87,364 research outputs found
Can cold quark matter be solid?
The state of cold quark matter really challenges both astrophysicists and
particle physicists, even many-body physicists. It is conventionally suggested
that BCS-like color superconductivity occurs in cold quark matter; however,
other scenarios with a ground state rather than of Fermi gas could still be
possible. It is addressed that quarks are dressed and clustering in cold quark
matter at realistic baryon densities of compact stars, since a weakly coupling
treatment of the interaction between constituent quarks would not be reliable.
Cold quark matter is conjectured to be in a solid state if thermal kinematic
energy is much lower than the interaction energy of quark clusters, and such a
state could be relevant to different manifestations of pulsar-like compact
stars.Comment: Proceedings of IWARA2009 (IJMP D
Solid Quark Stars?
It is conjectured that cold quark matter with much high baryon density could
be in a solid state, and strange stars with low temperatures should thus be
solid stars. The speculation could be close to the truth if no peculiar
polarization of thermal X-ray emission (in, e.g., RXJ1856), or no gravitational
wave in post-glitch phases, is detected in future advanced facilities, or if
spin frequencies beyond the critical ones limited by r-mode instability are
discovered. The shear modulus of solid quark matter could be ~ 10^{32} erg/cm^3
if the kHz QPOs observed are relevant to the eigenvalues of the center star
oscillations.Comment: Revised significantly, ApJL accepted, or at
http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.ht
Can the age discrepancies of neutron stars be circumvented by an accretion-assisted torque?
It is found that 1E 1207.4-5209 could be a low-mass bare strange star if its
small radius or low altitude cyclotron formation can be identified. The age
problems of five sources could be solved by a fossil-disk-assisted torque. The
magnetic dipole radiation dominates the evolution of PSR B1757-24 at present,
and the others are in propeller (or tracking) phases.Comment: ApJL accepted, or at
http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.ht
Wind braking of magnetars: to understand magnetar's multiwave radiation properties
Magnetars are proposed to be peculiar neutron stars powered by their super
strong magnetic field. Observationally, anomalous X-ray pulsars and soft
gamma-ray repeaters are believed to be magnetar candidates. While more and more
multiwave observations of magnetars are available, unfortunately, we see
accumulating failed predictions of the traditional magnetar model. These
challenges urge rethinking of magnetar. Wind braking of magnetars is one of the
alternative modelings. The release of magnetic energy may generate a particle
outflow (i.e., particle wind), that results in both an anomalous X-ray
luminosity and significantly high spindown rate. In this wind braking scenario,
only strong multipole field is necessary for a magnetar (a strong dipole field
is no longer needed). Wind braking of magnetars may help us to understand their
multiwave radiation properties, including (1) Non-detection of magnetars in
Fermi-LAT observations, (2) The timing behaviors of low magnetic field
magnetars, (3) The nature of anti-glitches, (4) The criterion for magnetar's
radio emission, etc. In the wind braking model of magentars, timing events of
magnetars should always be accompanied by radiative events. It is worth noting
that the wind engine should be the central point in the research since other
efforts with any reasonable energy mechanism may also reproduce the results.Comment: 6 pages, 1 figure, submitted to conference proceeding of SMFNS2013
(Strong electromagnetic field and neutron stars 2013
- …