Experimental Astronomy最新文献

Pulsar observation scheduling is a highly dynamic problem with uncertainty caused by scintillation and environmental interference. In the scheduling systems used by observatories today, this uncertainty is usually accounted for by using a short-term scheduling process. In order to observe as many pulsars as possible within a certain period of time, it becomes imperative for multiple telescopes or sub-arrays to observe multiple targets at the same time. However, there is little research on the speed improvement and cost-efficiency improvement of such “parallel" observation with multiple telescopes. In this work, we have designed a multiple telescope short-term scheduling simulation system, based on extending previously proposed scheduling heuristics using a single telescope pulsar scheduling simulator. Additionally, we propose a more complex multiple telescope short-term scheduling policy based on the multiple travelling salesperson problem (mTSP). Realistic datasets within the simulation environment are used to evaluate the proposed algorithms with multiple telescopes. The results show that multiple telescopes can significantly reduce the time to observe a set of pulsars. The previous single telescope heuristics adapt surprisingly well to the multiple telescope scenario and the novel mTSP policy is competitive, with potential for future improvements.

Context: CARMENES is a dual-channel high-resolution spectrograph at the 3.5 m Calar Alto telescope designed to detect low-mass planets around late-type dwarfs by measuring their radial velocities (RVs). High thermal stability in both the visible (VIS) and near-infrared (NIR) channels is essential to achieve the precision required for these measurements. In particular, stabilising the NIR channel to the millikelvin level, which operates at cryogenic temperatures ( (sim) 140 K), poses significant engineering challenges. Purpose: The CARMENES-PLUS project was initiated to improve the instrument’s intrinsic RV precision. In this article, we focus on the thermal stability improvements made to the NIR channel’s cooling system. Methods: The NIR cooling system was originally conceived to operate with a discontinuous flow of cryogenic nitrogen gas. As part of CARMENES-PLUS, this was upgraded to a continuous flow configuration. Additional changes included the installation of an automatic vacuum system, a proportional control valve, and a pressure regulation system. These upgrades were designed to reduce thermal fluctuations and enhance long-term stability. Results: The implemented upgrades significantly improved the intrinsic RV precision of the NIR channel. We quantified this improvement using Fabry-Pérot calibration spectra, obtaining an intrinsic RV precision of 0.67 m s(^{-1}) after the interventions, an improvement of nearly 2 m s(^{-1}). We also assessed the stability of the nightly zero points, finding a reduced scatter of 3.9 m s(^{-1}) post-upgrade, compared to 6.1 m s(^{-1}) before. For a sample of slowly rotating stars ((v sin i_star le) 2 km s(^{-1})), the median scatter decreased from 8.8 m s(^{-1}) to 6.7 m s(^{-1}) after the upgrades. Conclusions: These results demonstrate that the thermal control upgrades introduced in CARMENES-PLUS have enhanced the NIR channel’s RV performance, bringing it closer to the VIS channel’s stability and reinforcing CARMENES’s capabilities for exoplanet detection around M dwarfs.

The Compton Spectrometer and Imager (COSI) is an upcoming NASA Small Explorer satellite mission, designed for all-sky observations in the soft gamma-ray domain with the use of germanium detectors (GeDs). An active Anticoincidence System (ACS) of BGO scintillators surrounds the GeDs to reduce the background and contribute to the detection of transient events. Accurately modeling the ACS performance requires simulating the intricate scintillation processes within the shields, which significantly increases the computational cost. We have encoded these effects into a correction matrix derived from dedicated Geant4 simulations with the inclusion of the optical physics. For this purpose, we use laboratory measurements for the energy and spatial response of the ACS lateral wall to benchmark the simulation and define instrument parameters, including the BGO absorption length and the electronic noise. We demonstrate that the simulations replicate the experimental energy resolution and light collection uniformity along the BGO crystal, with maximum discrepancies of 20% and 10%, respectively. The validated simulations are then used to develop the correction matrix for the lateral wall, accounting for the light collection efficiency and energy resolution based on the position within the crystal. The gamma-ray quantum detection efficiency is also position-dependent via the inclusion of the optical physics. It is enhanced by (sim)8% close to the SiPMs and suppressed by (sim)2% in the adjacent corners with respect to the average value. Finally, we explore the energy threshold and resolution of the bottom ACS, considering the impact of its smaller crystals compared with the lateral walls.

