线阵列的布局直接影响脏波束的性能，因此设计合适的天线配置对于提高射电日像仪的成像质量至关重要。根据观测太阳的实际需要，这项工作优化了天线阵列设计，提出了一种二维低冗余阵列。将所提出的阵列与常见的 T 形阵列、Y 形阵列、均匀间隔圆形阵列和三臂螺旋阵列进行了比较。通过模拟和实验，比较和分析了它们在采样点数、紫外覆盖面积、波束半宽、边幅水平以及无天线情况下的性能。结果发现，这些阵列各有优势，但本文提出的二维低冗余阵列在总体评价中表现最佳。在所有阵列类型中，它的成像计算时间最短，而且在天线缺失时具有很强的鲁棒性，因此是最合适的选择。
{"title":"A Novel Two-dimensional Low-redundancy Array Design for Solar Radio Imaging","authors":"Weidan Zhang, Bing Wang, Zhao Wu, Guang Lu, Yao Chen, Fa-bao Yan","doi":"10.1088/1674-4527/ad4f25","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4f25","url":null,"abstract":"\u0000 The radioheliograph is an extensive array of antennas operating on the principle of aperture synthesis to produce images of the Sun. The image acquired by the telescope results from convoluting the Sun’s true brightness distribution with the antenna array’s directional pattern. The imaging quality of the radioheliograph is affected by a multitude of factors, with the performance of the ” dirty beam” being just one component. Other factors such as imaging methods, calibration techniques, clean algorithms, and more also play a significant influence on the resulting image quality. As the layout of the antenna array directly affects the performance of the dirty beam, the design of an appropriate antenna configuration is critical to improving the imaging quality of the radioheliograph. Based on the actual needs of observing the Sun, this work optimized the antenna array design and proposed a two-dimensional low-redundancy array. The proposed array was compared with common T shaped arrays, Y-shaped arrays, uniformly spaced circular arrays, and three-arm spiral arrays. Through simulations and experiments, their performance in terms of sampling point numbers, UV coverage area, beam-half width, sidelobe level, and performance in the absence of antennas are compared and analyzed. It was found that each of these arrays has its advantages, but the two-dimensional low-redundancy array proposed in this paper performs best in overall evaluation. It has the shortest imaging calculation time among the array types and is highly robust when antennas are missing, making it the most suitable choice.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"44 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141112339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Chinese Space Station Telescope (CSST) is a telescope with 2-meter diameter, obtaining images with high quality through wide-field observations. In its first observation cycle, the CSST will scan portions of the galactic centre with 7 different bands across different epochs to capture time-domain observation data. These data have significant potential for the study of properties of stars and exoplanets. However, the density of stars in the galactic centre is high, and it is a well-known challenge to perform astrometry and photometry in such a dense star field. This paper presents a deep learning-based framework designed to process dense star field images obtained by the CSST, which includes photometry, astrometry, and classifications of targets according to their light curve periods. With simulated CSST observation data, we demonstrate that this deep learning framework achieves photometry accuracy of 0.23% and astrometry accuracy of 0.03 pixel for stars with moderate brightness mag=24 in i band, surpassing results obtained by traditional methods. Additionally, the deep learning based light curve classification algorithm could pick up celestial targets whose magnitude variations are 1.7 times larger than magnitude variations brought by Poisson Photon Noise. We anticipate that our framework could be effectively used to process dense star field images obtained by the CSST.
