Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to $\rm 150~keV$. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with $B\rm \sim 10^{13}~G$, $D\rm \sim 6~kpc$ and peak luminosity of $\rm >10^{39}~erg~s^{-1}$ which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.Comment: publishe

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

Construction of quality evaluation indicator system for diamond discrete global grid systems

Although the uniformity of diamond discrete global grid is essential for calculations and searches, geometric deformations increase with the level of divisions. The Goodchild Criteria provides a basis for evaluating the quality of the global grid. However, some indicators in the criteria are redundant and contradictory, and the existing indicator system has limitations. Directly using the indicator system may render the evaluation of the diamond grid unreliable. In this study, we summarized the evaluation indicators for grid quality based on the Goodchild Criteria, calculated the correlations between these indicators using different diamond grid systems, and constructed reliable evaluation systems based on similarities and differences. The selected grid systems are classified into two groups: non-equal-area and equal-area grids. Their quality evaluation systems are composed of Size-Shape-Topology Factor and Geometry-Topology Factor, respectively. The proposed quality evaluation systems utilize a minimal number of indicators selected from each factor to provide a comprehensive description of the diamond grid’s characteristics. This approach simplifies the complexity of the evaluations while improving their reliability and credibility

Reconstruction and evaluation of oil-degrading consortia isolated from sediments of hydrothermal vents in the South Mid-Atlantic Ridge

Abstract In this study, sediments were collected from two different sites in the deep-sea hydrothermal region of the South Atlantic Ocean. Two microbial enrichment cultures (H7S and H11S), which were enriched from the sediments collected at two sample sites, could effectively degrade petroleum hydrocarbons. The bacterial diversity was analyzed by high-throughput sequencing method. The petroleum degradation ability were evaluated by gas chromatography–mass spectrometry and gravimetric analysis. We found that the dominant oil-degrading bacteria of enrichment cultures from the deep-sea hydrothermal area belonged to the genera Pseudomonas, Nitratireductor, Acinetobacter, and Brevundimonas. After a 14-day degradation experiment, the enrichment culture H11S, which was obtained near a hydrothermal vent, exhibited a higher degradation efficiency for alkanes (95%) and polycyclic aromatic hydrocarbons (88%) than the enrichment culture H7S. Interestingly, pristane and phytane as biomarkers were degraded up to 90% and 91% respectively by the enrichment culture H11S, and six culturable oil-degrading bacterial strains were isolated. Acinetobacter junii strain H11S-25, Nitratireductor sp. strain H11S-31 and Pseudomonas sp. strain H11S-28 were used at a density ratio of 95:4:1 to construct high-efficiency oil-degrading consortium H. After a three-day biodegradation experiment, consortium H showed high degradation efficiencies of 74.2% and 65.7% for total alkanes and PAHs, respectively. The degradation efficiency of biomarkers such as pristane and high-molecular-weight polycyclic aromatic hydrocarbons (such as CHR) reached 84.5% and 80.48%, respectively. The findings of this study indicate that the microorganisms in the deep-sea hydrothermal area are potential resources for degrading petroleum hydrocarbons. Consortium H, which was artificially constructed, showed a highly efficient oil-degrading capacity and has significant application prospects in oil pollution bioremediation

Anchoring ultrafine Co3O4 grains on reduced oxide graphene by dual-template nanocasting strategy for high-energy solid state supercapacitor

Co3O4-based materials are regarded as superior electrode candidates in various energy storage devices due to their high theoretical capacity. Unfortunately, the poor electronic conductivity and huge volume expansion hamper their widespread applications. Therefore, nano-processing and introducing conductive matrix can view as the necessary methods to make Co3O4-based materials better for an advanced supercapacitor electrode. Herein, a dual-template nanocasting technique is proposed to design the ultrafine Co3O4 grains highly-dispersed on the reduced oxide graphene nanosheets (Co3O4/rGO-C), in which cetyltrimethyl ammonium bromide and silicate species are hired as the ideal soft and hard template, respectively. Co3O4 grains with size \u3c10 nm can expose more active sites and thus exert more redox activities to enhance the capacitive performance. In additional, ∼4 nm moderate pores are obtained in Co3O4/rGO-C after the hard template removing, which provides more diffusion channels for ion/electron rapid transport and also effectively alleviates the volume expansion on cycling. Consequently, the Co3O4/rGO-C electrode exhibits a remarkable specific capacitance (709.1 F g−1 at 1 A g−1) and long-term endurance (91.2% after 6000 cycles). Furthermore, an assembled solid-state asymmetric device of Co3O4/rGO-C||rGO delivers a super-high energy-density of 48.2 Wh kg−1 at 750.5 W kg−1. The high energy-density assists two devices in lightning a red light-emitting diode for 340 s. These results evidence the nanocasting strategy as an efficient method to achieve the advanced electrode materials for energy storage devices