The evolution of the corona in MAXI J1535-571 through type-C quasi-periodic oscillations with Insight-HXMT

Type-C quasi-periodic oscillations (QPOs) in black hole X-ray transients can appear when the source is in the low-hard and hard-intermediate states. The spectral-timing evolution of the type-C QPO in MAXI J1535-571 has been recently studied with Insight-HXMT. Here we fit simultaneously the time-averaged energy spectrum, using a relativistic reflection model, and the fractional rms and phase-lag spectra of the type-C QPOs, using a recently developed time-dependent Comptonization model when the source was in the intermediate state. We show, for the first time, that the time-dependent Comptonization model can successfully explain the X-ray data up to 100 keV. We find that in the hard-intermediate state the frequency of the type-C QPO decreases from 2.6 Hz to 2.1 Hz, then increases to 3.3 Hz, and finally increases to ~ 9 Hz. Simultaneously with this, the evolution of corona size and the feedback fraction (the fraction of photons up-scattered in the corona that return to the disc) indicates the change of the morphology of the corona. Comparing with contemporaneous radio observations, this evolution suggests a possible connection between the corona and the jet when the system is in the hard-intermediate state and about to transit into the soft-intermediate state.Comment: 11 pages, 6 figures, accepted for publication in MNRA

High energy Millihertz quasi-periodic oscillations in 1A 0535+262 with Insight-HXMT challenge current models

We studied the millihertz quasi-periodic oscillation (mHz QPO) in the 2020 outburst of the Be/X-ray binary 1A 0535+262 using Insight-HXMT data over a broad energy band. The mHz QPO is detected in the 27-120 keV energy band. The QPO centroid frequency is correlated with the source flux, and evolves in the 35-95 mHz range during the outburst. The QPO is most significant in the 50-65 keV band, with a significance of ~ 8 sigma, but is hardly detectable (<2 sigma) in the lowest (1-27 keV) and highest (>120 keV) energy bands. Notably, the detection of mHz QPO above 80 keV is the highest energy at which mHz QPOs have been detected so far. The fractional rms of the mHz QPO first increases and then decreases with energy, reaching the maximum amplitude at 50-65 keV. In addition, at the peak of the outburst, the mHz QPO shows a double-peak structure, with the difference between the two peaks being constant at ~0.02 Hz, twice the spin frequency of the neutron star in this system. We discuss different scenarios explaining the generation of the mHz QPO, including the beat frequency model, the Keplerian frequency model, the model of two jets in opposite directions, and the precession of the neutron star, but find that none of them can explain the origin of the QPO well. We conclude that the variability of non-thermal radiation may account for the mHz QPO, but further theoretical studies are needed to reveal the physical mechanism.Comment: 13 pages, 7 figures. Accepted for publication in MNRA

Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.Comment: 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.0443

Reconfigurable Modeling Method of Task-Oriented Architecture for Space Information Networks Based on DaaC

As an important national strategy infrastructure, the Space Information Network (SIN) is a powerful platform for future information support. The architecture model of the SIN is of great significance to the construction and development of the SIN. For the problems related to the poor versatility, portability, and recombination of the existing architecture modeling methods of the SIN, in this paper, based on the Data as a Center (DaaC) modeling idea, we propose a reconfigurable model of the task-oriented architecture of the SIN. Combining with the typical characteristics of the SIN, and drawing on the advantages of activity-based flexibility, service-oriented integrity, and object-oriented reusability, we propose a DaaC modeling idea with space data. The DaaC modeling idea can solve the problems related to the poor versatility and portability of the SIN architecture. Based on the DaaC idea, we analyze the requirements of the task-oriented architecture, and define the basic concepts of SIN reorganization, including the reconfigurable target, reconfigurable scheme, and reconfigurable SIN. We establish the reconfigurable principles of loose coupling, compatibility, isolation, and deconstruction. Meanwhile, we analyze the realization mechanism and methods of the task-oriented reconfigurable model of the SIN based on DaaC. Finally, we take a typical SIN as an example, and make a case study on land-based anti-missile combat activities as the task background based on the DoDAF2.0 (Department of Defense Architectural Framework 2.0) framework and the STK (Satellite Tool Kit) simulation platform. The case results are consistent with the theoretical expectation, and it verifies the feasibility and effectiveness of our proposed method

Research on Resource Allocation Method of Space Information Networks Based on Deep Reinforcement Learning

The space information networks (SIN) have a series of characteristics, such as strong heterogeneity, multiple types of resources, and difficulty in management. Aiming at the problem of resource allocation in SIN, this paper firstly establishes a hierarchical and domain-controlled SIN architecture based on software-defined networking (SDN). On this basis, the transmission, caching, and computing resources of the whole network are managed uniformly. The Asynchronous Advantage Actor-Critic (A3C) algorithm in deep reinforcement learning is introduced to model the process of resource allocation. The simulation results show that the proposed scheme can effectively improve the expected benefits of unit resources and improve the resource utilization efficiency of the SIN

