arXiv subjects

Jin-Yuan Liao

Publications and source records attributed to Jin-Yuan Liao.

24 records · Page 2Linked to original sources

arXiv2019

Studies on the time response distribution of Insigh}-HXMT/LE

The Hard X-ray Modulation Telescope (HXMT) named Insight is China's first X-ray astronomical satellite. The Low Energy X-ray Telescope (LE) is one of its main payloads onboard. The detectors of LE adopt swept charge device CCD236 with L-shaped transfer electrodes. Charges in detection area are read out continuously along specific paths, which leads to a time response distribution of photons readout time. We designed a long exposure readout mode to measure the time response distribution. In this mode, CCD236 firstly performs exposure without readout, then all charges generated in preceding exposure phase are read out completely. Through analysis of the photons readout time in this mode, we obtained the probability distribution of photons readout time.

astro-ph.IM↗

arXiv2017

Disc-corona interaction in the heartbeat state of GRS 1915+105

Timing analysis provides information about the dynamics of matter accreting on to neutron stars and black holes, and hence is crucial for studying the physics of the accretion flow around these objects. It is difficult, however, to associate the different variability components with each of the spectral components of the accretion flow. We apply several new methods to two Rossi X-ray Timing Explorer observations of the black hole binary GRS 1915+105 during its heartbeat state to explore the origin of the X-ray variability and the interactions of the accretion-flow components. We offer a promising window into the disc--corona interaction through analysing the formation regions of the disc aperiodic variabilities with different time-scales via comparing the corresponding transition energies of the amplitude-ratio spectra. In a previous paper, we analysed the Fourier power density as a function of energy and frequency to study the origin of the aperiodic variability, and combined that analysis with the phase lag as a function of frequency to derive a picture of the disc--corona interaction in this source. We here, for the first time, investigate the phase lag as a function of energy and frequency, and display some interesting details of the disc--corona interaction. Besides, the results from the shape of amplitude-ratio spectrum and from several other aspects suggest that the quasi-periodic oscillation originates from the corona.

astro-ph.HE↗

arXiv2016

A timing view of the heartbeat state of GRS 1915+105

We present a timing analysis of two Rossi X-ray Timing Explorer observations of the microquasar GRS 1915+105 during the heartbeat state. The phase-frequency-power maps show that the intermediate-frequency aperiodic X-ray variability weakens as the source softens in the slow rise phase, and when the quasi-periodic oscillation disappears in the rise phase of the pulse of the double-peaked class its sub-harmonic is still present with a hard phase lag. In the slow rise phase, the energy-frequency-power maps show that most of the aperiodic variability is produced in the corona, and may also induce the aperiodic variability observed at low energies from an accretion disk, which is further supported by the soft phase lag especially in the intermediate-frequency range (with a time delay up to 20 ms). In the rise phase of the pulse, the low-frequency aperiodic variability is enhanced significantly and there is a prominent hard lag (with a time delay up to 50 ms), indicating that the variability is induced by extension of the disk toward small radii as implied by the increase in flux and propagates into the corona. However, during the hard pulse of the double-peaked class, the variability shows no significant lag, which may be attributed to an optically thick corona. These timing results are generally consistent with the spectral results presented by Neilsen et al. (2011, 2012) which indicated that the slow rise phase corresponds to a local Eddington limit and the rise phase of the pulse corresponds to a radiation pressure instability in the disk.

astro-ph.HE↗

arXiv2015

Primordial alignment of elliptical galaxies in intermediate redshift clusters

We measure primordial alignments for the red galaxies in the sample of eight massive galaxy clusters in the southern sky from the CLASH-VLT Large Programme, at a median redshift of 0.375. We find primordial alignment with about $3σ$ significance in the four dynamically young clusters, but null detection of primordial alignment in the four highly relaxed clusters. The observed primordial alignment is not dominated by any single one of the four dynamically young clusters, and is primarily due to a population of bright galaxies ($M_r<-20.5\ \rm{m}$) residing in the region 300 to 810 kpc from the cluster centers. For the first time, we point out that the combination of radial alignment and halo alignment can cause fake primordial alignment. Finally, we find that the detected alignment for the dynamically young clusters is real rather than fake primordial alignment.

astro-ph.GA↗

arXiv2015

Modeling the evolution and distribution of the frequency's second derivative and the braking index of pulsar spin

We model the evolution of the spin frequency's second derivative $\ddotν$ and the braking index $n$ of radio pulsars with simulations within the phenomenological model of their surface magnetic field evolution, which contains a long-term power-law decay modulated by short-term oscillations. For the pulsar PSR B0329+54, a model with three oscillation components can reproduce its $\ddotν$ variation. We show that the "averaged" $n$ is different from the instantaneous $n$, and its oscillation magnitude decreases abruptly as the time span increases, due to the "averaging" effect. The simulated timing residuals agree with the main features of the reported data. Our model predicts that the averaged $\ddotν$ of PSR B0329+54 will start to decrease rapidly with newer data beyond those used in Hobbs et al.. We further perform Monte Carlo simulations for the distribution of the reported data in $|\ddotν|$ and $|n|$ versus characteristic age $τ_{\rm c}$ diagrams. It is found that the magnetic field oscillation model with decay index $α=0$ can reproduce the distributions quite well. Compared with magnetic field decay due to the ambipolar diffusion ($α=0.5$) and the Hall cascade ($α=1.0$), the model with no long term decay ($α=0$) is clearly preferred for old pulsars by the p-values of the two-dimensional Kolmogorov-Smirnov test.

astro-ph.HE↗

arXiv2013

Wavelength Measurements of K Transitions of Oxygen, Neon, and Magnesium with X-ray Absorption Lines

Accurate atomic transition data are important in many astronomical research areas especially in line spectroscopy study. Whereas transition data of He-like and H-like ions (i.e., ions at high-charge states) are accurately calculated, that of K transitions of neutral or low-ionized metal elements are still very uncertain. Spectroscopy of absorption lines produced in the interstellar medium (ISM) has been proven to be an effective way to measure the central wavelengths of these atomic transitions. In this work we analyze 36 Chandra High Energy Transmission Grating observations and search for and measure the ISM absorption lines along sight lines of 11 low-mass X-ray binaries. We correct the Galactic rotation velocity to the rest frame for every observation and then use two different methods to merge all the corrected spectra to a co-added spectrum. However the co-added spectra obtained by these methods exhibit biases, either to the observations of high counts or high signal-to-noise ratios of the lines. We make Bayesian analysis to several significantly detected lines to obtain the systematic uncertainty and the bias correction of other lines. Compared to previous studies (e.g., Yao et al. 2009), our results improve the accuracy of wavelengths by a factor from two to five and significantly reduce the systematic uncertainties and biases. Several weak transitions (e.g., 1s--2p of Mg IV and Mg V; 1s--3p of Mg III and Mg V) are also detected for the first time, albeit with low significance; future observations with improved accuracy are required to confirm these detections.

astro-ph.HE↗