{"title":"CSST Dense Star Field Preparation: A Framework for Astrometry and Photometry for Dense Star Field Images Obtained by the China Space Station Telescope (CSST)","authors":"Yining Wang, Rui Sun, Tianyuan Deng, Chenghui Zhao, Peixuan Zhao, Jiayi Yang, Peng Jia, Hui-Gen Liu, Jilin Zhou","doi":"10.1088/1674-4527/ad4df5","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4df5","url":null,"abstract":"\u0000 The Chinese Space Station Telescope (CSST) is a telescope with 2-meter diameter, obtaining images with high quality through wide-field observations. In its first observation cycle, the CSST will scan portions of the galactic centre with 7 different bands across different epochs to capture time-domain observation data. These data have significant potential for the study of properties of stars and exoplanets. However, the density of stars in the galactic centre is high, and it is a well-known challenge to perform astrometry and photometry in such a dense star field. This paper presents a deep learning-based framework designed to process dense star field images obtained by the CSST, which includes photometry, astrometry, and classifications of targets according to their light curve periods. With simulated CSST observation data, we demonstrate that this deep learning framework achieves photometry accuracy of 0.23% and astrometry accuracy of 0.03 pixel for stars with moderate brightness mag=24 in i band, surpassing results obtained by traditional methods. Additionally, the deep learning based light curve classification algorithm could pick up celestial targets whose magnitude variations are 1.7 times larger than magnitude variations brought by Poisson Photon Noise. We anticipate that our framework could be effectively used to process dense star field images obtained by the CSST.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"86 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141122865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-17DOI: 10.1088/1674-4527/ad4d3b
Valeria Kostiuk, Alexander Marchuk, Alexander Gusev
A co-rotation radius is a key characteristic of disc galaxies that is essential to determine the angular speed of the spiral structure Ωp, and therefore understand its nature. In the literature, there are plenty of methods to estimate this value, but do these measurements have any consistency? In this work, we collected a dataset of corotation radius measurements for 547 galaxies, 300 of which had at least two values. An initial analysis reveals that most objects have rather inconsistent corotation radius positions. Moreover, a significant fraction of galactic discs is distinguished by a large error coverage and almost uniform distribution of measurements. These findings do not have any relation to spiral type, Hubble classification, or presence of a bar. Among other reasons, obtained results could be explained by the transient nature of spirals in a considerable part of galaxies. We have made our collected data sample publicly available, and have demonstrated on one example how it could be useful for future research by investigating a winding time value for a sample of galaxies with possible multiple spiral arm patterns.
{"title":"Cross-method analysis of co-rotation radii dataset for spiral galaxies","authors":"Valeria Kostiuk, Alexander Marchuk, Alexander Gusev","doi":"10.1088/1674-4527/ad4d3b","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4d3b","url":null,"abstract":"\u0000 A co-rotation radius is a key characteristic of disc galaxies that is essential to determine the angular speed of the spiral structure Ωp, and therefore understand its nature. In the literature, there are plenty of methods to estimate this value, but do these measurements have any consistency? In this work, we collected a dataset of corotation radius measurements for 547 galaxies, 300 of which had at least two values. An initial analysis reveals that most objects have rather inconsistent corotation radius positions. Moreover, a significant fraction of galactic discs is distinguished by a large error coverage and almost uniform distribution of measurements. These findings do not have any relation to spiral type, Hubble classification, or presence of a bar. Among other reasons, obtained results could be explained by the transient nature of spirals in a considerable part of galaxies. We have made our collected data sample publicly available, and have demonstrated on one example how it could be useful for future research by investigating a winding time value for a sample of galaxies with possible multiple spiral arm patterns.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"1 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140962887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
After launching a jet, outflows of magnetar were used to account for the achromatic plateau of afterglow and the early X-ray flux plateau known as "internal plateau''. The lack of detecting magnetic dipole emission together with the energy injection feature in a single observation poses confusion until the long gamma-ray burst (GRB) 210610B is detected. GRB 210610B is presented with an optical bump following an early X-ray plateau during the afterglow phase. The plateau followed by a steep decline flux overlays in the steadily decaying X-ray flux with index α X,1 ∼ 2.06, indicating an internal origin and that can be fitted by the spin-down luminosity law with the initial plateau luminosity log10 L X ∼ 48.29 erg s-1 and the characteristic spin-down timescale T ∼ 2818 s. A subsequent bump begins at ∼ 4000 s in R band with a rising index α R,1 ∼ -0.30 and peaks at ∼ 14125 s, after which a decay index α R,2 ∼ 0.87 and finally transiting to a steep decay with α R,3 ∼ 1.77 achieve the closure relation of the external shock for the normal decay phase as well as the magnetar spin-down energy injection phase, provided that the average value of the photon index Γγ = 1.80 derived from the spectral energy distributions (SEDs) between the X-ray and optical afterglow. The closure relation also works for the late X-ray flux. Akin to the traditional picture of GRB, the outflow powers the early X-ray plateau by dissipating energy internally and collides with the leading decelerating blast burst as time goes on, which could interpret the exotic feature of GRB 210610B. We carry out a Markov Chain Monte Carlo (MCMC) simulation and obtain a set of best parameters: ε B ≈ 4.2 × 10-5, ε e ≈ 0.16, E K,iso ≈ 4.2× 1053 ergs, Γ0 ≈ 851, A* ≈ 0.11, L inj,0 ≈ 2.31 × 1050 erg s-1. The artificial light curve can fit the afterglow data well. After that, we estimated the average Lorentz factor and the X-ray radiation efficiency of the later ejecta are 35 and 0.13%, respectively.
