Experimental Astronomy最新文献

{"title":"Pitch angle measurement method based on detector counts distribution. -I. basic conception","authors":"Chenwei Wang,&nbsp;Shaolin Xiong,&nbsp;Yi Zhao,&nbsp;Hongbo Xue,&nbsp;Yiteng Zhang,&nbsp;Shanzhi Ye,&nbsp;Wei Xu,&nbsp;Jinpeng Zhang,&nbsp;Zhenghua An,&nbsp;Ce Cai,&nbsp;Peiyi Feng,&nbsp;Ke Gong,&nbsp;Haoxuan Guo,&nbsp;Yue Huang,&nbsp;Xinqiao Li,&nbsp;Jiacong Liu,&nbsp;Xiaojing Liu,&nbsp;Xiang Ma,&nbsp;Liming Song,&nbsp;Wenjun Tan,&nbsp;Jin Wang,&nbsp;Ping Wang,&nbsp;Yue Wang,&nbsp;Xiangyang Wen,&nbsp;Shuo Xiao,&nbsp;Shenglun Xie,&nbsp;Yanbing Xu,&nbsp;Wangchen Xue,&nbsp;Sheng Yang,&nbsp;Zhenghang Yu,&nbsp;Dali Zhang,&nbsp;Wenlong Zhang,&nbsp;Peng Zhang,&nbsp;Shuangnan Zhang,&nbsp;Yanqiu Zhang,&nbsp;Yanting Zhang,&nbsp;Zhen Zhang,&nbsp;Xiaoyun Zhao,&nbsp;Chao Zheng,&nbsp;Shijie Zheng","doi":"10.1007/s10686-025-10027-7","DOIUrl":"10.1007/s10686-025-10027-7","url":null,"abstract":"<div><p>As an X-ray and gamma-ray all-sky monitor designed to observe high-energy astrophysical transients, Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) has also made a series of observational on burst events of gamma-rays and particles in the low Earth orbit. Pitch angle is one of the key parameters of charged particles traveling around the geomagnetic field. However, the usage of the all-sky monitor (GECAM-style) instruments to measure the pitch angle of charged particles is still lacking. In this work, we propose a novel method for GECAM and similar instruments to measure the pitch angle of charged particles based on detector counts distribution. The basic concept of this method, along with supporting simulation studies, is presented. With this method, the pitch angle of a peculiar electron precipitation event detected by GECAM-C is derived to be about 90<span>(^circ)</span>, demonstrating the feasibility of our method. We note that the application of this method on GECAM-style instruments may open a new window for studying space particle events, such as Terrestrial Electron Beams (TEBs) and Lightning-induced Electron Precipitations (LEPs). </p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145510527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Estimation of (mu) and y distortions in the cosmic microwave background with COBE/FIRAS data","authors":"Somita Dhal,&nbsp;Koustav Konar,&nbsp;R. K. Paul","doi":"10.1007/s10686-025-10035-7","DOIUrl":"10.1007/s10686-025-10035-7","url":null,"abstract":"<div><p>This paper presents a novel approach to estimate the <span>(mu)</span> and y-distortions in the Cosmic Microwave Background (CMB) using the COBE/FIRAS data. The analysis draws from the concept of blackbody radiation inversion (BRI), a mathematical technique typically used to determine the temperature distribution from a radiated power spectrum. We study the deviations from the ideal blackbody spectrum or the spectral distortions by incorporating first a non-zero chemical potential <span>(mu)</span> via the Bose-Einstein distribution and then also adding the Compton parameter <i>y</i> while keeping the monopole temperature constant. We infer the results as probability distribution functions on these distortions. Finally, we derive <span>(mu = {(-,0.656 ;pm ; 2.048) times 10^{-5}})</span> and <span>(y = {5.498 times 10^{-10} pm 2.775 times 10^{-6}})</span> at a <span>(68%)</span> confidence interval. Here we show how the BRI method performs in a test-case scenario, illustrating its potential for extracting spectral distortion parameters in CMB.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145456593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Space VLBI-exploring the potential of hybrid orbit configurations","authors":"Abhirup Datta,&nbsp;Tiasha Biswas,&nbsp;Harsha Avinash Tanti,&nbsp;Samit Kumar Pal","doi":"10.1007/s10686-025-10031-x","DOIUrl":"10.1007/s10686-025-10031-x","url":null,"abstract":"<div><p>Space-Based Very Long Baseline Interferometry (SVLBI) significantly enhances the resolution and sensitivity of radio astronomical observations by placing radio telescopes in orbit. However, designing an effective satellite constellation for SVLBI is complex, as it involves multiple factors such as imaging performance, (<i>u</i>, <i>v</i>) coverage, resolution, and image fidelity. This paper is the first in a series focused on evaluating the (<i>u</i>, <i>v</i>) coverage capabilities of different satellite configurations. We investigated several constellation designs, including hybrid configurations that combine satellites in various orbital regimes. These hybrid setups demonstrated superior performance compared to those using satellites in a single orbit. Notably, a configuration with five satellites—three in Medium Earth Orbit (MEO) and two in Low Earth Orbit (LEO)—achieved the most uniform and dense (<i>u</i>, <i>v</i>) coverage with the fewest satellites. Finally, the most effective configurations were further tested using simplified simulations involving both point sources and extended sources to assess their practical imaging capabilities.