Experimental Astronomy最新文献

We propose a future mission concept, the MeV Astrophysical Spectroscopic Surveyor (MASS), which is a large area Compton telescope using 3D position sensitive cadmium zinc telluride (CZT) detectors optimized for emission line detection. The payload consists of two layers of CZT detectors in a misaligned chessboard layout, with a total geometric area of 4096 cm(^2) for on-axis observations. The detectors can be operated at room-temperature with an energy resolution of 0.6% at 0.662 MeV. The in-orbit background is estimated with a mass model. At energies around 1 MeV, a line sensitivity of about (10^{-5}) photons cm(^{-2}) s(^{-1}) can be obtained with a 1 Ms observation. The main science objectives of MASS include nucleosynthesis in astrophysics and high energy astrophysics related to compact objects and transient sources. The payload CZT detectors weigh roughly 40 kg, suggesting that it can be integrated into a micro- or mini-satellite. We have constructed a pathfinder, named as MASS-Cube, to have a direct test of the technique with 4 detector units in space in the near future.

The Chasing All Transients Constellation Hunters (CATCH) space mission is an intelligent constellation consisting of 126 micro-satellites in three types (A, B, and C), designed for X-ray observation with the objective of studying the dynamic universe. Currently, we are actively developing the first Pathfinder (CATCH-1) for the CATCH mission, specifically for type-A satellites. CATCH-1 is equipped with Micro Pore Optics (MPO) and a 4-pixel Silicon Drift Detector (SDD) array. To assess its scientific performance, including the effective area of the optical system, on-orbit background, and telescope sensitivity, we employ the Monte Carlo software Geant4 for simulation in this study. The MPO optics exhibit an effective area of 41 cm(^2) at the focal spot for 1 keV X-rays, while the entire telescope system achieves an effective area of 29 cm(^2) at 1 keV when taking into account the SDD detector’s detection efficiency. The primary contribution to the background is found to be from the Cosmic X-ray Background. Assuming a 625 km orbit with an inclination of (29^circ ), the total background for CATCH-1 is estimated to be (8.13times 10^{-2}) counts s(^{-1}) in the energy range of 0.5–4 keV. Based on the background within the central detector and assuming a Crab-like source spectrum, the estimated ideal sensitivity could achieve (1.9times 10^{-12}) erg cm(^{-2}) s(^{-1}) for an exposure of 10(^4) s in the energy band of 0.5–4 keV. Furthermore, after simulating the background caused by low-energy charged particles near the geomagnetic equator, we have determined that there is no need to install a magnetic deflector.

The solar gravitational lens (SGL) provides a factor of (10^{11}) amplification for viewing distant point sources beyond our solar system. As such, it may be used for resolved imaging of extended sources, such as exoplanets, not possible otherwise. To use the SGL, a spacecraft carrying a modest telescope and a coronagraph must reach the SGLs focal region, that begins at (sim )550 astronomical units (AU) from the Sun and is oriented outward along the line connecting the distant object and the Sun. No spacecraft has ever reached even a half of that distance; and to do so within a reasonable mission lifetime (e.g., less than 25 years) and affordable cost requires a new type of mission design, using solar sails and microsats ((<100) kg). The payoff is high – using the SGL is the only practical way we can ever get a high-resolution, multi-pixel image of an Earth-like exoplanet, one that we identify as potentially habitable. This paper describes a novel mission design starting with a rideshare launch from the Earth, spiraling in toward the Sun, and then flying around it to achieve solar system exit speeds of over 20 AU/year. A new sailcraft design is used to make possible high area to mass ratio for the sailcraft. The mission design enables other fast solar system missions, starting with a proposed very low cost technology demonstration mission (TDM) to prove the functionality and operation of the microsat-solar sail design and then, building on the TDM, missions to explore distant regions of the solar system, and those to study Kuiper Belt objects (KBOs) and the recently discovered interstellar objects (ISOs) are also possible.