Multi-Topology Routing Algorithms in SDN-Based Space Information Networks

Aiming at the complex structure of the space information networks (SIN) and the dynamic change of network topology, in order to design an efficient routing strategy, this paper establishes a SIN management architecture based on Software-defined Networking (SDN). A routing algorithm flow of the spatial information network based on a snapshot sequence is designed. For different spatial tasks with different Quality of Service (QoS) requirements, the concept of integrated link weight is proposed. The Warshall&ndash;Floyd algorithm is used to design the optimal routing strategy. A Task-oriented Bandwidth Resource Allocation (TBA) algorithm is proposed for multiple spatial tasks in the same link. Simulation results show that the algorithm can effectively guarantee the priority transmission of important tasks and avoid the unnecessary waste of bandwidth resources

Layer-Edge Patterns Exploration and Presentation in Multiplex Networks: From Detail to Overview via Selections and Aggregations

Multiplex networks have been widely used to describe the multi-type connections of entities in the real world. However, researches for multiplex networks visualization unilaterally focus on the presentation of topological structure, lacking of specific high-level information presentation for quantitative comparison of interlayer structure. Users cannot participate in the exploration and freely choose the layers (or sub-graphs, regions, etc.) of interest for structural comparison. Contraposing the layer-edge patterns visual analysis tasks of multiplex networks, this paper puts forward a novel solution for exploration and analysis that tightly couples topological structure and high-level patterns. It mainly contains a multi-force directed model to realize the balanced layout of nodes in multi-layer topology, as well as two kinds of high-level patterns of which the visual representations are, respectively, designed by a familiar metaphor&#8212;that is, the similar pattern representation based on the area-proportional Venn diagrams and the interaction pattern representation based on the directed arrows. Furthermore, views association is implemented through underlying data sharing and multiple interactions which can be used to gain insights through the creation of selections of interest and produce high-level infographic-style overviews simultaneously. The experiments on real-world data demonstrate the support of the proposed method for layer-edge patterns analysis tasks in multiplex networks and the effectiveness for analyzing the multi-layer structure of multiplex networks

Research on the Weighted Dynamic Evolution Model for Space Information Networks Based on Local-World

As an important national strategy infrastructure, the Space Information Network (SIN) is a powerful platform for future information support, and it plays an important role in many aspects such as national defense, people’s livelihood, etc. In this paper, we review typical and mainstream topology evolution models in different periods, and analyze the demand for studying the dynamic evolution model of SIN. Combining the concept and characteristics, we analyze the topology structure and local-world phenomenon of SIN, and define the dynamic topology model. Based on the system’s discussion of dynamic evolution rules, we propose a weighted local-world dynamic evolution model of SIN including the construction algorithm and implementation process. We achieve the quantitative analysis from four indicators including the node degree, node strength, edge weight, and correlation of strength and degree. Through the univariate control method, we analyze the impact on the network topology features of parameters: local-world M and extra traffic load α. Simulation results show that they have similar topology structure features with the theoretical analysis and real networks, and also verify the validity and feasibility of the proposed model. Finally, we summarize the advantages and disadvantages of the weighted local-world dynamic evolution model of SIN, and look forward to the future work. The research aim of this paper is to provide some methods and techniques to support the construction and management of SIN

SINDVis: User-Centered Dynamic Interactive Visualization System for Space Information Networks

As an important national strategy infrastructure, the Space Information Network (SIN) is a powerful platform for future information support. In this paper, we design and implement a user-centered, dynamic, interactive visualization system (SINDVis), and aim to assist multi-class users to understand, build, develop, maintain, and manage the SIN. We introduce the concept and architecture of SIN, summarize the key technologies of dynamic visualization and visual analysis, and analyze the basic characteristics of three types of users. Combining the content above, we design the architecture of SINDVis from an input module, a core-processing module, an output module, and a user body. We also describe eight basic functions of the entity domain view (GeoView) and topology domain view (TopolView). Meanwhile, we analyze the implementation methods of the GeoView and TopolView, including an improved Force-Directed Algorithm (FDA) layout, Fusion of Animation and Timeline (FAT) visualization, and Panning and Zooming (P&amp;Z) interactions. We analyze the experiment platforms and running environments of the GeoView and TopolView and realize the main contents of both views with a typical SIN. The results also verify the validity and feasibility of the theories and methods proposed. Finally, we discuss and analyze experimental results and the advantages and disadvantages of the SINDVis and look forward to future work. With the development of visualization and visual analysis technology, both application-driven and user-interaction features are gradually highlighted. We introduce the visualization technology into the field of SIN in order to provide new ideas for the basic theory and key technology research of SIN