Sky Monitor Research Articles

Recent Outbursts of the High-mass X-Ray Binary CI Camelopardalis

Recent Outbursts of the High-mass X-Ray Binary CI Camelopardalis

Preliminary study of the multi—physics design for the support structure of LEM—X space mission

In this modern space exploration era, the lunar site offers new opportunities such as the deployment of an X—ray observatory capable of observing half of the sky simultaneously, but also may allowing access to the entire solid angle by exploiting the rotation of the moon around its own axis.The Lunar Electromagnetic Monitor in X—rays (LEM—X) is an All Sky Monitor for the X—ray band (2–50 keV) based on the concept of coded aperture camera. The basic element is the camera of the Wide Field Monitor and the concept is to realize a ”dome” composed of N identical modules that observe different directions, thus covering an overall simultaneous field of view of 2π in the sky. In this paper, we describe the preliminary study of a support structure for that camera, the design solutions adopted for the most important thermo—mechanical drivers, which have been elaborated and used for the demonstration of compliance to the system requirements with the environment. In particular, we reported some different thermal and mechanical scenario of this preliminary structure and the optimization of critical components with innovative and accurate fem analysis.

SAINT (Small Aperture Imaging Network Telescope)—A Wide-Field Telescope Complex for Detecting and Studying Optical Transients at Times from Milliseconds to Years

In this paper, we present a project of a multi-channel wide-field optical sky monitoring system with high temporal resolution—Small Aperture Imaging Network Telescope (SAINT)— mostly built from off-the-shelf components and aimed towards searching and studying optical transient phenomena on the shortest time scales. The instrument consists of twelve channels each containing 30 cm (F/1.5) GENON Max objectives mounted on separate ASA DDM100 mounts with pointing speeds up to 50 deg/s. Each channel is equipped with a 4128 × 4104 pixel Andor Balor sCMOS detector and a set of photometric griz filters and linear polarizers. At the heart of every channel is a custom-built reducer-collimator module allowing rapid switching of an effective focal length of the telescope—due to it the system is capable of operating in either wide-field survey or narrow-field follow-up modes. In the first case, the field of view of the instrument is 470 square degrees (39 sq.deg. for a single channel) and the detection limits (5σ level at 5500 Å) are 12.5, 16.5, 19, 21 with exposure times of 20 ms, 1 s, 30 s and 20 min, correspondingly. In the second, follow-up (e.g., upon detection of a transient of interest by either a real-time detection pipeline, or upon receiving an external trigger) regime, all telescopes are oriented towards the single target, and SAINT becomes an equivalent to a monolithic 1-meter telescope, with the field of view reduced to 11′ × 11′, and the exposure times decreased down to 0.6 ms (1684 frames per second). Different channels may then have different filters installed, thus allowing a detailed study—acquiring both color and polarization information—of a target object with the highest possible temporal resolution. The telescopes are located in two pavilions with sliding roofs and are controlled by a cluster of 25 computers that both govern their operation and acquire and store up to 800 terabytes of data every night, also performing its real-time processing using a dedicated fast image subtraction pipeline. Long-term storage of the data will require a petabyte class storage. The operation of SAINT will allow acquiring an unprecedented amount of data on various classes of astrophysical phenomena, from near-Earth to extragalactic ones, while its multi-channel design and the use of commercially available components allows easy expansion of its scale, and thus performance and detection capabilities.

Proposal of optical sky monitoring with subsecond cadence

Proposal of optical sky monitoring with subsecond cadence

Very high energy sky monitoring with the Southern Wide-field Gamma-ray Observatory

The Southern Wide-field Gamma-ray Observatory (SWGO) is the proposal for a new ground-based γ-ray instrument in the Southern Hemisphere, which will use an array of water-Cherenkov based particle detectors to provide continuous monitoring and regular scanning of a large portion of the sky at the very- and ultra-high-energies (VHE and UHE, respectively). At the low energy side, SWGO aims to push the observational range of wide-field ground-based γ-ray facilities down to a few hundred GeV, thus bridging the gap between space and ground-based facilities in the monitoring of the VHE sky. In the high energy domain, on the contrary, it will benefit from the optimal coverage of the Galactic Plane to map the distribution of UHE sources in the inner parts of the Galactic disk and close to the Galactic Center, leading to an extraordinary improvement in our ability to identify their most likely counterparts. In this contribution, we describe the concept of SWGO and its potential to constrain the physics of VHE emission and particle acceleration in γ-ray sources powered by relativistic jets and energetic shocks. We finally discuss its role within the global network of multi-messenger facilities.