HERMES Pathfinder is an in-orbit demonstration consisting of a constellation of six 3U nano-satellites hosting simple but innovative detectors for the monitoring of cosmic high-energy transients. The main objective of HERMES Pathfinder is to prove that accurate position of high-energy cosmic transients can be obtained using miniaturized hardware. The transient position is obtained by studying the delay time of arrival of the signal to different detectors hosted by nano-satellites on low-Earth orbits. In this context, we need to develop novel tools to fully exploit the future scientific data output of HERMES Pathfinder. In this paper, we introduce a new framework to assess the background count rate of a spaceborne, high energy detector; a key step towards the identification of faint astrophysical transients. We employ a neural network to estimate the background lightcurves on different timescales. Subsequently, we employ a fast change-point and anomaly detection technique called Poisson-FOCuS to identify observation segments where statistically significant excesses in the observed count rate relative to the background estimate exist. We test the new software on archival data from the NASA Fermi Gamma-ray Burst Monitor (GBM), which has a collecting area and background level of the same order of magnitude to those of HERMES Pathfinder. The neural network performances are discussed and analyzed over period of both high and low solar activity. We were able to confirm events in the Fermi-GBM catalog, both solar flares and gamma-ray bursts, and found events, not present in Fermi-GBM database, that could be attributed to solar flares, terrestrial gamma-ray flashes, gamma-ray bursts and galactic X-ray flashes. Seven of these are selected and further analyzed, providing an estimate of localisation and a tentative classification.

The paper presents a methodology for the digitization and processing of our own spectral data archive and the results of comparing the obtained data with those of modern observations. An Epson Perfection V850 Pro scanner with optional SilverFast8 software was used to scan photographic films. More than 2,000 archive spectra of Seyfert galaxies obtained in 1970–1990 with the AZT-8 telescope have been scanned to date (resolution 2400 dpi). The work describes the reduction of distortion for the scanned spectra using the program code, created in Python. Our code has been registered on the web service “GitHub” and a link to the code is given in the work. The results of digitization and subsequent spectra processing are presented in the example of the Seyfert galaxy Mrk 3. For the absolute calibration of the early spectra (Jan. 25, 1976) the radiation fluxes in the emission lines of [SII] were used. The lines were measured on the modern spectrogram obtained in 2023 on telescope AZT-8 (Mar. 14, 2023)

Pix.PAN is a compact cylindrical magnetic spectrometer, intended to provide excellent high energy particle measurements under high rate and hostile operating conditions in space. Its principal design is composed of two Halbach-array magnetic sectors and six Timepix4-based tracking layers; the latest hybrid silicon pixel detector readout ASIC designed. Due to Pix.PAN’s compact and relatively simple design, it has the potential to be used for space missions exploring with measurements of unprecedented precision, high energy particles in radiation belts and the heliophere (solar energetic particles, anomalous and galactic cosmic rays). In this white paper, we discuss the design and expected performance of Pix.PAN for COMPASS (Comprehensive Observations of Magnetospheric Particle Acceleration, Sources, and Sinks), a mission concept submitted to NASA’s Call “B.16 Heliophysics Mission Concept Studies (HMCS)” in 2021 that targets the extreme high energy particle environment of Jupiter’s inner radiation belts. We also discuss PixPAN’s operational conditions and interface requirements. The conceptual design shows that is possible to achieve an energy resolution of<12% for electrons in the range of 10 MeV-1 GeV and<35% for protons between (sim )200 MeV to a few GeV. Due to the timestamp precision of Timepix4, a time resolution (on an instrument level) of about 100 ps can be achieved for time-of-flight measurements. In the most intense radiation environments of the COMPASS mission, Pix.PAN is expected to have a maximum hit rate of 44(frac{text {MHz}}{text {cm}^2}) which is below the design limit of 360(frac{text {MHz}}{text {cm}^2}) of Timepix4. Finally, a sensor design is proposed which allows the instrument to operate with a power budget of 20W without the loss of scientific performance.

