arXiv subjects

J. L. Zeng

Publications and source records attributed to J. L. Zeng.

2 recordsLinked to original sources

arXiv2018

Analysis of the 3C445 Soft X-ray Spectrum as Observed by Chandra high-energy gratings

We present a detailed analysis of the soft X-ray emission of 3C445 using an archival Chandra HETG spectrum. Highly-ionized H- and He-like Mg, Si and S lines, as well as a resolved low-ionized Si K$α$ line, are detected in the high resolution spectrum. The He-like triplets of Mg and Si are resolved into individual lines, and the calculated R ratios indicate a high density for the emitter. The low values of the G ratios indicate the lines originate from collisionally ionized plasmas. However, the detection of a resolved narrow Ne X RRC feature in the spectrum seems to prefer to a photoionized environment. The spectrum is subsequently modelled with a photoionization model, and the results are compared with that of a collisional model. Through a detailed analysis on the spectrum, we exclude a collisional origin for these emission lines. A one-component photoionization model provides a great fit to the emission features. The best-fit parameters are log$ξ$ = $3.3^{+0.4}_{-0.3}$ erg cm s$^{-1}$, $n_{H}$ = $5^{+15}_{-4.5}\times10^{10}$ cm$^{-3}$ and $N_{H}$ = $2.5^{+3.8}_{-1.7}\times10^{20}$ cm$^{-2}$. According to the calculated high density for the emitter, the measured velocity widths of the emission lines and the inferred the radial distance (6 $\times$ $10^{14}$ - 8 $\times$ $10^{15}$ cm), we suggest the emission lines originating from matter locate in the broad line region (BLR).

astro-ph.GA↗

arXiv2006

Electron density diagnostic potential of Ar XIV soft X-ray emission lines

Theoretical electron density-sensitive line ratios $R_1 - R_6$ of Ar XIV soft X-ray emission lines are presented. We found that these line ratios are sensitive to electron density $n_e$, and the ratio $R_1$ is insensitive to electron temperature $T_e$. Recent work has shown that accurate atomic data, such as electron impact excitation rates, is very important for reliable determination of the electron density of laboratory and astrophysical plasmas. Present work indicates that the maximum discrepancy of line ratios introduced from different atomic data calculated with distorted wave and R-matrix approximations, is up to 18% in the range of $n_e=10^{9-13}$cm$^{-3}$. By comparison of these line ratios with experiment results carried out in electron beam ion trap (EBIT-II), electron density of the laboratory plasma is diagnosed, and a consistent result is obtained from $R_1$, $R_2$ and $R_3$. Our result is in agreement with that diagnosed by Chen et al using triplet of N VI. A relative higher diagnosed electron density from $R_2$ is due to its weak sensitivity to electron temperature. A better consistency at lower $T_e$ indicates that temperature of the laboratory plasma is lower than log$T_e$(K)=6.5. Comparison between the measured and theoretical ratios reveals that 32.014~Åline is weakly blended by lines from other Ar ions, while 30.344~Åline is strongly contaminated.

physics.plasm-ph↗