Very high energy sky monitoring with the Southern Widefield Gamma-ray Observatory

The Southern Wide-field Gamma-ray Observatory (SWGO) is the proposal for a new ground-based γ-ray instrument in the Southern Hemisphere, which will use an array of water-Cherenkov particle detectors to provide continuous monitoring of a large portion of the sky at the very- and ultra-high-energies (VHE and UHE, respectively). At the low energy side, SWGO aims to push the observational range of wide-field ground-based γ-ray facilities down to a few hundred GeV, thus bridging the gap between space and ground-based facilities in the monitoring of the VHE sky. In the high energy domain, on the contrary, it will benefit from the optimal coverage of the Galactic Plane to map the distribution of UHE sources in the inner parts of the Galactic disk and close to the Galactic Center, leading to an extraordinary improvement in our ability to identify their most likely counterparts. In this contribution, we describe the concept of SWGO and its potential to constrain the physics of VHE emission and particle acceleration in γ-ray sources powered by relativistic jets and energetic shocks. We finally discuss its role within the global network of multi-messenger facilities.

First Wide Field-of-view X-Ray Observations by a Lobster-eye Focusing Telescope in Orbit

As a novel X-ray focusing technology, lobster-eye micropore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel, the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy, a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in 2022 July, has a mostly unvignetted field of view of 18.°6 × 18.°6. Its spatial resolution is in the range of 4′–7′ in FWHM and the focal spot effective area is 2–3 cm2, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1, and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5–4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster-eye MPO.

Probing Gamma-Ray Burst VHE Emission with the Southern Wide-Field-of-View Gamma-Ray Observatory

Recent observations have confirmed that Gamma-Ray Burst (GRB) afterglows produce Very High-Energy radiation (VHE, E>100GeV). This highly anticipated discovery opens new scenarios in the interpretation of GRBs and in their role as probes of Extragalactic Background Light (EBL) and Lorentz Invariance Violation (LIV). However, some fundamental questions about the actual nature of VHE emission in GRBs and its evolution during the burst are still unsolved. These questions will be difficult to address, even with future imaging Cherenkov telescopes, such as the Cherenkov Telescope Array (CTA). Here we investigate the prospects of gamma-ray sky monitoring with Extensive Air Showers arrays (EAS) to address these problems. We discuss the theoretical aspects connected with VHE radiation emission and the implications that its temporal evolution properties have on the interpretation of GRBs. By revisiting the high-energy properties of some Fermi-LAT detected GRBs, we estimate the typical fluxes expected in the VHE band and compare them with a range of foreseeable instrument performances, based on the Southern Wide Field-of-view Gamma-ray Observatory concept (SWGO). We focus our analysis on how different instrument capabilities affect the chances to explore the burst onset and early evolution in VHE, providing invaluable complementary information with respect to Cherenkov telescope observations. We show that under the assumption of conditions already observed in historical events, the next-generation ground monitoring detectors can actually contribute to answer several key questions.

