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Gao H.,Beijing Normal University | Zhang B.,University of Nevada, Las Vegas | Zhang B.,Peking University | Lu H.-J.,Guangxi University | And 2 more authors.
Astrophysical Journal | Year: 2017

The merger of a double neutron star (NS-NS) binary may result in a rapidly rotating massive NS with an extremely strong magnetic field (i.e., a millisecond magnetar). In this case, the magnetic spin-down of the NS remnant provides an additional source of sustained energy injection, which would continuously power the merger ejecta. The thermal emission from the merger ejecta would give rise to a bright optical "magnetar-powered merger-nova." In this work, we carry out a complete search for magnetar-powered merger-nova from a Swift short gamma-ray burst sample. We focus on short GRBs with extended emission or internal plateau, which may signify the presence of magnetars as the central engine. We eventually find three candidates of magnetar-powered merger-nova from the late observations of GRB 050724, GRB 070714B, and GRB 061006. With standard parameter values, the magnetar remnant scenario could well interpret the multi-band data of all three bursts, including the extended emission and their late chromatic features in the optical and X-ray data. The peak luminosities of these merger-novae reach several times , more than one order of magnitude brighter than the traditional "kilo-novae" with peak luminosity of . Intense, multi-color, late-time observations of short GRBs are encouraged to identify more merger-novae in the future. © 2017. The American Astronomical Society. All rights reserved..

Lu H.-J.,Guangxi University | Lu H.-J.,Guangxi Key Laboratory for Relativistic Astrophysics | Zhang H.-M.,Guangxi University | Zhang H.-M.,Guangxi Key Laboratory for Relativistic Astrophysics | And 7 more authors.
Astrophysical Journal | Year: 2017

GRB 160821B is a short gamma-ray burst (SGRB) at redshift z = 0.16, with a duration less than 1 s and without any "extended emission" detected up to more than 100 s in both Swift/BAT and Fermi/GBM bands. An X-ray plateau with a sharp drop 180 s after the BAT trigger was observed with Swift/XRT. No supernova or kilo-nova signature was detected. Assuming the central engine of this SGRB is a recently born supra-massive magnetar, we can explain the SGRB as jet radiation and its X-ray plateau as the internal energy dissipation of the pulsar wind as it spins down. We constrain its surface magnetic field to Bp < 3.12 ×1016 G and initial spin period to P0 < 8.5 ×10-3 s. Its equation of state is consistent with the GM1 model with MTOV ∼ 2.37 Mo and ellipticity < 0.07. Its gravitational wave (GW) radiation may be detectable with the future Einstein Telescope, but is much weaker than the current detectability limit of Advanced LIGO. The GW radiation of such an event would be detectable by Advanced LIGO if it occurred at a distance of 100 Mpc (z = 0.023). © 2017. The American Astronomical Society. All rights reserved..

Lin T.,Guangxi University | Lin T.,Guangxi Key Laboratory for Relativistic Astrophysics | Qiu Z.R.,Sun Yat Sen University | Yang J.-R.,National Taiwan University | And 4 more authors.
Materials Letters | Year: 2016

This paper reports the transient photoluminescence properties of a typical InGaN/GaN multiple quantum well light emitting diode structure. Two decay processes were found to contribute to the photoluminescence dynamics. Based on the exciton localization model, key factors, transient lifetimes of radiative/nonradiative recombination, were obtained respectively for two decay processes by numerically fitting and separating the mixed photoluminescence efficiencies and photoluminescence decay data, which provide guidance to trace the origins of exciton localization. The origins of slow PL process and fast PL process were reasonably assigned to local compositional fluctuations of indium and thickness variation of InGaN layers, respectively. © 2016 Elsevier B.V. All rights reserved.

Wang Y.-Z.,Guangxi University | Wang Y.-Z.,Guangxi Key Laboratory for Relativistic Astrophysics | Zhao Y.,University of Florida | Shao L.,Hebei Normal University | And 5 more authors.
Astrophysical Journal | Year: 2016

Strong spectral softening has been revealed in the late X-ray afterglows of some gamma-ray bursts (GRBs). The scenario of X-ray scattering around the circumburst dusty medium has been supported by previous works due to its overall successful prediction of both the temporal and spectral evolution of some X-ray afterglows. To further investigate the observed feature of spectral softening we now systematically search the X-ray afterglows detected by the X-ray telescope aboard Swift and collect 12 GRBs with significant late-time spectral softening. We find that dust scattering could be the dominant radiative mechanism for these X-ray afterglows regarding their temporal and spectral features. For some well-observed bursts with high-quality data, the time-resolved spectra could be well-produced within the scattering scenario by taking into account the X-ray absorption from the circumburst medium. We also find that during spectral softening the power-law index in the high-energy end of the spectra does not vary much. The spectral softening is mainly manifested by the spectral peak energy continually moving to the soft end. © 2016. The American Astronomical Society. All rights reserved.

