Spectral and Timing Analysis of the Black Hole Transient MAXI J1631–479 During its 2019 Outburst Observed with Insight-HXMT

We report spectral and timing analysis of the black hole transient MAXI J1631–479 during the hard intermediate state of its 2019 outburst from the Insight-Hard X-ray Modulation Telescope(Insight-HXMT)observations.We find that the energy dependence of the type-C quasi-periodic oscillation(QPO)frequency evolves with time:during the initial rise of a small flare(~MJD 58526.0-58527.1),the QPO frequency increases with increasing energy from~1 to~100 ke V,and then the frequency remains constant after MJD 58527.1.We discover a possible new phenomenon of Fe line’s QPO frequency jump that has never been observed for other black hole transients:during the small flare,the QPO frequency around the Fe line energy is higher than any other energy band,with the frequency difference Δf=0.25±0.08 Hz between 5.5–7.5 ke V and other energy bands.The spectral analysis shows that the evolution of QPOs is related to the equivalent width of the narrow Fe line,and its equivalent width increases during this small flare.We propose that the QPO frequency difference results from the differential precession of a vertically extended jet,and the higher QPO frequency of Fe line could be caused by the layered jet when the jet scale increases.At the same time,the evolution of QPOs is related to the accretion rate,while the energy dependence of QPOs supports the existence of deceleration in the vertically distributed jet.

Revisiting Laser-Intensity-Dependent Ionization and Fragmentation of C60

We revisit the laser-intensity-dependent ionization and fragmentation yields of C60 molecules irradiated by 25-fs,798-nm laser pulses based on the approach in which photoions are measured via a velocity map imaging spectrometer working in a time-sliced mode.This approach dramatically improves the signal-to-background ratio compared to those using a simple(traditional)time-of-flight mode(spectrometer),and thus allows us to measure the laser-intensity dependences down to a previously untouched region,which is expected to provide new insights into the intense-field ionization and fragmentation of C60.Indeed,we find that the saturation intensities for C60 ionizations and the onset intensity for C60 fragmentation are much lower than those reported in previous experiments.Furthermore,the derived saturation-intensity dependence on charge distribution demonstrates the validity of the over-the-barrier ionization using a conducting sphere model.

Size and Interface Effects on Tensile Strength of Polymers with Nano/Micro Particle Inclusions

Polymers with particle inclusions have wide applications,and the mechanical properties of polymer composites affect their reliability in service.The strength of these composites is dependent on factors such as particle fraction,size,distribution,and interface interaction between the two phases,in addition to the properties of the polymers and particles.The size effect of particles and interface damage play an important role and thus draw considerable attention.In this paper,the size-and interface-dependent strength of polypropylene(PP)with nano/micro silica(SiO_(2))particles of different fractions is studied through a combination of tensile experiments on a series of samples and corresponding three-dimensional(3D)finite element modeling.The results indicate that PP with 2%SiO_(2)nanoparticles of 50 nm exhibits relatively higher tensile strength,shedding light on the microstructure mechanism where smaller particle sizes lead to better interface bonding.Furthermore,the particle size and interface coupling effect is analyzed based on the size-dependent elastic modulus model and the interface-cohesive model.The simulation demonstrates the local interface damage evolution around a particle of the composites in tension.These findings are beneficial for designing polymer composites with nanoparticle inclusions.