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Gong H.,Nanjing University | Gong H.,Bengbu College | Ruan X.-X.,Jiangsu University | Pang H.-R.,Nanjing Southeast University | And 2 more authors.
Modern Physics Letters B | Year: 2015

In this paper, taking into account the effect of the induced interaction, we calculate the energy of ultracold Fermi gases at unitarity in the framework of non-self-consistent T-matrix approximation (nTMA) above the critical temperature and compare the result with the experimental data and other theoretical calculation without induced interaction. Our calculated chemical potential is higher than the experimental data, but our calculated energy obtains a good agreement with Tokyo experiment for temperature range between 0.6TF and 0.8TF. © 2015 World Scientific Publishing Company.

Yuan Q.,CAS Institute of High Energy Physics | Yuan Q.,University of Nevada, Las Vegas | Yin P.-F.,CAS Institute of High Energy Physics | Wu X.-F.,University of Nevada, Las Vegas | And 5 more authors.
Astrophysical Journal Letters | Year: 2011

A statistical scenario is proposed to explain the γ-ray variability and flares of the Crab Nebula, which were observed recently by the Fermi/LAT. In this scenario electrons are accelerated in a series of knots, whose sizes follow a power-law distribution. These knots presumably move outward from the pulsar and have a distribution in the Doppler boost factor. The maximal electron energy is assumed to be proportional to the size of the knot. Fluctuations at the highest energy end of the overall electron distribution will result in variable γ-ray emission via the synchrotron process in the ∼100MeV range. Since highly boosted larger knots are rarer than smaller knots, the model predicts that the variability of the synchrotron emission increases with the photon energy. We realize such a scenario with a Monte Carlo simulation and find that the model can reproduce both the two γ-ray flares over a period of 1 year and the monthly scale γ-ray flux fluctuations as observed by the Fermi/LAT. The observed γ-ray spectra in both the steady and flaring states are also well reproduced. © 2011. The American Astronomical Society. All rights reserved.

Liu X.-W.,University of Sichuan | Wu X.-F.,Chinese Academy of Sciences | Wu X.-F.,Joint Center for Particle Nuclear Physics and Cosmology | Lu T.,Chinese Academy of Sciences | Lu T.,Joint Center for Particle Nuclear Physics and Cosmology
Astronomical Journal | Year: 2012

Ultra-high-energy cosmic-ray heavy nuclei have recently been considered as originating from nearby low-luminosity gamma-ray bursts that are associated with Type Ibc supernovae. Unlike the power-law decay in long duration gamma-ray bursts, the light curve of these bursts exhibits complex UV/optical behavior: shock breakout dominated thermal radiation peaks at about 1 day, and, after that, nearly constant emission sustained by radioactive materials for tens of days. We show that the highly boosted heavy nuclei at PeV energy interacting with the UV/optical photon field will produce considerable TeV photons via the photodisintegration/photo-de-excitation process. It was later predicted that a thermal-like γ-ray spectrum peaks at about a few TeV, which may serve as evidence of nucleus acceleration. The future observations by the space telescope Fermi and by the ground atmospheric Cherenkov telescopes such as H.E.S.S., VERITAS, and MAGIC will shed light on this prediction. © 2012. The American Astronomical Society. All rights reserved.

Liu X.-W.,Chinese Academy of Sciences | Liu X.-W.,University of Chinese Academy of Sciences | Liu X.-W.,Joint Center for Particle Nuclear Physics and Cosmology | Wu X.-F.,Chinese Academy of Sciences | And 4 more authors.
New Astronomy | Year: 2010

We calculate the diffuse high energy (TeV-PeV) neutrino emission from hyperflares of soft-gamma repeaters (SGRs), like the hyperflare risen from SGR 1806-20 on December 27 of 2004, within the framework of the fireball model. The fireball model for gamma-ray bursts (GRBs) can explain well the main features of this hyperflare and the subsequent multi-frequency afterglow emission. The expected rate, ∼ 20 s(-) 100 Gpc- 3 day- 1, of such hyperflares is well in excess of the GRBs rate. Our result shows that the contribution to the diffuse TeV-PeV neutrino background from such hyperflares is less than 10% of the contribution from GRBs. We also discuss the high energy cosmic rays (CRs) from these sources. © 2009 Elsevier B.V. All rights reserved.

Ackermann M.,Kavli Institute for Particle Astrophysics and Cosmology | Asano K.,Tokyo Institute of Technology | Atwood W.B.,University of California at Santa Cruz | Axelsson M.,University of Stockholm | And 224 more authors.
Astrophysical Journal | Year: 2010

We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi observatory. GRB 090510 is the first burst detected by the LAT that shows strong evidence for a deviation from a Band spectral fitting function during the prompt emission phase. The time-integrated spectrum is fit by the sum of a Band function with E peak = 3.9 ± 0.3MeV, which is the highest yet measured, and a hard power-law component with photon index -1.62 ± 0.03 that dominates the emission below ≈ 20keV and above ≈ 100MeV. The onset of the high-energy spectral component appears to be delayed by ≈ 0.1s with respect to the onset of a component well fit with a single Band function. A faint GBM pulse and a LAT photon are detected 0.5s before the main pulse. During the prompt phase, the LAT detected a photon with energy 30.5+5.8 -2.6GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, Γ≳1200, using simple γγ opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the ≈ 100keV-few MeV flux. Stricter high confidence estimates imply Γ ≳ 1000 and still require that the outflows powering short GRBs are at least as highly relativistic as those of long-duration GRBs. Implications of the temporal behavior and power-law shape of the additional component on synchrotron/synchrotron self-Compton, external-shock synchrotron, and hadronic models are considered. © 2010. The American Astronomical Society. All rights reserved.

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