Identifying distinct metrics for assessing night sky brightness

ABSTRACT Studying light pollution is an interest to researchers in a wide range of fields including astronomy, biology, civil engineering, ecology, and social science. Consequently, numerous sky brightness metrics have been developed over the years. However, what metrics are truly representative of the night sky quality and unique to the measured feature? The US National Park Service Night Skies Program has collected more than 1500 sets of night skies data throughout the United States. For each data set, a maximum of 56 metrics were measured through the combination of the captured images, Sky Quality Meter readings, and visual observations. This paper analyses these measurements and identifies a distinctive set of night sky brightness metrics based on the principal component analysis. Three major findings emerge. First, the commonly used metrics, such as the zenith brightness, horizontal illuminance, maximum vertical illuminance, all-sky light pollution ratio, Bortle class, and limiting magnitude, are highly correlated. Secondly, the observed sky brightness often offers a good estimate of the artificial light level despite the natural varying night sky background. Thirdly, a set of six metrics that consists of the zenith brightness and sky brightness percentiles are more distinctive when used to concisely describe night sky characteristics. These findings suggest that long-term night sky monitoring can be efficiently carried out by measuring the sky brightness percentiles on the observed all-sky images.

CHARACTERIZATION OF MODERN CCD AND CMOS SENSORS FOR SKY SURVEYS

Here we review the efforts we take in a newly established laboratory inside Institute of Physics in Prague in order to characterize modern large-format CCD and CMOS sensors for sky survey applications. While the laboratory is primarily established in order to participate in low-level CCD sensor characterization for LSST project, we also managed to perform a thorough laboratory testing of recently released Andor Marana sCMOS (which is especially interesting for wide-field sky monitoring applications due to its large format, backilluminated design, high achievable frame rate and low read-out noise), as well as detailed measurements of response non-linearity of Moravian Instruments G4-16000 CCD cameras (based on large-format Kodak KAF-16803 chip) used in several robotic telescopes. We briefly review the results acquired on these cameras, as well as hardware and software we developed for the laboratory.

Analyzing the gamma-ray activity of neutrino emitter candidates: comparing TXS 0506+056 with other blazars

Abstract On 22nd of September 2017 the IceCube collaboration sent an alert for an EHE (Extreme High Energy) event, corresponding to the reconstruction of a muonic neutrino (IC-170922A) with energy ∼290 TeV. A multi-wavelength follow-up campaign associated this neutrino event with a gamma-ray flaring state of the BL Lac TXS 0506+056 located at z=0.3365. From the same position of the sky a muonic neutrino excess is observed in a time window of 110 days around 13th of December 2014. These observations together suggest TXS 0506+056 as a possible neutrino emitter. We report here a long term gamma-ray monitoring of this source and we compare it with other blazars spatially correlated with astrophysical muonic neutrino events observed by IceCube. We characterize the most significant gamma-ray flares of the blazars in the sample and introduce the blazar duty cycle as an important parameter to be considered when assessing a possible neutrino counterpart. For the selected blazars we show the expected neutrino flux variability with different time binning assuming the gamma-rays observed by Fermi-LAT as a product of a leptohadronic emission scenario. The neutrino expectations from the blazar sample are then compared with the IceCube discovery flux searching for the optimal time bin in a multi-messenger context. This analysis indicates that the detection of a single flare represents a challenge for a single cubic kilometer detector, underlining the importance of increasing the size of current neutrino telescopes and obtaining a good monitoring of the entire sky through a global neutrino network.

A Sea–Sky Line Detection Method Based on the RANSAC Algorithm in the Background of Infrared Sea–Land–Sky Images

Subgrade sea and sky monitoring equipment requires the accurate detection of threat targets in a given area. Due to the extremely complex sea–land–sky backgrounds, the sea–sky line is often submerged in the background. Therefore, we propose an algorithm for accurately detecting sea–sky lines under a complex sea–land–sky background. Based on the analysis of infrared images with sea–land–sky backgrounds, we segment images using the k-means algorithm. To use the random sampling consistency (RANSAC) algorithm to fit the sea–sky line better, we divide the images into nonuniform segments and count the row mean-value gradient trough. The experimental results show that the sea–sky line can be detected in 1215 out of 1227 pictures. The test success rate is 99%, and the difference from the actual sea–sky line is less than 3 pixels. The method presented has higher adaptability under a subgrade sea and sky monitoring environment.

