Jieru Wang

Constraining broad-line regions from time lags of broad emission lines relative to radio emission

In this paper, a new method is proposed to estimate the broad-line region sizes of ultraviolet (UV) lines RuvBLR. It is applied to 3C 273. First, we derive the time lags of radio emission relative to broad emission lines Lya and C iv by the z-transformed discrete correlation function (ZDCF) method. The broad lines lag the 5-, 8-, 15-, 22- and 37-GHz emission. The measured lags tuvob are of the order of years. For a given line, tuvob decreases as the radio frequency increases. This trend results from the radiative cooling of relativistic electrons. Both UV lines have a lag of tuvob=-2.74+0.06- 0.25 yr relative to the 37-GHz emission. These results are consistent with those derived from the Balmer lines in Paper I. Secondly, we derive the time lags of the lines Lya, C iv, H, H beta and Ha relative to the 37-GHz emission by the flux randomization/random subset selection (FR/RSS) Monte Carlo method. The measured lags are tob=-3.40+0.31- 0.05, -3.40+0.41- 0.14, -2.06+0.36- 0.92, -3.40+1.15- 0.20 and -3.56+0.35- 0.18 yr for the lines Lya, C iv, H, H beta and Ha, respectively. These estimated lags are consistent with those derived by the ZDCF method within the uncertainties. Based on the new method, we derive RuvBLR= 2.54+0.71- 0.35 to 4.01+0.90- 1.16 and 2.54+0.80- 0.43 to 4.01+0.98- 1.24 light-years for the Lya and C iv lines, respectively. Considering the uncertainties, these estimated sizes are consistent with those obtained in the classical reverberation mapping for the UV and the Balmer lines. This indicates that their emitting regions are not separated so large as in the classical mapping of the UV and optical lines. These results seem to depart from the stratified ionization structures obtained in the classical mapping.

Wide-band profile domain pulsar timing analysis

We extend profile domain pulsar timing to incorporate wide-band effects such as frequency-dependent profile evolution and broad-band shape variation in the pulse profile. We also incorporate models for temporal variations in both pulse width and in the separation in phase of the main pulse and interpulse. We perform the analysis with both nested sampling and Hamiltonian Monte Carlo methods. In the latter case, we introduce a new parametrization of the posterior that is extremely efficient in the low signal-to-noise regime and can be readily applied to a wide range of scientific problems. We apply this methodology to a series of simulations, and to between seven and nine years of observations for PSRs J1713+0747, J1744−1134 and J1909−3744 with frequency coverage that spans 700–3600 Mhz. We use a smooth model for profile evolution across the full frequency range, and compare smooth and piecewise models for the temporal variations in dispersion measure (DM). We find that the profile domain framework consistently results in improved timing precision compared to the standard analysis paradigm by as much as 40 per cent for timing parameters. Incorporating smoothness in the DM variations into the model further improves timing precision by as much as 30 per cent. For PSR J1713+0747, we also detect pulse shape variation uncorrelated between epochs, which we attribute to variation intrinsic to the pulsar at a level consistent with previously published analyses. Not accounting for this shape variation biases the measured arrival times at the level of ∼30 ns, the same order of magnitude as the expected shift due to gravitational waves in the pulsar timing band.

Uranium sorption from saline lake brine by amidoximated silica

A series of silica sorbents with different content of amidoxime groups were prepared through co-condensation method and applied to extract uranium from saline lake brine. The optimum amidoxime group content was determined and effects of pH on uranium sorption were investigated. Sorption kinetic and isotherms were also investigated. XPS analysis indicated that the adsorption mechanism of uranium was attributed to the interaction between uranyl ion and N in the amidoxime. Amidoximated silica could efficiently absorb the naturally occurring uranium in the saline lake brine samples from Qinghai, China.