在发射喷流之后，磁星的外流被用来解释余辉的消色高原和被称为 "内部高原 "的早期 X 射线通量高原。在探测到长伽马射线暴（GRB）210610B 之前，由于在一次观测中没有探测到磁偶极子发射和能量注入特征，因此造成了混淆。GRB 210610B 在余辉阶段的早期 X 射线高原之后出现了一个光学凸起。高原之后的通量急剧下降，与指数 α X,1 ∼ 2.06 的稳定衰减 X 射线通量重叠，表明其内部起源，可以用自旋下降光度定律来拟合，初始高原光度 log10 L X ∼ 48.随后在 R 波段从 ∼ 4000 秒开始出现凸起，指数 α R,1 ∼ -0.之后衰变指数α R,2 ∼ 0.87，最后过渡到α R,3 ∼ 1.77的陡峭衰变，从而实现了正常衰变阶段以及磁星自旋下降能量注入阶段的外部冲击闭合关系，条件是根据X射线和光学余辉之间的光谱能量分布（SED）得出的光子指数Γγ = 1.80的平均值。闭合关系也适用于晚期 X 射线通量。与GRB的传统图景相似，流出物通过内部耗散能量为早期X射线高原提供能量，并随着时间的推移与前导减速爆炸爆发相撞，这可以解释GRB 210610B的奇异特征。我们进行了马尔可夫链蒙特卡罗（MCMC）模拟，得到了一组最佳参数：ε B ≈ 4.2 × 10-5，ε e ≈ 0.16，E K,iso ≈ 4.2× 1053 ergs，Γ0 ≈ 851，A* ≈ 0.11，L inj,0 ≈ 2.31 × 1050 erg s-1。人工光曲线可以很好地拟合余辉数据。之后，我们估算出后期喷出物的平均洛伦兹因子和 X 射线辐射效率分别为 35% 和 0.13%。
{"title":"GRB 210610B: The Internal and External Plateau As Evidence For The Delayed Outflow Of Magnetar","authors":"Yining Wei, Xianggao Wang, Da-Bin Lin, Weikang Zheng, Liang-Jun Chen, Sheng-Yu Yan, Shuangxi Yi, Qi Wang, ZI-Min Zhou, Hui-Ya Liu, En-Wei Liang","doi":"10.1088/1674-4527/ad4d3a","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4d3a","url":null,"abstract":"\u0000 After launching a jet, outflows of magnetar were used to account for the achromatic plateau of afterglow and the early X-ray flux plateau known as \"internal plateau''. The lack of detecting magnetic dipole emission together with the energy injection feature in a single observation poses confusion until the long gamma-ray burst (GRB) 210610B is detected. GRB 210610B is presented with an optical bump following an early X-ray plateau during the afterglow phase. The plateau followed by a steep decline flux overlays in the steadily decaying X-ray flux with index α\u0000 X,1 ∼ 2.06, indicating an internal origin and that can be fitted by the spin-down luminosity law with the initial plateau luminosity log10\u0000 L\u0000 X ∼ 48.29 erg s-1 and the characteristic spin-down timescale T ∼ 2818 s. A subsequent bump begins at ∼ 4000 s in R band with a rising index α\u0000 R,1 ∼ -0.30 and peaks at ∼ 14125 s, after which a decay index α\u0000 R,2 ∼ 0.87 and finally transiting to a steep decay with α\u0000 R,3 ∼ 1.77 achieve the closure relation of the external shock for the normal decay phase as well as the magnetar spin-down energy injection phase, provided that the average value of the photon index Γγ = 1.80 derived from the spectral energy distributions (SEDs) between the X-ray and optical afterglow. The closure relation also works for the late X-ray flux. Akin to the traditional picture of GRB, the outflow powers the early X-ray plateau by dissipating energy internally and collides with the leading decelerating blast burst as time goes on, which could interpret the exotic feature of GRB 210610B. We carry out a Markov Chain Monte Carlo (MCMC) simulation and obtain a set of best parameters: ε\u0000 B\u0000 \u0000 ≈ 4.2 × 10-5, ε\u0000 e\u0000 \u0000 ≈ 0.16, E\u0000 K,iso ≈ 4.2× 1053 ergs, Γ0 ≈ 851, A* ≈ 0.11, L\u0000 inj,0 ≈ 2.31 × 1050 erg s-1. The artificial light curve can fit the afterglow data well. After that, we estimated the average Lorentz factor and the X-ray radiation efficiency of the later ejecta are 35 and 0.13%, respectively.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"62 17","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140964707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-09DOI: 10.1088/1674-4527/ad4962
Akhila K, Ranjeev Misra, Savithri H. Ezhikode, Jeena K.
