Central Engine-Powered Bright X-ray Flares in Short Gamma-Ray Bursts: A Hint of Black Hole-Neutron Star Merger?

Authors: Hui-Jun Mu, Wei-Min Gu, Jirong Mao, Shu-Jin Hou, Da-Bin Lin, Tong Liu

Abstract: Short gamma-ray bursts may originate from the merger of double neutron stars (NS) or that of a black hole (BH) and an NS. We propose that the bright X-ray flare related to the central engine reactivity may hint a BH-NS merger, since such a merger can provide more fall-back materials and therefore a more massive accretion disk than the NS-NS merger. Based on the observed 49 short bursts with Swift/X-ray Telescope follow-up observations, we find that three bursts have bright X-ray flares, among which three flares from two bursts are probably related to the central engine reactivity...

Constraints on interquark interaction parameters with GW170817 in a binary strange star scenario

Authors: Enping Zhou, Xia Zhou, Ang Li

The LIGO/VIRGO detection of the gravitational waves from a binary merger system, GW170817, has put a clean and strong constraint on the tidal deformability of the merging objects. From this constraint, deep insights can be obtained in compact star equation of states, which has been one of the most puzzling problems for nuclear physicists and astrophysicists. Employing one of the most widely-used quark star EOS model, we characterize the star properties by the strange quark mass ($m_s$), an effective bag constant ($B_{\rm eff}$), the perturbative QCD correction ($a_4$), as well as the gap parameter ($\Delta$) when considering quark pairing, and investigate the dependences of the tidal deformablity on them...

Outflows from black hole hyperaccretion systems: short and long-short gamma-ray bursts and "quasi-supernovae"

Authors: Cui-Ying Song, Tong Liu, and Ang Li

The detections of some long gamma-ray bursts (LGRBs) relevant to mergers of neutron star (NS)-NS or black hole (BH)-NS, as well as some short gamma-ray bursts (SGRBs) probably produced by collapsars, muddle the boundary of two categories of gamma-ray bursts (GRBs). In both cases, a plausible candidate of central engine is a BH surrounded by a hyperaccretion disc with strong outflows, launching relativistic jets driven by Blandford-Znajek mechanism. In the framework of compact binary mergers, we test the applicability of the BH hyperaccretion inflow-outflow model on powering observed GRBs. We find that, for a low outflow ratio, ∼ 50%, postmerger hyperaccretion processes could power not only all SGRBs but also most of LGRBs

Effects of the nucleon radius on neutron stars in a quark mean field model

Authors: Zhen-Yu Zhu and Ang Li

Abstract: We study the effects of free space nucleon radius on nuclear matter and neutron stars within the framework of quark mean field model. The nucleon radius is treated self-consistently with this model, where quark confinement is adjusted to fit different values of nucleon radius. Corrections due to center-of-mass motion, quark-pion coupling, and one gluon exchange are included to obtain the nucleon mass in vacuum. The meson coupling constants that describe the behavior of many-body nucleonic system are newly-constructed by reproducing the empirical saturation properties of nuclear matter, including the recent determinations of symmetry energy parameters...

The Profiles of Fe Kα Line From the Inhomogeneous Accretion Flow

Authors: Xiao-Di Yu, Ren-Yi Ma, Ya-Ping Li, Hui Zhang, Tao-Tao Fang

Abstract: The clumpy disc, or inhomogeneous accretion flow, has been proposed to explain the properties of accreting black hole systems. However, the observational evidences remain to be explored. In this work, we calculate the profiles of Fe K{\alpha} lines emitted from the inhomogeneous accretion flow through the ray-tracing technique, in order to find possible observable signals of the clumps. Compared with the skewed double peaked profile of the continuous standard accretion disc, the lines show a multi-peak structure when the emissivity index is not very steep. The peaks and wings are affected by the position and size of the cold clumps...

Compact binary merger and kilonova: outflows from remnant disc

Authors: Tuan Yi, Wei-Min Gu, Tong Liu, Rajiv Kumar, Hui-Jun Mu, and Cui-Ying Song
Outflows launched from a remnant disc of compact binary merger may have essential contribution to the kilonova emission. Numerical calculations are conducted in this work to study the structure of accretion flows and outflows. By the incorporation of limited-energy advection in the hyper-accretion discs, outflows occur naturally from accretion flows due to imbalance between the viscous heating and the sum of the advective and radiative cooling...

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