The VGOS 13m radio telescope located in Chiang Mai, Thailand is the first VGOS standard station built overseas by China. This station expands Chinese very long baseline interferometry (VLBI) network (CVN) and furthers multiple scientific goals, such as continuous monitoring of Earth orientation parameters and research into the terrestrial and celestial reference frames. The station is equipped with a wideband 2-14GHz receiver and an X/Ka dual-frequency receiver, a fast-slewing antenna, a DBBC3 high-speed data acquisition terminal and a high-speed recording terminal. This is aimed at improving observation efficiency and research quality. We developed the Remote Health Monitoring System (RHMS) specifically for the VGOS 13m radio telescope located in Thailand. This system integrates Tango Controls’ distributed middleware technology, allowing it to furnish the observation team with comprehensive historical and real-time status updates for the Chiang Mai VGOS station. Additionally, it promptly issues alerts for abnormalities, thereby improving the station’s unmanned monitoring, maintenance and operations capabilities, and operational performance. It also provides a feasible solution for remote monitoring of future overseas VGOS stations.

We present a novel laboratory astrophysics experiment to obtain photoabsorption spectra of neutral and near neutral atomic species in the near infrared (NIR) spectral region. A laser produced plasma containing the ions of interest is probed by the collimated output of a supercontinuum fiber laser. The resulting absorption spectrum is recorded on a 0.75-m spectrograph equipped with a complimentary metal oxide semiconductor (CMOS) camera. Spectra of yttrium plasmas were recorded 11 (upmu )s after its formation in the range from 700 to 1100 nm, and we present the spectrum between 708 to 832 nm to illustrate the capabilities of the technique. In this range we found 26 lines previously identified and 29 lines not previously identified. The importance of new atomic structure data, in particular transition energies and relative oscillator strengths, is highlighted in the context of increasingly sophisticated ground and space-based spectrometers in the era of multi-messenger astronomy. Future developments and improvements are briefly discussed.

We report on the follow-up observations with XMM-Newton of two X-ray binary candidates identified in the first eROSITA all-sky survey data (eRASS1), 1eRASS J061330.8(+)160440 and 1eRASS J161201.9−464622. Based on the obtained results, in particular, the observed X-ray spectra and lack of pulsations, as well as properties of the identified optical counterparts, we conclude that both candidates are unlikely to be XRBs. Based on LAMOST optical spectroscopy and SED fit results for 1eRASS J061330.8(+)160440 we classify it as an M0 chromospherically active subgiant star. ZTF and TESS photometry reveal highly significant period for this object of 7.189 days, which likely attributed to starspot(s). On the other hand, SALT follow-up spectroscopy of 1eRASS J161201.9−464622 solidly classifies this source as a bright novalike cataclysmic variable (CV), the second discovered with eROSITA. A persistent 4.802 h signal is found across all three available TESS observations, and is tentatively identified as the orbital period of the binary. Follow-up high-speed photometry and time-resolved spectroscopy are required to confirm the derived orbital modulation.

The Enhanced X-ray Timing and Polarimetry Mission (eXTP) is a flagship collaborative Sino-European X-ray mission currently in its Phase B study, led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS). One of the primary instruments contributed by the European consortium to eXTP is the Large area detector (LAD), which consists of 40 modules of Silicon Drift Detector (SDD) operating in the 2–30 keV energy range. The Back-End Electronics (BEE) for the LAD are organized at two hierarchical levels: Module Back-End Electronics (MBEE) and Panel Back-End Electronics (PBEE), to manage the large number of detectors in the instrument. The Module Back-End Electronics (MBEE) acquires data from 8 Front-End Electronics (FEE) boards, which constitute half of a module and additionally preprocesses the acquired digital data. The PBEE, positioned one level higher in the hierarchy, is responsible for aggregating the data streams (science telemetry and Housekeeping (HK) data) from 20 MBEE to the Instrument Control Unit (ICU) using a single SpaceWire connection. Additionally, it distributes power, telecommands, and synchronized timing information from the ICU to the MBEE. The BEEs are designed using radiation-tolerant embedded and programmable logic systems to support data acquisition, processing, telecommand handling, and HK collection. This paper discusses the architecture of the LAD and its electronics system, with a focus on the BEE, and presents the test results and performance derived from a single-line LAD data acquisition chain setup.