We present the results from a long term X-ray analysis of Mrk 279 during the period 2018-2020. We use data from multiple missions - AstroSat, NuSTAR and XMM-Newton, for the purpose. TheX-ray spectrum can be modelled as a double Comptonisation along with the presence of neutral Fe Kα line emission, at all epochs. We determined the source’s X-ray flux and luminosity at these different epochs. We find significant variations in the source’s flux state. We also investigated the variations in the source’s spectral components during the observation period. We find that the photon index and hence the spectral shape follow the variations only over longer time periods. We probe the correlations between fluxes of different bands and their photon indices, and found no significant correlations between the parameters.
我们将介绍 2018-2020 年期间对 Mrk 279 进行长期 X 射线分析的结果。为此，我们使用了来自 AstroSat、NuSTAR 和 XMM-Newton 等多个任务的数据。X射线光谱可以被模拟为双康普顿化，同时在所有时间段都存在中性铁Kα线发射。我们测定了该光源在这些不同时间段的 X 射线通量和光度。我们发现该源的通量状态变化很大。我们还研究了观测期间该源光谱成分的变化。我们发现光子指数以及光谱形状只在较长的时间段内才会发生变化。我们探究了不同波段的通量与其光子指数之间的相关性，发现参数之间没有明显的相关性。
{"title":"Long term X-ray spectral variations of the Seyfert-1 galaxy Mrk 279","authors":"Akhila K, Ranjeev Misra, Savithri H. Ezhikode, Jeena K.","doi":"10.1088/1674-4527/ad4962","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4962","url":null,"abstract":"\u0000 We present the results from a long term X-ray analysis of Mrk 279 during the period 2018-2020. We use data from multiple missions - AstroSat, NuSTAR and XMM-Newton, for the purpose. TheX-ray spectrum can be modelled as a double Comptonisation along with the presence of neutral Fe Kα line emission, at all epochs. We determined the source’s X-ray flux and luminosity at these different epochs. We find significant variations in the source’s flux state. We also investigated the variations in the source’s spectral components during the observation period. We find that the photon index and hence the spectral shape follow the variations only over longer time periods. We probe the correlations between fluxes of different bands and their photon indices, and found no significant correlations between the parameters.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":" 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140995051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-09DOI: 10.1088/1674-4527/ad4963
Y. Ban, Shang Shi, Na Wang, Qian Xu, Shufei Feng
Active surface technique is one of the key technologies to ensure the reflector accuracy of the millimeter/sub-millimeter wave large reflector antenna. The antenna is complex, large-scale, and high-precision equipment, and its active surfaces are affected by various factors that are difficult to comprehensively deal with. In this paper, based on the advantage of deep learning method that can be improved through data learning, we propose the active adjustment value analysis method of large reflector antenna based on deep learning. This method constructs a neural network model for antenna active adjustment analysis in view of the fact that a large reflector antenna consists of multiple panels spliced together. Based on the constraint that a single actuator has to support multiple panels (usually 4), an autonomously learned neural network emphasis layer module is designed to enhance the adaptability of the active adjustment neural network model. The classical 8-meter antenna is used as a case study, the actuators have an mean adjustment error of 0.00252 mm, and the corresponding antenna surface error is 0.00523 mm. This active adjustment result shows the effectiveness of the method in this paper.