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145456622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 multi-site study of radio environment for cosmology experiments","authors":"Yash Agrawal,&nbsp;Saurabh Singh,&nbsp;Girish B. S.,&nbsp;Somashekar R.,&nbsp;Srivani K. S.,&nbsp;Raghunathan A.,&nbsp;Vishakha S. Pandharpure,&nbsp;Udaya Shankar N.,&nbsp;Keerthipriya S.,&nbsp;Mayuri Sathyanarayana Rao","doi":"10.1007/s10686-025-10036-6","DOIUrl":"10.1007/s10686-025-10036-6","url":null,"abstract":"<div><p>Radio Frequency Interference (RFI) presents a significant challenge for carrying out precision measurements in radio astronomy. In particular, RFI can be a showstopper when looking for faint cosmological signals such as the red-shifted 21-cm line from cosmic dawn (CD) and epoch of reionization (EoR). As wireless communications, satellite transmissions, and other RF technologies proliferate globally, understanding the RFI landscape has become essential for site selection and data integrity. We present findings from RFI surveys conducted at four distinct locations: three locations in India, the Gauribidanur Radio Observatory in Karnataka, Twin Lakes in Ladakh, Kalpong Dam in the Andaman Islands, and the Gruvebadet Atmosphere Laboratory in Ny-Ålesund, Svalbard, Norway. These sites, selected based on their geographical diversity and varying levels of human activity, were studied to assess RFI presence in 30-300 MHz bands, critical for low-frequency observations and experiments targeting the 21-cm CD/EoR signal. Using an automated RFI detection approach via the Hampel filter and singular value decomposition, the surveys identified both persistent and transient interference, which varies with location and time. The results provide a comprehensive view of the RFI environment at each site, informing the feasibility of long-term cosmological observations and aiding in the mitigation of RFI in radio astronomical data. The methods developed to characterize RFI can be easily generalized to any location and experiment.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145406376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Characterization of a half wave plate and a polarizer for accurate starlight polarimetry","authors":"Paolo de Bernardis,&nbsp;Silvia Masi,&nbsp;Giulia Barbieri Ripamonti,&nbsp;Fabio Columbro","doi":"10.1007/s10686-025-10029-5","DOIUrl":"10.1007/s10686-025-10029-5","url":null,"abstract":"<div><p>In the process of developing a space-based imaging Stokes polarimeter for starlight polarization measurements, we established a procedure to characterize its two main optical components: the wave plate and the polarizer. We demonstrate that a simple optical bench setup combined with a custom calibration procedure can be used to measure the non-ideality parameters of both the polarizer and the wave plate. Using this approach, we characterized two high-quality components for the V-band. We set an upper limit for the cross-polarization of the polarizer, <span>(C_B le 1 times 10^{-4})</span>, and a limit of <span>(Delta le 2 times 10^{-4})</span> for the transmission imbalance of the half-wave plate. We show that with these components the setup yields reproducible measurements at the level of <span>(0.001%)</span> for the polarization degree of a weakly polarized source, and <span>(3')</span> for the position angle. We also investigate the performance of the components under tilted incidence, up to <span>(6^o)</span> off-axis, as required for a wide-field imaging version of a stellar polarimeter. We find that within this range, even without any off-axis bias correction, these components enable measurements of the polarization degree with an accuracy better than 0.005, and of the polarization angle with an accuracy better than <span>(1^o)</span>.