MVN experiment – All sky monitor for measuring cosmic X-ray background of the universe onboard the ISS

MVN experiment – All sky monitor for measuring cosmic X-ray background of the universe onboard the ISS

Regional Climate Monitoring and Assessment in the Belt and Road

The Belt and Road is the abbreviation of the Silk Road Economic Belt and the 21st Century Maritime Silk Road. The countries along the Belt and Road routes are generally highly sensitive and vulnerable to climate change, so it is urgent to design a service platform for climate change prediction and monitoring. In this paper, based on the various demands of climate change prediction and monitoring, we analyzed the importance of the establishment of a climate service platform and the main measures to improve the capabilities of climate service platform. According to the principle of “refinement, systematization and specialization”, a meteorological service platform was designed, which are based on space remote sensing, supplemented by airborne remote sensing, and verified by the ground observation network to verify that the real-time monitoring and prediction of sky and ground integration. The platform can provide scientific basis for the countries along the routes, and improve the infrastructure construction progress and personnel safety along the Belt and Road.

A ΔR ∼ 9.5 mag Superflare of an Ultracool Star Detected by the SVOM/GWAC System

Abstract We report the detection and follow-up of a superstellar flare GWAC 181229A with an amplitude of ΔR ∼ 9.5 mag on an M9-type star by SVOM/GWAC and the dedicated follow-up telescopes. The estimated bolometric energy E bol is (5.56–9.25) × 1034 erg, which makes the event one of the most powerful flares seen on ultracool stars. The magnetic strength is inferred to be 3.6–4.7 kG. Thanks to sampling with a cadence of 15 s, a new component near the peak time with a very steep decay is detected in the R-band light curve, followed by the two-component flare template given by Davenport et al. An effective temperature of 5340 ± 40 K is measured by fitting a blackbody shape to the spectrum in the shallower phase during the flare. The filling factors of the flare are estimated to be ∼30% and 19% at the peak time and at 54 minutes after the first detection. The detection of this particular event with large amplitude, huge emitted energy, and a new component demonstrates that high-cadence sky monitoring cooperation with fast follow-up observations is very important for understanding the violent magnetic activity.

PSF Estimation in Crowded Astronomical Imagery as a Convolutional Dictionary Learning Problem

We present a new algorithm for estimating the Point Spread Function (PSF) in wide-field astronomical images with extreme source crowding. Robust and accurate PSF estimation in crowded astronomical images dramatically improves the fidelity of astrometric and photometric measurements extracted from wide-field sky monitoring imagery. Our radically new approach utilizes convolutional sparse representations to model the continuous functions involved in the image formation. This approach avoids the need to detect and precisely localize individual point sources that is shared by existing methods. In experiments involving simulated astronomical imagery, it significantly outperforms the recent alternative method with which it is compared.

