arXiv subjects

Xiongwei Liu

Publications and source records attributed to Xiongwei Liu.

5 recordsLinked to original sources

arXiv2026

Studies on the dark sector interaction from joint analysis of cosmological probes

We test whether constraints on the nonlinear interaction $\xi$IDE are stable under different treatments of the Type Ia supernovae absolute calibration. \textit{Fermi} GRBs measurements and the Amati-relation parameters are fitted jointly with PantheonPlus SNe Ia, DESI DR2 BAO, and an updated cosmic-chronometer compilation. We compare the PantheonPlus-SH0ES route, which retains the SN absolute calibration, with the PantheonPlus-only route, in which the SN absolute magnitude is analytically marginalized. The GOLD GRB sample is adopted for the main analysis, while the FULL GRB sample is used to assess sample dependence. For the interaction parameter $\gamma\equiv\xi+3w$, where $\gamma=0$ denotes the non-interacting limit, the GOLD sample gives $\gamma=1.453^{+1.297}_{-1.597}$ for the PantheonPlus-SH0ES and $\gamma=-0.634^{+1.668}_{-2.486}$ for the PantheonPlus-only. Although the posterior medians correspond to opposite directions of energy transfer, neither route excludes $\gamma=0$ at 68\% credibility, and the reconstructed interaction rate remains consistent with zero over the redshift range considered. Replacing the GOLD sample with the FULL sample produces negligible changes in the interaction constraints. Moreover, $w$CDM and CPL achieve likelihood improvements comparable to that of $\xi$IDE, while the information criteria do not consistently favor the interacting model. A redshift-bin diagnostic finds no significant redshift evolution of the Amati relation. We find no compelling evidence for a dark sector interaction that is robust to the choice of SN calibration or specifically favored over noninteracting dark energy extensions.

astro-ph.CO↗

arXiv2026

Interacting dark energy constraints from Fermi GRBs and Pantheon+ SNe Ia with full GRB covariance

The standard $\Lambda$CDM model faces long-standing theoretical and observational problems, such as the Hubble tension, which motivate extensions beyond $\Lambda$CDM, including interacting dark energy (IDE). Type Ia supernovae (SNe Ia) are precise probes of the late-time expansion history, while gamma-ray bursts (GRBs) can extend distance measurements to higher redshifts. However, GRB cosmology depends on the calibration of luminosity relations, the covariance treatment, and the intrinsic scatter. In this work, we use 15 years of Fermi/GBM long-GRB observations and Pantheon+ SNe Ia to test whether current distance data provide evidence in favor of IDE models over $\Lambda$CDM. We compare four flat models: $\Lambda$CDM, $w$CDM, IDE-$\rho_{\rm de}$, and IDE-$\rho_{\rm c}$. The GRB covariance is constructed by propagating the Amati-relation calibration covariance, and the GRB intrinsic scatter is sampled as a nuisance parameter. A diagonal GRB covariance is also considered as a robustness test. With the full GRB covariance, both the GOLD and FULL samples give $H_0\simeq 72.8~{\rm km~s^{-1}~Mpc^{-1}}$ in $\Lambda$CDM. The IDE models do not improve the fit enough to compensate for their extra parameters, and the BIC favors the simpler $\Lambda$CDM model. The diagonal-covariance test gives the same model-selection conclusion, although it changes the fitted GRB intrinsic scatter. We conclude that, for the two interaction forms considered here and at the present level of GRB systematics, current GRB and Pantheon+ data do not provide evidence for interacting dark energy. Current GRBs mainly provide a high-redshift extension of the Hubble diagram and test the shape of the expansion history.

astro-ph.CO↗

arXiv2017

Calvera: A low-mass strangeon star torqued by debris disk?

Calvera is a $59\,\mathrm{ms}$ isolated pulsar, being unique due to its non-detection in radio, optical and gamma-rays but the purely thermal emission in soft X-rays. It is suggested that Calvera could be an ordinary middle-aged pulsar with significant magnetospheric activity at a large distance. Alternatively, it is proposed in this paper that Calvera is a low-mass strangeon star with inactive magnetosphere (dead). In this scenario, we jointly fit the spectra obtained by the {\it XMM-Newton} Observatory and the {\it Chandra} X-ray Observatory with the strangeon star atmosphere model. The spectral model is successful in explaining the radiation properties of Calvera and X-ray Dim Isolated Neutron Stars, both showing similar observation features. Within the dead pulsar picture, Calvera might be of high temperature at $0.67\,\mathrm{keV}$, possessing a small stellar radius $R\la4\,\mathrm{km}$ and a presumably small magnetic field $B\la10^{11}\,\mathrm{G}$ and is probably braked by the fall-back disk accretion. Future advanced facilities may provide unique opportunities to know the real nature of Calvera.

astro-ph.HE↗

arXiv2012

AXPs & SGRs: Magnetar or Quarctar?

The concept of a "magnetar" was proposed mainly because of two factors. First, the X-ray luminosity of Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) is larger than the rotational energy loss rate, and second, the magnetic field strength calculated from "normal method" is super strong. It is proposed that the radiation energy of magnetar comes from its magnetic fields. Here it is argued that the magnetic field strength calculated through the normal method is incorrect when X-ray luminosity is larger than rotational energy loss rate, because the wind braking is not taken into account. Besides, the "anti-magnetar" and some other X-ray and radio observations are difficult to understand with a magnetar model. Instead of the magnetar, we propose a "quarctar", which is a crusted quark star in an accretion disk, to explain the observations. In this model, the persistent X-ray emission, burst luminosity, spectrum of AXPs and SGRs can be understood naturally. The radio-emitting AXPs, which are challenging the magnetar, can also be explained by the quarctar model.

astro-ph.HE↗

arXiv2010

Particle Emission-dependent Timing Noise of Pulsars?

Though pulsars spin regularly, the differences between the observed and predicted ToA (time of arrival), known as "timing noise", can still reach a few milliseconds or more. We try to understand the noise in this paper. As proposed by Xu & Qiao in 2001, both dipole radiation and particle emission would result in pulsar braking. Accordingly, possible fluctuation of particle current flow is suggested here to contribute significant ToA variation of pulsars. We find that the particle emission fluctuation could lead to timing noise which can't be eliminated in timing process, and that a longer period fluctuation would arouse a stronger noise. The simulated timing noise profile and amplitude are in accord with the observed timing behaviors on the timescale of years.

astro-ph.HE↗