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-025-10029-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145405543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extracting stellar clusters with gaia data: core and tail members","authors":"Stéphane Leon,&nbsp;Taufiq Hidayat,&nbsp;Amatul Firdausya Nur Cahyaningtyas,&nbsp;Gilles Bergond,&nbsp;Emilio J. Alfaro","doi":"10.1007/s10686-025-10034-8","DOIUrl":"10.1007/s10686-025-10034-8","url":null,"abstract":"<div><p>The Gaia mission led to a complete revision of our knowledge of the open cluster ecology in the Galaxy thanks to the access to new or more accurate structural and dynamical parameters of the stellar clusters. With access to a large set of stellar data in the Galaxy, we aim to reevaluate the identification and extraction of stellar clusters utilizing Gaia data. These new characterizations will be the baseline to build a new catalogue of local open clusters. The described method groups stars in an 8-fold space based on positions, velocities, magnitude, and colors using a DBSCAN algorithm. It optimizes the DBSCAN parameters and the data weighting to find the best solutions. It makes use of an Approximate Bayesian Computation (ABC) method because the traditional likelihood function is missing. The core and the external tidal tail memberships can be retrieved separately. The new unsupervised extraction method on Gaia data has proved to be efficient on benchmark stellar cluster targets. The method was implemented in the high performance Julia language and was released on the GitHub platform.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145405584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 synergies between Twinkle and Ariel: a pilot study","authors":"Andrea Bocchieri,&nbsp;Luke Booth,&nbsp;Lorenzo V. Mugnai","doi":"10.1007/s10686-025-10032-w","DOIUrl":"10.1007/s10686-025-10032-w","url":null,"abstract":"<div><p>Launching in 2027 and 2029, respectively, <i>Twinkle</i> and <i>Ariel</i> will conduct the first large-scale homogeneous spectroscopic surveys of the atmospheres of hundreds of diverse exoplanets around a range of host star types for statistical understanding. This will fundamentally transition the field to an era of population-level characterisation. In this pilot study, we aim to explore possible synergies between <i>Twinkle</i> and <i>Ariel</i> to determine for instance whether prior <i>Twinkle</i> observations can substantially inform the target selection and observing strategy of <i>Ariel</i>. This study primarily aims to encourage further investigation by both consortium communities by showing what a potential scientific synergy would look like on a promising scientific case that requires further exploration. For this aim, we select a small subset of ‘cool’ planets that are also particularly well-suited to be observed by <i>Twinkle</i> and therefore <i>Ariel</i>. By using representative noise estimates for both missions, we compute the number of visits required for an observation. Then, we simulate and retrieve transmission spectra of each target, assuming gaseous, H<span>(_2)</span>/He-dominated atmospheres and various atmospheric models to test different scenarios. For all candidates, we find that atmospheric parameters are generally retrieved well within 1–<span>(sigma)</span> to input values, with <i>Ariel</i> typically achieving tighter constraints. We also find that retrieved values may depend on the tier when <i>Ariel</i> can achieve Tier 3 in a single visit, due to the information loss that may occur in binning. We demonstrate that for a small subset of cool gaseous planets, exploitable synergies exist between <i>Twinkle</i> and <i>Ariel</i> observations and <i>Twinkle</i> may very well provide a vantage point to plan <i>Ariel</i> observations. The true extent of the potential synergies, far beyond our considered sample, will be determined by the final target lists. Once Twinkle is operational and its performance is known, it could reliably inform Ariel’s target prioritization and Ariel’s capabilities which are already well-established can help define optimal targets and observational approaches for Twinkle. Therefore, further exploration of potential synergies is highly warranted especially after Twinkle is operational and Ariel’s launch date approaches.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 3","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-025-10032-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145341381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study and reproducibility of the SRG/eROSITA background with particle rejection on and off","authors":"Emanuele Perinati,&nbsp;Michael J. Freyberg,&nbsp;Christian Pommranz,&nbsp;Muhammed M. Serim,&nbsp;Michael C. H. Yeung,&nbsp;Konrad Dennerl,&nbsp;Susanne Friedrich,&nbsp;Chris Tenzer,&nbsp;Andrea Santangelo","doi":"10.1007/s10686-025-10028-6","DOIUrl":"10.1007/s10686-025-10028-6","url":null,"abstract":"<div><p>For more than six years SRG/eROSITA is the first X-ray telescope in orbit around