arXiv subjects

Xiang-Hua Li

Publications and source records attributed to Xiang-Hua Li.

5 recordsLinked to original sources

arXiv2026

Timing and Spectral Studies of PSR J2022+3842 with NICER and NuSTAR

We report on the long-term timing analysis of PSR J2022+3842 using observations from the Neutron Star Interior Composition Explorer (NICER), along with spectral properties derived from joint observations with NICER and the Nuclear Spectroscopic Telescope Array (NuSTAR). Two large glitches are identified around MJD 58335 with $Δν=25.35(2)\times10^{-6}$ Hz and MJD 58875 with $Δν=52.078(6)\times10^{-6}$ Hz. Furthermore, phase-resolved spectroscopy reveals that the X-ray emission is well described by a power-law model across different phase intervals. The phase-integrated X-ray spectrum (1-79 keV) has a photon index of $Γ=1.22(7)$, yielding an unabsorbed 0.5-10 keV flux of $8.9(6)\times10^{-13}$ erg cm$^{-2}$ s$^{-1}$. The main pulse spectrum (1.2-79 keV) and the inter-pulse spectrum (1-70 keV) are harder with $Γ=1.17(4)$ and $Γ=1.03^{+0.07}_{-0.06}$ separately, producing an unabsorbed 0.5-10 keV flux of $33.2(2)\times10^{-13}$ erg cm$^{-2}$ s$^{-1}$ and $29(3)\times10^{-13}$ erg cm$^{-2}$ s$^{-1}$. Investigation of the pulse profile evolution with time shows that no significant variations were observed.

astro-ph.HE↗

arXiv2026

An Insight-HXMT View of the Evolution of the Type-C Quasiperiodic Oscillation during the Flaring State of Swift J1727.8-1613

We present a detailed analysis of the evolution of type-C quasiperiodic oscillations (QPOs) observed during the flaring state of the recently discovered black hole X-ray binary Swift J1727.8-1613, utilizing data from the Insight Hard X-ray Modulation Telescope. By examining the relation between the QPO fractional rms amplitude and QPO frequency across various energy bands, we discover that the behavior significantly differs between these energy bands. Below 10 keV, the QPO fractional rms generally decreases with increasing QPO frequency, whereas above 10 keV, the QPO fractional rms remains relatively stable with frequency. Additionally, we report, for the first time, the detection of a common break at around 4 Hz in the relation between QPO fractional rms and frequency in both the 2-4 and 50-100 keV energy bands. We also find that the evolution of all the spectral parameters alters its behavior at around 4 Hz, with the changes in all parameters becoming flatter. This suggests a significant change in the geometry of the accretion flow. We attribute the observed break to the overall changes in the spectrum.

astro-ph.HE↗

arXiv2025

PSR J1838-0655: X-Ray Observations with NICER and NuSTAR

We report on the timing and spectral properties of PSR J1838-0655 using joint observations from the Neutron Star Interior Composition Explorer (NICER) and the Nuclear Spectroscopic Telescope Array (NuSTAR). By disentangling the pulsar's emission from its surrounding wind nebula across joint Chandra, NuSTAR, and NICER observations, we find the pulsar's broad-band X-ray spectrum (1.3--79\,keV) is best-described by a broken power-law model. The model features photon indices of $Γ_1 = 1.19 \pm 0.07$ and $Γ_2 = 1.47 \pm 0.02$ below and above a break energy of $E_{\rm b} = 7.7 \pm 0.8$\,keV. The resulting unabsorbed 2--10\,keV flux from the pulsar is $(9.5^{+0.4}_{-0.3}) \times 10^{-12}~\mathrm{erg\,cm^{-2}\,s^{-1}}$. Furthermore, timing analysis of NICER data spanning MJD 58250 to 60630 reveals a very large glitch occurring around MJD 59300, characterized by a frequency jump of $Δν= 29.367(7) \times 10^{-6}$ Hz, which can be well explained by the vortex creep model. Phase-resolved spectral analysis indicates a clear anti-correlation between the photon index and the pulse intensity, suggesting spectral hardening at the pulse peak.

astro-ph.HE↗

arXiv2023

The year-scale X-ray variations in the core of M87

The analysis of light variation of M87 can help us understand the disc evolution. In the past decade, M87 has experienced several short-term light variabilities related to flares. We also find there are year-scale X-ray variations in the core of M87. Their light variability properties are similar to clumpy-ADAF. By re-analyzing 56 $\it Chandra$ observations from 2007 to 2019, we distinguish the `non-flaring state' from `flaring state' in the light variability. After removing flaring state data, we identify 4 gas clumps in the nucleus and all of them can be well fitted by the clumpy-ADAF model. The average mass accretion rate is $\sim 0.16 \rm M_{\odot} yr^{-1}$. We analyze the photon index($Γ$)-flux(2-10keV) correlation between the non-flaring state and flaring state. For the non-flaring states, the flux is inversely proportional to the photon index. For the flaring states, we find no obvious correlation between the two parameters. In addition, we find that the flare always occurs at a high mass accretion rate, and after the luminosity of the flare reaches the peak, it will be accompanied by a sudden decrease in luminosity. Our results can be explained as that the energy released by magnetic reconnection destroys the structure of the accretion disc, thus the luminosity decreases rapidly and returns to normal levels thereafter.

astro-ph.HE↗

arXiv2008

Non-Thermal X-ray Properties of Rotation Powered Pulsars and Their Wind Nebulae

We present a statistical study of the non-thermal X-ray emission of 27 young rotation powered pulsars (RPPs) and 24 pulsar wind nebulae (PWNe) by using the Chandra and the XMM-Newton observations, which with the high spatial resolutions enable us to spatially resolve pulsars from their surrounding PWNe. We obtain the X-ray luminosities and spectra separately for RPPs and PWNe, and then investigate their distribution and relation to each other as well as the relation with the pulsar rotational parameters. In the pair-correlation analysis we find that: (1) the X-ray (2-10 keV) luminosities of both pulsar and PWN (L_{psr} and L_{pwn}) display a strong correlation with pulsar spin down power Edot and characteristic age, and the scalings resulting from a simple linear fit to the data are L_{psr} \propto Edot^{0.92 \pm 0.04} and L_{pwn} \propto Edot^{1.45 \pm 0.08} (68% confidence level), respectively, however, both the fits are not statistically acceptable; (2) L_{psr} also shows a possible weak correlation with pulsar period P and period derivative Pdot, whereas L_{pwn} manifests a similar weak correlation with Pdot only; (3) The PWN photon index Gamma_{pwn} is positively correlated with L_{pwn} and L_{pwn}/Edot. We also found that the PWN X-ray luminosity is typically 1 to 10 times larger than that from the underlying pulsar, and the PWN photon indices span a range of ~1.5 to ~2. The statistic study of PWN spectral properties supports the particle wind model in which the X-ray emitting electrons are accelerated by the termination shock of the wind.

astro-ph↗