arXiv subjects

Liang-Duan Liu

Publications and source records attributed to Liang-Duan Liu.

58 records · Page 4Linked to original sources

arXiv2017

Afterglows and Macronovae Associated with Nearby Low-Luminosity Short-Duration Gamma-Ray Bursts

A binary neutron star (BNS) merger has been widely argued to be one of the progenitors of a short gamma-ray burst (SGRB). This central engine can be verified if its gravitational-wave (GW) event is detected simultaneously. Once confirmed, this kind of association will be a landmark in multi-messenger astronomy and will greatly enhance our understanding of the BNS merger processes. Due to the limited detection horizon of BNS mergers for the advanced LIGO/Virgo GW observatories, we are inclined to local SGRBs within few hundreds of mega-parsecs. Since normal SGRBs rarely fall into such a close range, to make it more observationally valuable, we have to focus on low-luminosity SGRBs which have a higher statistical occurrence rate and detection probability. However, there is a possibility that an observed low-luminosity SGRB is intrinsically powerful but we are off-axis and only observe its side emission. In this paper, we provide some theoretical predictions of both the off-axis afterglow emission from a nearby SGRB under the assumption of a structured jet and the macronova signal from the ejecta of this GW-detectable BNS merger. From the properties of the afterglow emission, we could distinguish an off-axis normal SGRB from an intrinsically low-energy quasi-isotropic class. Furthermore, with follow-up multi-wavelength observations, a few parameters for BNS mergers (e.g. the medium density and the ejecta mass and velocity) would be constrained.

astro-ph.HE↗

arXiv2017

A Multiple Ejecta-Circumstellar Meduim Interaction Model and Its Implications for the Superluminous Supernova iPTF15esb

Recently, a hydrogen-poor superluminous supernova (SLSN) iPTF15esb at redshift $z=0.224$ was reported, whose light curve (LC) and spectrum show several unusual characteristics. Its late-time spectrum shows a strong, broad H$α$ emission line and the bolometric LC exhibits two peaks and a post-peak plateau. Here we propose an ejecta-circumstellar medium (CSM) interaction model involving multiple shells and winds to explain this double-peak SN. We find that the theoretical LC reproduced by this model can well match the observations of iPTF15esb. Based on this result, we infer that the progenitor has undergone at least three violent mass-loss processes before the SN explosion. Furthermore, we find that the masses of the CSM wind and shells from the outermost shell (the first eruption) to the innermost wind (the final eruption) decrease sequentially but their densities increase. The variation trend of the inferred densities of the shells and wind is consistent with the stellar structure before an SN explosion. Further investigations for similar SLSNe would provide a probe for the mass-loss history of their progenitors.

astro-ph.HE↗

arXiv2017

A Monte Carlo Approach to Magnetar-powered Transients: I. Hydrogen-deficient Superluminous Supernovae

In this paper we collect 19 hydrogen-deficient superluminous supernovae (SLSNe) and fit their light curves, temperature evolution, and velocity evolution based on the magnetar-powered model. To obtain the best-fitting parameters, we incorporate the Markov Chain Monte Carlo approach. We get rather good fits for 7 events ($χ^2$/d.o.f = $0.24-0.96$) and good fits for other 7 events ($χ^2$/d.o.f = $1.37-3.13$). We find that the initial periods ($P_{0}$) and magnetic strength ($B_{p}$) of the magnetars supposed to power these SLSNe are in the range of $\sim 1.2-8.3$ ms and $\sim (0.2-8.8)\times 10^{14}\,$G, respectively; the inferred masses of the ejecta of these SLSNe are between 1 and 27.6 $M_{\odot }$, and the values of the gamma-ray opacity $κ_{γ}$ are between 0.01 and 0.82 cm$^2$ ~g$^{-1}$. We also calculate the fraction of the initial rotational energy of the magnetars harbored in the centers of the remnants of these SLSNe that is converted to the kinetic energy of the ejecta and find that the fraction is $\sim 19-97$ for different values of $P_{0}$ and $B_{p}$, indicating that the acceleration effect cannot be neglected. Moreover, we find that the initial kinetic energies of most of these SLSNe are so small ($\lesssim 2\times 10^{51}$ erg) that they can be easily explained by the neutrino-driven mechanism. These results can help clarify some important issues related to the energy-source mechanisms and explosion mechanisms and reveal the nature of SLSNe.

astro-ph.HE↗

arXiv2014

X-ray afterglow of GRB 050712: Multiple energy injections into the external shock

As indicated by the observed X-ray flares, a great amount of energy could be intermediately released from the postburst central engine of gamma-ray bursts (GRBs). As a natural consequence, the GRB external shock could be energized over and over. With such a multiple energy injection model, we explore the unique X-ray afterglow light curve of GRB 050712, which exists four apparent shallow decay plateaus. Together with three early X-ray flares, the central engine of GRB 050712 is supposed to release energy at least seven times after the burst. Furthermore we find that the energy released during four plateaus are all on the same order of magnitude, but the luminosity decreases with time significantly. These results may provide some interesting implications for the GRB central engine.

astro-ph.HE↗