40,176 research outputs found
Abundances in the Uranium-Rich Star CS 31082-001
The recent discovery by Cayrel et al. of U in CS 31082-001 along with Os and
Ir at greatly enhanced abundances but with [Fe/H]=-2.9 strongly reinforces the
argument that there are at least two kinds of SNII sources for r-nuclei. One
source is the high-frequency H events responsible for heavy r-nuclei (A>135)
but not Fe. The H-yields calculated from data on other ultra-metal-poor stars
and the sun provide a template for quantitatively predicting the abundances of
all other r-elements. In CS 31082-001 these should show a significant
deficiency at A<135 relative to the solar r-pattern. It is proposed that CS
31082-001 should have had a companion that exploded as an SNII H event. If the
binary survived the explosion, this star should now have a compact companion,
most likely a stellar-mass black hole. Comparison of abundance data with
predicted values and a search for a compact companion should provide a
stringent test of the proposed r-process model. The U-Th age determined by
Cayrel et al. for CS 31082-001 is, to within substantial uncertainties, in
accord with the r-process age determined from solar system data. The time gap
between Big Bang and onset of normal star formation only allows r-process
chronometers to provide a lower limit on the age of the universe.Comment: 5 pages, 1 figur
SS Ari: a shallow-contact close binary system
Two CCD epochs of light minimum and a complete R light curve of SS Ari are
presented. The light curve obtained in 2007 was analyzed with the 2003 version
of the W-D code. It is shown that SS Ari is a shallow contact binary system
with a mass ratio and a degree of contact factor f=9.4(\pm0.8%). A
period investigation based on all available data shows that there may exist two
distinct solutions about the assumed third body. One, assuming eccentric orbit
of the third body and constant orbital period of the eclipsing pair results in
a massive third body with and P_3=87.00.278M_{\odot}$. Both of the cases
suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table
High Fill-Out, Extreme Mass Ratio Overcontact Binary Systems. X. The new discovered binary XY Leonis Minoris
The new discovered short-period close binary star, XY LMi, was monitored
photometrically since 2006. It is shown that the light curves are typical
EW-type and show complete eclipses with an eclipse duration of about 80
minutes. By analyzing the complete B, V, R, and I light curves with the 2003
version of the W-D code, photometric solutions were determined. It is
discovered that XY LMi is a high fill-out, extreme mass ratio overcontact
binary system with a mass ratio of q=0.148 and a fill-out factor of f=74.1%,
suggesting that it is on the late evolutionary stage of late-type tidal-locked
binary stars. As observed in other overcontact binary stars, evidence for the
presence of two dark spots on both components are given. Based on our 19
epoches of eclipse times, it is found that the orbital period of the
overcontact binary is decreasing continuously at a rate of
dP/dt=-1.67\times10^{-7}\,days/year, which may be caused by the mass transfer
from the primary to the secondary or/and angular momentum loss via magnetic
stellar wind. The decrease of the orbital period may result in the increase of
the fill-out, and finally, it will evolve into a single rapid-rotation star
when the fluid surface reaching the outer critical Roche Lobe.Comment: 19 pages, 4 figures, 9 table
Kinematics and flux evolution of superluminal components in QSO B1308+326
Search for Doppler-boosting effect in flux evolution of superluminal
components in blazars has been an important subject, which can help clarify
their kinematic and emission properties. The kinematics and flux evolution
observed at 15GHz for the three superluminal components (knot-c, -i and -k) in
QSO B1308+326 (z=0.997) were investigated in detail. It is shown that the
precessing jet nozzle model previously proposed by Qian et al. (1991, 2014,
2017, 2022a, 2022b) can be used to fully simulate their kinematics on pc-scales
with a nozzle precession period of 16.9 yr. With the acceleration/deceleration
in their motion found in the model-simulation of their kinematics we can derive
their bulk Lorentz factor and Doppler factor as function of time and predict
their Doppler-boosting effect. Interestingly, the flux evolution of the three
superluminal components can be well interpreted in terms of their
Doppler-boosting effect. The full explanation of both their kinematic behavior
and flux evolution validates our precessing nozzle model and confirms that
superluminal components are physical entities moving relativistically toward us
at small viewing angles.Comment: 13 pages, 41 figure
Flux evolution and kinematics of superluminal components in blazar 3C345
The precessing jet-nozzle scenario previously proposed was applied to
model-fit the kinematics of five superluminal components (C19,C20,C21,B5 and
B7) of jet-B in blazar 3C345. Based on a specific pattern for the the
precessing common trajectory of jet-B, the kinematic properties (including
trajectory,coordinates, core separation and apparent velocity) were
model-fitted and their flux evolution could be studied. Through
model-simulation of their kinematic behavior, the bulk Lorentz factor, viewing
angle and Doppler factor were derived as continuous functions of time and the
association of their flux evolution with their Doppler-boosting effect was
investigated. The 43GHz light-curves of the five superluminal components can be
well interpreted in terms of their Doppler effect. The close association of
their flux evolution with the Doppler-boosting effect firmly validates our
precessing nozzle scenario and supports the traditional point-view that
superluminal components are physical entities (traveling shocks or plasmoids)
participating relativistic motion toward us at small angles. The
model-simulation of kinematic behavior of superluminal components by using our
precessing nozzle scenario with specific patterns (helical or ballistic)
assumed for the precessing common trajectories yields the model-derived bulk
Lorentz factor, apparent velocity, viewing angle and Doppler factor as
continuous functions of time, which are most applicable to study the connection
of flux evolution with Doppler boosting effect for the superluminal components.Comment: 18 pages and 63 figure
Relative Entropy: Free Energy Associated with Equilibrium Fluctuations and Nonequilibrium Deviations
Using a one-dimensional macromolecule in aqueous solution as an illustration,
we demonstrate that the relative entropy from information theory, , has a natural role in the energetics of equilibrium and
nonequilibrium conformational fluctuations of the single molecule. It is
identified as the free energy difference associated with a fluctuating density
in equilibrium, and is associated with the distribution deviate from the
equilibrium in nonequilibrium relaxation. This result can be generalized to any
other isothermal macromolecular systems using the mathematical theories of
large deviations and Markov processes, and at the same time provides the
well-known mathematical results with an interesting physical interpretations.Comment: 5 page
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