24,326 research outputs found
Quantum Key Distribution by Utilizing Four-Level Particles
We present a quantum key distribution protocol based on four-level particles
entanglement. Furthermore, a controlled quantum key distribution protocol is
proposed by utilizing three four-level particles. We show that the two
protocols are secure.Comment: 5 pages, no figur
Asteroseismic Study on Cluster Distance Moduli for RGB Stars in NGC 6791 and NGC 6819
Stellar distance is an important basic parameter in stellar astrophysics.
Stars in a cluster are thought to be formed coevally from the same interstellar
cloud of gas and dust. They are therefore expected to have common properties.
These common properties strengthen our ability to constrain theoretical models
and/or to determine fundamental parameters, such as stellar mass, metal
fraction, and distance when tested against an ensemble of cluster stars. Here
we derive a new relation based on solar-like oscillations, photometric
observations, and the theory of stellar structure and evolution of red giant
branch stars to determine cluster distance moduli through the global
oscillation parameters and , and photometric data
\textit{V}. The values of and are derived from
\textit{kepler} observations. At the same time, it is used to interpret the
trends between \textit{V} and . From the analyses of this newly
derived relation and observational data of NGC 6791 and NGC 6819 we devise a
method in which all stars in a cluster are regarded as one entity to determine
the cluster distance modulus. This approach fully reflects the characteristic
of member stars in a cluster as a natural sample. From this method we derive
true distance moduli of mag for NGC 6791 and mag
for NGC 6819. Additionally, we find that the distance modulus only slightly
depends on the metallicity [Fe/H] in the new relation. A change of 0.1 dex in
[Fe/H] will lead to a change of 0.06 mag in the distance modulus.Comment: 9 pages, 6 figures, 4 tables, accepted Ap
New asteroseismic scaling relations based on Hayashi track relation applied to red-giant branch stars in NGC 6791 and NGC 6819
Stellar mass , radius , and gravity are important basic parameters
in stellar physics. Accurate values for these parameters can be obtained from
the gravitational interaction between stars in multiple systems or from
asteroseismology. Stars in a cluster are thought to be formed coevally from the
same interstellar cloud of gas and dust. The cluster members are therefore
expected to have some properties in common. These common properties strengthen
our ability to constrain stellar models and asteroseismically derived ,
and when tested against an ensemble of cluster stars. Here we derive new
scaling relations based on a relation for stars on the Hayashi track
() to determine the masses and metallicities of
red giant branch stars in open clusters NGC 6791 and NGC 6819 from the global
oscillation parameters (the large frequency separation) and
(frequency of maximum oscillation power). The and
values are derived from \kepler\ observations. From the
analysis of these new relations we derive: (1) direct observational evidence
that the masses of red giant branch stars in a cluster are the same within
their uncertainties, (2) new methods to derive and of the cluster in a
self consistent way from and , with lower intrinsic
uncertainties, (3) the mass dependence in the -
relation for red giant branch stars.Comment: open clusters and associations: individual (NGC 6791, NGC 6819) --
stars: late-type -- stars: fundamental parameters -- stars: interiors --
stars: oscillations -- asteroseismolog
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