Solvent extraction of americium(III) and europium(III) with tridentate N,N-dialkyl-1,10-phenanthroline-2-amide-derived ligands: extraction, complexation and theoretical study

The extraction and complexation behavior of soft–hard combined N,N-dialkyl-1,10-phenanthroline-2-amide (PTA) ligands with Am(III) and Eu(III) in HNO3 solution was investigated. The effects of acidity of the aqueous solution, shaking time, concentration of the extractant and temperature on the distribution ratios were studied. The extraction ability for both Am(III) and Eu(III) was found to decrease with an increase in the length of the substituent alkyl chains, and the highest extractability and selectivity for Am(III) over Eu(III) were found for the diethyl-substituted ligand. The separation factor for Am(III) over Eu(III) reached around 7.6 at low acidity and high salinity. UV-vis titrations revealed that the dialkyl-substituted tridentate PTAs all predominantly formed 1 : 1 complexes with Eu(III), which agreed well with the results of slope analyses in the extraction experiments. The stability constants (KEuL) as well as the protonation constants (KH) were also determined by UV-vis titration. Computational chemistry gave a good explanation of the relationship between the alkalinity and the protonation energy of the proposed PTA ligands. Density functional theory (DFT) calculations on the optimized structures of Am(III) and Eu(III) complexes with C2-PTA showed that the selectivity may originate from differences in the degree of covalency of the bonds between the metal ions and the donor N atoms, which fits well with the experimental results.

The shallow-decay phase in both the optical and X-ray afterglows of Swift GRB 090529A: energy injection into a wind-type medium?

The energy injection model is the usual choice for interpreting the shallow-decay phase in Swift gamma-ray burst (GRB) X-ray afterglows. However, very few GRBs have simultaneous signatures of energy injection in their optical and X-ray afterglows. Here, we report on the optical observations of GRB 090529A from 2000 s to ∼10 6 s after the burst, in which an achromatic decay is seen at both wavelengths. The optical light curve shows a decay from 0.37 to 0.99, with a break at ∼10 5 s. In the same time interval, the decay indices of the X-ray light curve changed from 0.04 to 1.2. Comparing these values with the closure relations, the segment after 3 × 10 4 s is consistent with the prediction of the forward shock in an interstellar medium without any energy injection. The shallow-decay phase between 2000 and 3 × 10 4 s could be a result of the external shock in a wind-type medium with an energy injection under the condition of νo <ν c <ν x. However, the constraint of the spectral region is not consistent with the multiband observations. For this shallow-decay phase, other models are also possible, such as energy injection with evolving microphysical parameters, a jet viewed off-axis, etc.

INTEGRAL and Swift/XRT observations of IGR J18179−1621

IGR J18179-1621 is a hard X-ray binary transient discovered recently by INTEGRAL. Here we report on detailed timing and spectral analysis of IGR J18179-1621 in X-rays based on available INTEGRAL and Swift data. From the INTEGRAL analysis, IGR J18179-1621 is detected with a significance of 21.6s in the 1840 keV band by ISGRI and 15.3s in the 325 keV band by JEM-X, between 2012 February 29 and 2012 March 1. We analyse two quasi-simultaneous Swift ToO observations. A clear 11.82-s pulsation is detected above the white noise at a confidence level larger than 99.99 per cent. The pulse fraction is estimated as 22 +/- 8 per cent at 0.210 keV. No sign of pulsation is detected by INTEGRAL/ISGRI in the 1840 keV band. With Swift and INTEGRAL spectra combined in soft and hard X-rays, IGR J18179-1621 could be fitted by an absorbed power law with a high-energy cut-off plus a Gaussian absorption line centred at 21.5 keV. An additional absorption intrinsic to the source is found, while the absorption line is evidence for a most probable origin from cyclotron resonant scattering and suggests a magnetic field in the emitting region of 2.4 x 1012 G.

Hints of Correlation between Broad-line and Radio Variations for 3C 120

In this paper, we investigate the correlation between broad-line and radio variations for the broad-line radio galaxy 3C 120. By the z-transformed discrete correlation function method and the model-independent flux randomization/random subset selection (FR/RSS) Monte Carlo method, we find that broad H beta line variations lead the 15 GHz variations. The FR/RSS method shows that the H beta line variations lead the radio variations by a factor of tau(ob) = 0.34 +/- 0.01 yr. This time lag can be used to locate the position of the emitting region of radio outbursts in the jet, on the order of similar to 5 lt-yr from the central engine. This distance is much larger than the size of the broad-line region. The large separation of the radio outburst emitting region from the broad-line region will observably influence the gamma-ray emission in 3C 120.