In the field of time-domain sky surveys, traditional single-sensor cameras have a limited field of view, making it challenging to efficiently complete large-scale survey tasks. Cameras composed of multiple mosaicked sensors, enables telescopes to achieve wide-field, high-resolution imaging, greatly enhancing survey efficiency. The Camera Control System (CCS) is responsible for controlling the operation of devices in mosaic camera systems, monitoring their status in real-time, coordinating them to complete the full operational workflow, and ultimately generating scientific image data. In this paper, we present an in-depth study of the system architecture for large distributed mosaic cameras and we propose the RACS2-CCS framework, based on the second-generation Remote Autonomous Control System (RACS2). The core feature of RACS2-CCS is its event-driven mechanism. In this framework, we not only establish a unified component programming paradigm but also introduce a range of new features, including component management, image file management, and a site interface, addressing the limitations of RACS2 when applied to the control of large mosaic camera systems. RACS2-CCS was built through the gradual implementation of the hardware control layer, system control layer, and interface layer. RACS2-CCS was successfully applied to the CCS of the Wide Field Survey Telescope (WFST). During multiple joint debugging sessions, the system performed stably and successfully completed long-term observation tasks at the Lenghu observatory, verifying its efficiency and reliability in real-world operations.

The Vainu Bappu Telescope (VBT) is a 2.34-m reflector, primarily supported on-axis field of view, offering high-resolution and low-to-medium resolution spectroscopic observations in its prime and Cassegrain configurations. This study presents the design and fabrication of a compact, lightweight, three-element wide-field corrector (WFC) utilizing three spherical lenses to cover a polychromatic wavelength range over a 30(') FoV at prime focus. The WFC design was optimized using ZEMAX, ensuring precision in aberrations, tolerances, and atmospheric dispersion. The fabricated lenses met stringent tolerances, with a ±1 mm deviation in radius of curvature and ±2 mm deviation in center thickness. A mechanical mount was developed to integrate all the WFC lenses, and wavefront error testing for the WFC system was performed using ZYGO interferometry, yielding a Wavefront Error of 0.05 (lambda ). Laboratory performance tests were designed and conducted using a dedicated setup with achromatic lenses and 100 (mu m) fiber-coupled polychromatic light source showed a deviation of 0.1 pixel on-axis and 0.5 pixel at the extreme off-axis field compared to the ZEMAX design, demonstrating that the optical performance of WFC is with minimal aberrations across the entire FoV. The successful integration of the WFC at the VBT prime focus will increase the FoV, enabling the multi-fiber, multi-spectrograph setup in (30^{prime }) field that will facilitate both OMR and Echelle spectrograph to be used on the same night along with the addition of new multi-object spectrograph and an integral field unit instrument. This will mark a significant upgrade for the VBT, broadening its research potential, and expanding its observational versatility.

In this publication, we continue a series of investigations carried out in the High Atlas, in particular at Oukaïmdan and Aklim, by identifying a new astronomical site in the Beni Mellal mountains, notably at Tassemit. At present, we rely on satellites to gather meteorological and geophysical data. The analysis of atmospheric turbulence and wind speed distribution is of crucial importance in the evaluation of astronomical sites and the implementation of adaptive optics systems. This study examines optical turbulence using a general model, as well as wind characteristics at Tassemit. The data used come from reanalyses (ERA5) of the European Centre for Meteorological Forecasting, covering a 10-year period. We study vertical variations and seasonal trends in wind speed and atmospheric turbulence. At a pressure level of 200 hPa, wind speeds (V_{200}) show lower levels in summer and autumn, with the exception of November, while they are higher in winter and spring. At Tassemit, extreme values of (V_{200}) are observed in April, reaching 26.87 (mathrm {ms^{-1}}), and in August, with a minimum of 12.32 (mathrm {ms^{-1}}). Furthermore, the locations of the peaks in the (C_{n}^2) profiles correspond to the tropopause and jet stream regions at the Tassemit site. In addition, the aim of this work is to calculate the astroclimatic parameters for the qualification of the astronomical sites ((r_{textrm{0}}), and (theta _{textrm{0}})). The initial data come from the Tassemit site. The medians of the (r_{textrm{0}}) and (theta _{textrm{0}}) values are 11.19 cm and 1.65 arcsec accordingly, offering a possible point of reference for astronomical uses.