{"title":"The Adjustment Analysis Method of the Active Surface Antenna Based on Convolutional Neural Network","authors":"Y. Ban, Shang Shi, Na Wang, Qian Xu, Shufei Feng","doi":"10.1088/1674-4527/ad4963","DOIUrl":"https://doi.org/10.1088/1674-4527/ad4963","url":null,"abstract":"\u0000 Active surface technique is one of the key technologies to ensure the reflector accuracy of the millimeter/sub-millimeter wave large reflector antenna. The antenna is complex, large-scale, and high-precision equipment, and its active surfaces are affected by various factors that are difficult to comprehensively deal with. In this paper, based on the advantage of deep learning method that can be improved through data learning, we propose the active adjustment value analysis method of large reflector antenna based on deep learning. This method constructs a neural network model for antenna active adjustment analysis in view of the fact that a large reflector antenna consists of multiple panels spliced together. Based on the constraint that a single actuator has to support multiple panels (usually 4), an autonomously learned neural network emphasis layer module is designed to enhance the adaptability of the active adjustment neural network model. The classical 8-meter antenna is used as a case study, the actuators have an mean adjustment error of 0.00252 mm, and the corresponding antenna surface error is 0.00523 mm. This active adjustment result shows the effectiveness of the method in this paper.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":" 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140994438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-07DOI: 10.1088/1674-4527/ad484f
Bing-Ru Wang, Di Li, P. Goldsmith, Jingwen Wu, Chao-Wei Tsai, R. Schieder, G. J. Melnick
The Submillimeter Wave Astronomy Satellite (SWAS) was the first space telescope capable of high spectral resolution observations of terahertz spectral lines. We have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit operation. The C I, O2, H2O and 13CO spectra taken towards all observed Galactic sources were analyzed. The present results are based on spectra with total integration time up to 2.72 × 104 hours (≃ 108 s). The noise in the spectra is shown to be generally consistent with that expected from the radiometer equation, without any sign of approaching a noise floor. This noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.
{"title":"Long-term Integration Ability of the Submillimeter Wave Astronomy Satellite (SWAS) Spectral Line Receivers","authors":"Bing-Ru Wang, Di Li, P. Goldsmith, Jingwen Wu, Chao-Wei Tsai, R. Schieder, G. J. Melnick","doi":"10.1088/1674-4527/ad484f","DOIUrl":"https://doi.org/10.1088/1674-4527/ad484f","url":null,"abstract":"\u0000 The Submillimeter Wave Astronomy Satellite (SWAS) was the first space telescope capable of high spectral resolution observations of terahertz spectral lines. We have investigated the integration ability of its two receivers and spectrometer during five and a half years of on-orbit operation. The C I, O2, H2O and 13CO spectra taken towards all observed Galactic sources were analyzed. The present results are based on spectra with total integration time up to 2.72 × 104 hours (≃ 108 s). The noise in the spectra is shown to be generally consistent with that expected from the radiometer equation, without any sign of approaching a noise floor. This noise performance reflects the extremely stable performance of the passively cooled front end as well as other relevant components in the SWAS instrument throughout its mission lifetime.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141002788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-07DOI: 10.1088/1674-4527/ad484e
Jianpeng Dai, Wei Han, Na Wang
The pulsar timing offers a comprehensive avenue for exploring diverse topics physics and astrophysics. High-precision solar system planetary ephemeris crucial for pulsar timing as it provides the positions and velocities of solar system planets include the Earth. However, it is inevitable that inherent inconsistencies exist in these ephemerides. Differences between various ephemerides can significantly impact pulsar timing and parameter estimations. Currently, pulsar timing highly depend on the JPL DE ephemeris, for instance, the Pulsar Timing Array (PTA) data analysis predominantly utilizes DE436. In this study, we examine inconsistencies across various ephemeris series, including JPL DE, EPM, and INPOP. Notably, discrepancies emerge particularly between the current ephemeris DE436 and the earliest released ephemeris DE200, as well as the most recent ephemerides, e.g. DE440, INPOP21A, and EPM2021. A further detailed analysis of the effects of ephemeris on geometric correction procedures for the conversion of measured topocentric Time of Arrivals (TOAs) is presented in this study. Our researches reveal that variations in the Roemer delays across different ephemerides lead to distinct differences. The timing residuals and the fact that these discrepancies can be readily incorporated into the subsequent pulsar parameters, leading to inconsistent fitting estimates, suggest that the influence of errors in the ephemeris on the timing process might currently be underappreciated.
