4,824 research outputs found
The Allowed Parameter Space of a Long-lived Neutron Star as the Merger Remnant of GW170817
Due to the limited sensitivity of the current gravitational wave (GW) detectors, the central remnant of the binary neutron star (NS) merger associated with GW170817 remains an open question. In view of the relatively large total mass, it is generally proposed that the merger of GW170817 would lead to a short-lived hypermassive NS or directly produce a black hole (BH). There is no clear evidence to support or rule out a long-lived NS as the merger remnant. Here, we utilize the GW and electromagnetic (EM) signals to comprehensively investigate the parameter space that allows a long-lived NS to survive as the merger remnant of GW170817. We find that for some stiff equations of state, the merger of GW170817 could, in principle, lead to a massive NS, which has a millisecond spin period. The post-merger GW signal could hardly constrain the ellipticity of the NS. If the ellipticity reaches 10−3, in order to be compatible with the multi-band EM observations, the dipole magnetic field of the NS (B p ) is constrained to the magnetar level of ~1014 G. If the ellipticity is smaller than 10−4, B p is constrained to the level of ~109–1011 G. These conclusions weakly depend on the adoption of the NS equation of state
The GRB-Supernova Connection
Long-duration gamma-ray bursts (GRBs) are believed to be produced by the core
collapse of massive stars and hence to be connected with supernovae (SNe).
Indeed, for four pairs of GRBs and SNe, spectroscopically confirmed connection
has been firmly established. For more than a dozen of GRBs the SN signature
(the `red bump') has been detected in the afterglow lightcurves. Based on the
four pairs of GRBs and SNe with spectroscopically confirmed connection a tight
correlation was found between the peak spectral energy of GRBs and the peak
bolometric luminosity of the underlying SNe. The recent discovery of X-ray
flash 080109 associated with a normal core-collapse SN 2008D confirmed this
relation and extended the GRB-SN connection. Progress on the GRB-SN connection
is briefly reviewed.Comment: 6 pages, 5 figures. To appear in the proceedings of "2008 Nanjing GRB
conference", Nanjing, 23-27 June 200
First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl
Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are
calculated using the first-principles molecular dynamics method. Evolution of
electronic structures as well as the influence of the approximate description
of ionization on pressure (caused by the underestimation of the energy gap
between conduction bands and valence bands) in the first-principles method are
illustrated by the calculation. Pressure ionization and thermal smearing are
shown as the major factors to prevent the deviation of pressure from global
accumulation along the Hugoniot. In addition, cancellation between electronic
kinetic pressure and virial pressure further reduces the deviation. The
calculation of X-ray absorption spectra shows that the band gap of KCl persists
after the pressure ionization of the electrons of Cl and K taking place at
lower energy, which provides a detailed understanding to the evolution of
electronic structures of warm dense matter
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