the second Lagrangian point in the Sun-Earth system. We present an updated study of its instrumental background based on cleaned data and improved simulations, carried out in the framework of the eROSITA Background Working Group. We examine the standard observing mode with minimum ionising particle rejection switched on as well as the non-standard mode with particle rejection switched off, which was set from time to time to monitor the overflow trails and patterns left by energetic particles. We show that, in the first case, Geant4 simulations allow to reproduce quite well the measured residual background; in the second case, the simulations support the analysis and interpretation of the observed trails, though a peculiar feature of a small minority of them, which apparently split from one frame into the next one, is not reflected in the simulations.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-025-10028-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145256088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MCA-Net: a method based on deep learning for the classification of low-resolution stellar spectra","authors":"Hao Li","doi":"10.1007/s10686-025-10033-9","DOIUrl":"10.1007/s10686-025-10033-9","url":null,"abstract":"<div><p>Classification of stellar spectra plays a crucial role in astronomical research, providing a wealth of valuable data and laying a solid foundation for humanity’s journey to explore the universe. However, existing studies often focus on the extraction of local features from stellar spectra, such as identifying peaks and troughs, which presents challenges for practical applications. While balancing stellar categories and their quantities, there remains room for improvement in classification accuracy. This study presents a new neural network, MCA-Net, which integrates convolutional neural networks with local feature extraction capabilities, long short-term memory networks adept at sequential data analysis, and attention mechanisms designed for long sequence mining. The aim is to effectively extract features from stellar spectral data and perform classification. The research utilizes stellar spectral data captured by the LAMOST telescope, encompassing classification tasks across three-class (F, G, K) and ten-class (A0, A5, F0, F5, G0, G5, K0, K5, M0, M5). Comparative experiments validated the effectiveness of the proposed method and network, demonstrating very high accuracy and F1-Score results in classification. The MCA-Net was tested using an independent test set, achieving an accuracy of 95.32% in the three-class classification task and an accuracy of 98.11% in the ten-class classification task.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145256691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"DMD-based Multi-Object Spectrograph (D-MOS): AIV and first light results","authors":"Sriram S,&nbsp;Vineeth Valsan,&nbsp;Remya B. S,&nbsp;Subramaniam A,&nbsp;Maheswar G","doi":"10.1007/s10686-025-10024-w","DOIUrl":"10.1007/s10686-025-10024-w","url":null,"abstract":"<div><p>A Digital Micromirror Device (DMD)-based Multi-Object Spectrograph (D-MOS) with an integrated imager has been developed. The optical performance of the MOS is evaluated through comprehensive laboratory calibration and on-sky observations using the 1.3-meter J.C. Bhattacharya (JCB) Telescope at the Vainu Bappu Observatory (VBO). The system is designed to assess the viability of using a DMD as a programmable slit mechanism for future ultraviolet-optical space missions. A complete imager-cum-spectrograph assembly was constructed using off-the-shelf optical components and configured for operation in the optical band, employing a DLP9500 DMD with a 1920<span>(times)</span>1080 micromirror array. Calibration experiments established the DMD-to-detector coordinate mapping and validated the strategies for object selection and slit placement. On-sky tests in crowded stellar fields confirmed successful slit targeting, precise object alignment, and multiplexed spectral acquisition. The spectrograph achieved a peak efficiency of 32%, a spectral resolving power of R<span>(sim)</span>1000 at 6000Å, a multiplexing capability of up to 46 slits (extendable to 85), and a contrast ratio of <span>(sim)</span> 6000. These results demonstrate the robustness and effectiveness of the DMD MOS system under real observational conditions and raise its TRL level for use in next-generation spectroscopic space missions.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"60 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145256673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}