{"title":"The Influence of Different Solar System Planetary Ephemeris on Pulsar Timing","authors":"Jianpeng Dai, Wei Han, Na Wang","doi":"10.1088/1674-4527/ad484e","DOIUrl":"https://doi.org/10.1088/1674-4527/ad484e","url":null,"abstract":"\u0000 The pulsar timing offers a comprehensive avenue for exploring diverse topics physics and astrophysics. High-precision solar system planetary ephemeris crucial for pulsar timing as it provides the positions and velocities of solar system planets include the Earth. However, it is inevitable that inherent inconsistencies exist in these ephemerides. Differences between various ephemerides can significantly impact pulsar timing and parameter estimations. Currently, pulsar timing highly depend on the JPL DE ephemeris, for instance, the Pulsar Timing Array (PTA) data analysis predominantly utilizes DE436. In this study, we examine inconsistencies across various ephemeris series, including JPL DE, EPM, and INPOP. Notably, discrepancies emerge particularly between the current ephemeris DE436 and the earliest released ephemeris DE200, as well as the most recent ephemerides, e.g. DE440, INPOP21A, and EPM2021. A further detailed analysis of the effects of ephemeris on geometric correction procedures for the conversion of measured topocentric Time of Arrivals (TOAs) is presented in this study. Our researches reveal that variations in the Roemer delays across different ephemerides lead to distinct differences. The timing residuals and the fact that these discrepancies can be readily incorporated into the subsequent pulsar parameters, leading to inconsistent fitting estimates, suggest that the influence of errors in the ephemeris on the timing process might currently be underappreciated.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"47 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141003426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.1088/1674-4527/ad47dd
Chaoyue Li, Linqiao Jiang, Jie Zheng, Yiman Liu, Xiaoyu Long, Min Sun, Hanlu Zhang, Xiao-man Tian
V0405 Dra is a W UMa-type binary star. Basing on the TESS data, we have conducted an orbital period study and performed a light curve analysis for the system. The orbital period study reveals that the $O-C$ curve for V0405 Dra exhibits secular decrease at an extremely high rate of $dP/dt = -2.71 times 10^{-6} daycdot year^{-1}$, along with periodic variations characterized by an amplitude of $A_3 = 0.0032$ days and a period of $P_3 = 1.413 $ years. The orbital periodic change is possibly due to the light-travel time effect resulting from an additional third body in the system, for which we estimate a minimum mass of $M_3 = 0.77 M_{odot}$. By employing the add{2013 version of the} Wilson-Devinney (W-D add{2013}) method to synthesize light curve, we derived photometric solutions indicating that V0405 Dra is a new deep ($f = 68.7%$)and low-mass ratio ($q =0.175$) contact binary. The fast decrease in its orbital period is likely caused by mass transfer from the more massive primary star to the less massive secondary star, or due to angular momentum loss, which have been elaborated upon in the last section. With further mass transfer and loss of angular momentum, the binary will gradually evolve into a tighter contact configuration, eventually leading to a merge into a single star, following the evolutionary paths suggested for such deep and low mass ratio contact binaries.
{"title":"V0405 Dra: a new deep and low mass ratio contact binary with extremely fast decrease in the orbital period","authors":"Chaoyue Li, Linqiao Jiang, Jie Zheng, Yiman Liu, Xiaoyu Long, Min Sun, Hanlu Zhang, Xiao-man Tian","doi":"10.1088/1674-4527/ad47dd","DOIUrl":"https://doi.org/10.1088/1674-4527/ad47dd","url":null,"abstract":"\u0000 V0405 Dra is a W UMa-type binary star. Basing on the TESS data, we have conducted an orbital period study and performed a light curve analysis for the system. The orbital period study reveals that the $O-C$ curve for V0405 Dra exhibits secular decrease at an extremely high rate of $dP/dt = -2.71 times 10^{-6} daycdot year^{-1}$, along with periodic variations characterized by an amplitude of $A_3 = 0.0032$ days and a period of $P_3 = 1.413 $ years. The orbital periodic change is possibly due to the light-travel time effect resulting from an additional third body in the system, for which we estimate a minimum mass of $M_3 = 0.77 M_{odot}$. By employing the add{2013 version of the} Wilson-Devinney (W-D add{2013}) method to synthesize light curve, we derived photometric solutions indicating that V0405 Dra is a new deep ($f = 68.7%$)and low-mass ratio ($q =0.175$) contact binary. The fast decrease in its orbital period is likely caused by mass transfer from the more massive primary star to the less massive secondary star, or due to angular momentum loss, which have been elaborated upon in the last section. With further mass transfer and loss of angular momentum, the binary will gradually evolve into a tighter contact configuration, eventually leading to a merge into a single star, following the evolutionary paths suggested for such deep and low mass ratio contact binaries.","PeriodicalId":509923,"journal":{"name":"Research in Astronomy and Astrophysics","volume":"30 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141007938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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