Liang E.-W.,Guangxi University | Liang E.-W.,Guangxi Key Laboratory for Relativistic Astrophysics | Liang E.-W.,CAS National Astronomical Observatories | Lin T.-T.,Guangxi University | And 9 more authors.
Astrophysical Journal | Year: 2015

We select a sample of 34 gamma-ray bursts (GRBs) whose Γ0 values are derived with the onset peaks observed in the afterglow light curves (except for GRB 060218, whose Γ0 is estimated with its radio data), and investigate the correlations among Γ0, the isotropic peak luminosity (Liso), and the peak energy (Ep,z) of the νfν spectrum in the cosmological rest frame. An analysis of pair correlations among these observables well confirms the results reported by the previous papers. More interestingly, a tight correlation among Liso, Ep,z, and Γ0 is found from a multiple regression analysis, which takes the form of Liso ∝ Ep,z 1.34 ± 0.14 Γ0 1.32± 0.19 or Ep,z ∝ Liso 0.55 ± 0.06 Γ0 -0.50± 0.17 Nine other GRBs whose Γ0 are derived via the pair production opacity constraint also follow such a correlation. Excluding GRB 060218, the Liso-Ep,z-Γ0 correlation is valid, and it even holds in the jet co-moving frame. However, GRB 060218 deviates the Liso'-Ep' relation of typical GRBs in the jet co-moving frame with 3σ. We argue that the Liso-Ep,z-Γ0 correlation may be more physical than the Liso-Ep,z correlation, since physically the relationship between the observed Liso and Ep,z not only depends on radiation physics, but also depends on the bulk motion of the jet. We explore the possible origins of this correlation and discuss its physical implications for understanding GRB jet composition and radiation mechanisms. © 2015. The American Astronomical Society. All rights reserved.

Du S.,Guangxi University | Du S.,Guangxi Key Laboratory for Relativistic Astrophysics | Lu H.-J.,Guangxi University | Lu H.-J.,Guangxi Key Laboratory for Relativistic Astrophysics | And 5 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

A rapidly spinning, strongly magnetized neutron star (NS) is invoked as the central engine for some gamma-ray bursts (GRBs), especially, the 'internal plateau' feature of X-ray afterglow. However, for these 'internal plateau' GRBs, how to produce their prompt emission remains an open question. Two different physical processes have been proposed in the literature, (1) a new-born NS is surrounded by a hyper-accreting and neutrino cooling disc, the GRB jet can be powered by neutrino annihilation aligning the spin axis; (2) a differentially rotating millisecond pulsar was formed due to different angular velocity between the interior core and outer shell parts of the NS, which can power an episodic GRB jet. In this paper, by analysing the data of one peculiar GRB 070110 (with internal plateau), we try to test which model is being favoured. By deriving the physical parameters of magnetar with observational data, the parameter regime for initial period (P0) and surface polar cap magnetic field (Bp) of the central NS are 0.96 ~ 1.2ms and (2.4 ~ 3.7) × 1014 G, respectively. The radiative efficiency of prompt emission is about ηγ ~ 6 per cent. However, the radiative efficiency of internal plateau (ηX) is larger than 31 per cent assuming the MNS ~ 1.4M⊙ and P0 ~ 1.2ms. The clear difference between the radiation efficiencies of prompt emission and internal plateau implies that they maybe originated from different components (e.g. prompt emission from the relativistic jet powered by neutrino annihilation, while the internal plateau from the magnetic outflow wind). © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Jiang W.,Guangxi University | Jiang W.,Guangxi Key Laboratory for Relativistic Astrophysics | Guo J.,Guangxi University | Cao S.,Guangxi University
Russian Journal of Electrochemistry | Year: 2016

La1.8Ti0.2MgNi9–xCox (x = 0, 0.1, 0.3, 0.5) alloys were prepared by magnetic levitation melting under argon atmosphere. The effects of Co substitution on the phase structure and the hydrogen storage properties of the alloys were investigated. The results show that LaNi5 and LaMg2Ni9 phases are contained in all experimental alloys. LaNi3 phase disappears and LaNi2 phase appears as x ≥ 0.1 and x ≥ 0.3, respectively. Electrochemical performances have been improved after Co substitution for Ni, for example, the discharge capacity and the high rate dischargeability (HRD) reach the maximum at x = 0.1, and the optimum cycling stability is obtained at x = 0.5. The positive impact of Co on the hydrogen diffusion rate in bulk enhances the HRD, but to high Co content (x ≥ 0.3), the unsatisfied hydrogen desorption capability brings relative low HRD compared with the alloy electrode at x = 0.1. © 2016, Pleiades Publishing, Ltd.

Lu J.,Guangxi University | Lu J.,Guangxi Key Laboratory for Relativistic Astrophysics | Xing J.-W.,Huazhong University of Science and Technology | Zou Y.-C.,Huazhong University of Science and Technology | And 3 more authors.
Research in Astronomy and Astrophysics | Year: 2015

The well-known correlation between radio luminosity (LR) and X-ray luminosity (LX), LR/LX ≃ 10-5, holds for a variety of objects, such as active galactic nuclei, Galactic black holes, solar flares and cool stars. Here we extend the relation to gamma-ray bursts (GRBs) and find that the GRBs also obey a similar LR - LX relation, with a slightly different slope of LR ∝ LX1.1. This relation implies that the explosions that occur on different scales may have a common underlying origin. © 2015 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd.

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