In this paper, the wavefront perturbation method based on power detection of radio sources is used to measure the surface error of the Tianma radio telescope. By measuring the surface errors at different elevation angles, a surface compensation model to correct gravitational deformation is established. Observation results shows that the efficiency reduction caused by the gravitational deformation can be effectively compensated by loading this model on the active surface, especially at high and low elevations. A dual-beam calibration scheme is further used to remove atmospheric background fluctuations, which significantly improves data quality at lower elevations. The form and order of the perturbation modes and data processing are optimized to improve measurement accuracy. This paper presents the first attempt to apply the wavefront perturbation method to large radio telescopes and demonstrates its capacity and effectiveness in telescope runtime surface measurement and maintenance.

In an ideal germanium detector, fully-absorbed monoenergetic (gamma )–rays will appear in the measured spectrum as a narrow peak, broadened into a Gaussian of width determined only by the statistical properties of charge cloud generation and the electronic noise of the readout electronics. Multielectrode detectors complicate this picture. Broadening of the charge clouds as they drift through the detector will lead to charge sharing between neighboring electrodes and, inevitably, low-energy tails on the photopeak spectra. We simulate charge sharing in our germanium cross strip detectors in order to reproduce the low-energy tails due to charge sharing. Our goal is to utilize these simulated spectra to develop an analytical fit (shape function) for the spectral lines that provides a robust and high-quality fit to the spectral profile, reliably reproduces the interaction energy, noise width, and the number of counts in both the true photopeak and the low-energy tail, and minimizes the number of additional parameters. Accurate modeling of the detailed line profiles is crucial for both calibration of the detectors as well as scientific interpretation of measured spectra.

Time series reconstruction of astronomical catalogues is an important part of data archiving and a basis for time-domain astronomical analysis in the era of time-domain astronomy. As the field of view and sampling frequency of various time-domain telescopes increase, the amount of data to be processed becomes larger and larger. How to optimize the spatial and temporal efficiency of this process with the aid of computer technology becomes a hot issue. To address the problem of spatial efficiency, in this paper, we propose a time series data compression algorithm based on the negative database and dynamic programming, and on this basis, we design a multi-level storage and access query architecture for hot data and non-hot data, which greatly compresses the storage space of data while ensuring the query efficiency. To address the issue of time efficiency, this paper proposes a spatio-temporal data partitioning and layout algorithm suitable for distributed architecture, whose nested round-robin strategy has a wide range of load balancing effects on different spatial locations, temporal locations, and different ranges of temporal data queries, which can effectively ensure the execution efficiency of the distributed system. Experimental results show that the proposed optimization algorithm can keep the system at a low load skewness level of about 4% and save about 83% of storage space.

We use synthetic model spectra to investigate the potential of near-ultraviolet (3000-4050 Å) observations of massive O-type stars. We highlight the He I (lambda )3188 and He II (lambda )3203 pair as a potential temperature diagnostic in this range, supported by estimates of gravity using the high Balmer series lines. The near-ultraviolet also contains important metallic lines for determinations of chemical abundances (oxygen in particular) and estimates of projected rotational velocities for O-type spectra. Using the model spectra we present performance estimates for observations of extragalactic massive stars with the Cassegrain U-Band Efficient Spectrograph (CUBES) now in construction for the Very Large Telescope. The high efficiency of CUBES will open-up exciting new possibilities in the study of massive stars in external galaxies. For instance, CUBES will provide new insights into the physical properties of O-type stars, including oxygen abundances, in metal-poor irregular galaxies at (sim )1 Mpc from integrations of just 2-3 hrs. Moreover, CUBES will bring quantitative spectroscopy of more distant targets within reach for the first time, such as the O-type star (V (sim ) 21.5 mag) in Leo P (at 1.6 Mpc) in only half a night of observations.