Advances in Chinese polar scientific exploration using high-altitude balloons

Polar Regions, which generally refer to Antarctica and the Arctic, play a key role in global change and are optimal locations for space observation. The expansion of polar exploration and research regarding global climate issues and development of future environmental policies has become important and debated worldwide. China has been conducting research in Polar Regions since 1980 and has accomplished a series of scientific achievements. However, China’s polar investigations began somewhat later that those of Europe and the United States, with insufficient observational data and limited diversity of detection platforms. To solve the problem, high-altitude scientific balloons have been used as an important means to help China rapidly to advance exploration in Polar Regions. High-altitude balloons offer many advantages, such as stable flight for several months, strong carrying capacity, flexibility with experiments, low cost, and fast recovery. For many years, the United States, Japan, Europe, and other developed countries have used high-altitude scientific balloons to conduct polar scientific experiments. Polar Regions are ideal for long-term scientific exploration using high-altitude balloons due to polar vortices (atmospheric circulation), continuous solar radiation (summer polar days), and especially because there are no airspace restrictions in Antarctica. The Chinese Academy of Sciences has carried out multiple space exploration projects using high-altitude balloons at Xianghe Station since 1978 and has conducted a series of experiments using high-altitude balloons at the ice-laden “Third Pole” in the Qinghai-Tibet Plateau in collaboration with the Aerospace Information Research Institute. Sixteen high-altitude balloon flight tests were successfully deployed in 2019. Within the field of high-altitude balloons for near-space exploration, China has an excellent scientific research team and technical foundation that is at par with those of other countries. However, scientific exploration based on high-altitude balloon platforms in Polar Regions remains challenging. To serve the relevant national strategies, it is needed to define major scientific questions in polar exploration and conduct research in a timely manner. Owing to the unique advantages of polar regions, China can carry out polar exploration using high-altitude balloon platforms for a variety of tasks (e.g., in-situ measurement, dropsonde sounding, astronomical observation, and remote sensing) from different scientific disciplines, such as environmental science, atmospheric science, space weather, planetary observation, solar physics, and biological research). Based on China’s current balloon exploration capabilities, relevant work will be carried out step by step from earth observation, sky monitoring to near-space detection, aiming at an integrated capability. The specific research subjects include: (1) Polar ice sheet change; (2) polar geological environment studies; (3) polar habitat monitoring; (4) polar space environment monitoring; (5) polar atmosphere detection; (6) polar near-space biological research; (7) planetary science; and (8) astronomical observation. High-altitude balloons will also play an important role in future studies involving in-situ measurement and dropsonde sounding, astronomical observation, and remote sensing, which will further enhance China’s scientific research in the Polar Regions. This will enhance China’s status and legitimacy in the peaceful use and development of Polar Regions and would give China more clout internationally in polar affairs.

Calibration of the instrumental response of Insight-HXMT/HE CsI detectors for gamma-ray monitoring

The CsI detectors of the High Energy X-ray Telescope of the Hard X-ray Modulation Telescope (HXMT/CsI) can be used for gamma-ray all sky monitoring and searching for the electromagnetic counterpart of gravitational wave source. The instrumental responses are mainly obtained by Monte Carlo simulation with the Geant4 tool and the mass model of both the satellite and all the payloads, which is updated and tested with the Crab pulse emission in various incident directions. Both the Energy-Channel relationship and the energy resolution are calibrated in two working modes (Normal-Gain mode & Low-Gain Mode) with the different detection energy ranges. The simulative spectral analyses show that HXMT/CsI can constrain the spectral parameters much better in the high energy band than that in the low energy band. The joint spectral analyses are performed to ten bright GRBs observed simultaneously with HXMT/CsI and other instruments (Fermi/GBM, Swift/BAT, Konus-Wind), and the results show that the GRB flux given by HXMT/CsI is systematically higher by 7.0±8.8% than those given by the other instruments. The HXMT/CsI-Fermi/GBM joint fittings also show that the high energy spectral parameter can be constrained much better as the HXMT/CsI data are used in the joint fittings.

The AGILE data center and its legacy

We present an overview of the main AGILE Data Center activities and architecture. AGILE is a space mission of the Italian Space Agency (ASI) in joint collaboration with INAF, INFN, CIFS, and with the participation of several Italian space industry companies. The AGILE satellite was launched on April 23, 2007, and is devoted to the observation of the gamma-ray Universe in the 30 MeV -- 50 GeV energy range, with simultaneous X-ray imaging capability in the 18-60 keV band. The AGILE Data Center, part of the ASI multi-mission Space Science Data Center (SSDC, previously known as ASDC) is in charge of all the scientific operations: data management, archiving, distribution of AGILE data and scientific software, and user support. Thanks to its sky monitoring capability and fast ground segment alert system, AGILE is substantially improving our knowledge of the gamma-ray sky, and provides a crucial contribution to multimessenger follow-up of gravitational waves and neutrinos

Progress with the Geological and Ecological Survey in the Critical Zone of the Global Black Soil Which is Linked with the Sky and Ground Monitoring Methods (ICGP665)

Progress with the Geological and Ecological Survey in the Critical Zone of the Global Black Soil Which is Linked with the Sky and Ground Monitoring Methods (ICGP665)