Experimental Astronomy最新文献

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, (C_B le 1 times 10^{-4}), and a limit of (Delta le 2 times 10^{-4}) for the transmission imbalance of the half-wave plate. We show that with these components the setup yields reproducible measurements at the level of (0.001%) for the polarization degree of a weakly polarized source, and (3') for the position angle. We also investigate the performance of the components under tilted incidence, up to (6^o) 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 (1^o).

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.

Launching in 2027 and 2029, respectively, Twinkle and Ariel 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 Twinkle and Ariel to determine for instance whether prior Twinkle observations can substantially inform the target selection and observing strategy of Ariel. 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 Twinkle and therefore Ariel. 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(_2)/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–(sigma) to input values, with Ariel typically achieving tighter constraints. We also find that retrieved values may depend on the tier when Ariel 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 Twinkle and Ariel observations and Twinkle may very well provide a vantage point to plan Ariel 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.

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.

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.

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(times)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(sim)1000 at 6000Å, a multiplexing capability of up to 46 slits (extendable to 85), and a contrast ratio of (sim) 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.

We report on results of the on-ground X-ray calibration of the Wide-field X-ray Telescope (WXT), built from novel lobster-eye micro-pore optics, on board the Einstein Probe (EP) satellite. To fully characterize the performance and properties of the WXT instrument, a series of tests and calibrations were conducted at different levels of devices, assemblies and the complete module before the launch of EP. In this paper, we present the calibration results of three flight model modules (FM1, FM5 and FM11) obtained during their end-to-end module calibration experiments carried out at the 100-m X-ray Test Facility (100XF) of the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS). Measurements of the Point Spread Function (PSF), effective area, and energy response were performed for multiple incident directions and several characteristic X-ray emission line energies. Specifically, the distributions of the PSF and effective areas are found to be roughly uniform across the FoV, in large agreement with the prediction of lobster-eye optics. Their energy-dependent behavior aligns well with theoretical predictions and Monte Carlo simulations. At (sim 1.25) keV, the full width at half maximum (FWHM) of the focal spot ranges from (3-7) arcmin (with a median of (sim 4.2) arcmin) and the effective area is in range of (sim 2-3~mathrm{cm^2}). Noticeably, the flight model instruments demonstrate a (sim 1.5) arcmin improvement in spatial resolution over the previously launched Lobster Eye Imager for Astronomy. The properties of the complementary metal-oxide semiconductor (CMOS) sensors were also calibrated. The gain coefficients are in range of (6.4-6.9~mathrm{eV/DN}). The energy resolutions are in range of (sim 120) to 140 eV at 1.25 keV, meeting design requirements. These calibration results have been ingested into the first version of calibration database (CALDB) and applied to the analysis of the scientific data acquired by WXT after the launch of EP.

The Low Energy X-ray Telescope (LE) is one of the three scientific instruments onboard the Insight-Hard X-ray Modulation Telescope (Insight-HXMT). Its primary scientific objectives include conducting both scanning and pointed observations within the soft X-ray band, specifically from 0.7 keV to 13 keV. The LE utilizes a Swept Charge Device (SCD) and forms a large-area array, achieving good energy resolution and time resolution. Due to exposure to space radiation, the performance of the detector gradually declines. By analyzing almost 7 years of LE onboard data, we studied the changes in detector performance and their underlying causes, including aspects such as readout noise, energy resolution, detector gain, and the proportion of split events. The results indicate that the readout noise increases continuously over time; the noise peak position drifts gradually; the energy resolution degrades at a rate of 50–60 eV per year, primarily due to the increasing charge transfer inefficiency; the detector gain decreases by approximately 0.8–1.3% each year; and the variation in the proportion of split events is only related to the detector threshold and is independent of space radiation. These studies provide important references for determining the LE observation plan and for analyzing the performance evolution of similar semiconductor detectors.

Telescope simulators may initially seem essential only for space telescopes, but they also have a significant impact on the development and operational processes of ground-based telescope instruments. Besides, the simulators for ground-based observatory telescopes are also functional as laboratory testing instruments for the development of new instruments or the evaluation of specific instruments. Considering this aspect, we present the design of an optical simulator as an on-off optical system for the Eastern Anatolia Observatory (DAG) Telescope with 4m diameter. We have planned to install this simulator on the Nasmyth platform of the DAG Telescope to be used as a maintenance, calibration and test assembly during non-observing periods because of the atmospheric conditions of the site of Eastern Anatolia Observatory (DAG; Doğu Anadolu Gözlemevi in Turkish). The simulator designed for the DAG Telescope will provide great convenience in completing the testing and calibration processes easily, and also saving time and manpower. In the production phase for the simulator, we plan to produce twin systems, one on the Nasmyth platform and the other in a laboratory. In this context, it will serve both design and test process in an optical laboratory environment and also in the real environment testing process of new optical systems on the Nasymth platform of the DAG Telescope located in the DAG site (Karakaya Hill, 3170 m altitude, Erzurum) of the Türkiye National Observatories.

The Digital Micromirror Device (DMD), a micro-electro-mechanical system (MEMS) consisting of individually controllable micromirrors, has emerged as a versatile tool for astronomical instrumentation, particularly in multi-object spectroscopy (MOS). Unlike traditional slit masks or fiber-based systems, DMDs offer dynamic reconfigurability, enabling efficient light modulation and enhanced spectral acquisition. Their adaptability has led to widespread adoption in ground-based spectrographs (e.g., RITMOS, BATMAN, SAMOS, IRMOS) and feasibility studies for space missions (e.g., EUCLID, CASTOR, SUMO, SIRMOS). DMDs have demonstrated robustness in space qualification tests, including radiation exposure, thermal cycling, and mechanical stress, making them viable for space-based applications. Recent advancements, such as UV-transparent windows and enhanced coatings, further expand their potential for ultraviolet astronomy. In India, the success of AstroSat’s Ultra Violet Imaging Telescope (UVIT) has motivated the development of the next-generation INdian Spectroscopic and Imaging Space Telescope (INSIST), which includes a DMD-based MOS for UV/optical observations. To advance its Technology Readiness Level (TRL), we evaluated the Texas Instruments DLP9500 DMD (1920 (times) 1080 micromirrors, 10 (upmu)m pitch) in the optical band, assessing key parameters such as diffraction efficiency, reflectivity, contrast, micromirror repeatability, and Point Spread Function (PSF) alignment. This study establishes a foundation for future UV-optimized DMD applications in INSIST and other astronomical missions.