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

Nanoindentation and Thermal Study of Polyvinylalcohol/graphene Oxide Nanocomposite Film Through Organic/inorganic Assembly

In this study, hydrogen-bonding interactions between polyvinylalcohol (PVA) and graphene oxide (GO) were utilized as the driving force to fabricate organic/inorganic PVA nanocomposite films with homogeneous dispersion of GO. The nanomechanical and nanotribological performances of pure PVA and PVA/GO films were investigated by using nanoindentation technique. The results demonstrated that the incorporation of 0.5 wt% GO in PVA gives the highest improvement in nanomechanical and nanotribological properties. Compared to pure PVA, the elastic modulus and hardness of 0.5 wt% GO/PVA were notably increased by 122.8% and 64.5%, respectively. Furthermore, the film showed self-lubrication effect and enhanced anti-scratch performance. TGA study reveals an enhanced maximum decomposing temperature of 68.4 °C with the addition of 0.5 wt% GO in PVA. The stability of hydrogen bonding between PVA and GO accompanied with the formed organic/inorganic assembled lamellar micro-structure of PVA/GO films is the main reason for the distinct improvements in nanomechanical, nanotribological and thermal properties of PVA/GO nanocomposite films

Investigation of the Tribological Properties: Core-Shell Structured Magnetic Ni@NiO Nanoparticles Reinforced Epoxy Nanocomposites

Epoxy resin (EP) nanocomposites reinforced with core-shell structured magnetic Ni@NiO nanoparticles (NPs) were fabricated by using a surface wetting method. The mechanical and tribological properties of the varied EP nanocomposites were comparatively investigated. Results revealed that 5 wt.% Ni@NiO NPs was the optimal content for Ni@NiO/EP nanocomposites to achieve the best mechanical and tribological properties. The 5 wt.% Ni@NiO/EP nanocomposites exhibited 37.8%, 16.3% and a 22.2-fold increase in hardness, elastic modulus and wear resistance, respectively. Meanwhile, the effect of Ni@NiO NPs on the tribological properties of Ni@NiO/EP nanocomposites were also investigated by the observations of scanning electron microscopy (SEM)