arXiv subjects

Shuang-nan Zhang

Publications and source records attributed to Shuang-nan Zhang.

3 recordsLinked to original sources

arXiv2025

Fast Transitions of X-ray Variability in the Neutron Star Low Mass X-ray Binary Cygnus X-2

We present a spectral-timing analysis of two NICER observations of the weakly magnetized neutron star low-mass X-ray binary Cygnus X-2. During these observations, we detect a rapid transition from a narrow 50-Hz horizontal-branch oscillation to a broad 5-Hz normal-branch oscillation, accompanied by an increase in source flux and a decrease in spectral hardness. Thanks to the large effective area of NICER, we are able to conduct a detailed comparison of the spectra associated with different types of quasi-periodic oscillations (QPOs) on short timescales. By fitting the spectra with a model that includes a disc and Comptonization components plus two emission lines, we find that the parameters of the disc component do not change significantly during the transition. However, assuming a fixed electron temperature, the optical depth of the Comptonization component decreases significantly. This drop in optical depth may be attributed to the expansion of the boundary layer or spreading layer.In addition, we find that the rms spectra for both the HBO and NBO are hard, suggesting that the boundary layer or spreading layer is driving the variability. We discuss the potential physical origin of the different types of QPOs.

astro-ph.HE↗

arXiv2020

In-flight calibration of the Insight-Hard X-ray Modulation Telescope

We present the calibration of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) X-ray satellite, which can be used to perform timing and spectral studies of bright X-ray sources. Insight-HXMT carries three main payloads onboard: the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME) and the Low Energy X-ray telescope (LE). In orbit, the radioactive sources, activated lines, the fluorescence lines and celestial sources are used to calibrate the energy scale and energy resolution of the payloads. The Crab nebular is adopted as the primary effective area calibrator and empirical functions are constructed to modify the simulated effective areas of the three payloads respectively. The systematic errors of HE, compared to the model of the Crab nebular, are less than 2% in 28--120 keV and 2%--10% above 120 keV. The systematic errors of ME are less than 1.5% in 10--35 keV. The systematic errors of LE are less than 1% in 1--7 keV except the Si K--edge (1.839 keV, up to 1.5%) and less than 2% in 7--10 keV.

astro-ph.IM↗

arXiv2016

Study of linearity of LYSO crystal for HERD calorimeter

The High Energy cosmic Radiation Detection (HERD) facility is a space mission designed for detecting cosmic ray (CR) electrons, $γ$-rays up to tens of TeV and CR nuclei from proton to iron up to several PeV. The main instrument of HERD is a 3-D imaging calorimeter (CALO) composed of nearly ten thousand cubic LYSO crystals. A large dynamic range of single HERD CALO Cell (HCC) is necessary to achieve HERD's PeV observation objectives, which means that the response of HCC should maintain a good linearity from minimum ionizing particle (MIP) calibration to PeV shower maximum. In order to study the linearity of HCC over such a large energy range, a beam test has been implemented at the E2 and E3 beam lines of BEPC. High intensity pulsed electron beam provided by E2 line are used for producing high energy density within HCC; $π^{+}$/proton provided by E3 line are used for HCC calibration. The results show that no saturation effect occurs and the linearity of HCC is better than 10% from 30 MeV (1 MIP) to 1.1$\times$10$^{3}$ TeV (energy density is 93 TeV/cm$^{3}$), which can meet the requirement mentioned above.

physics.ins-det↗