6,448 research outputs found
Dynamical spacetimes and gravitational radiation in a Fully Constrained Formulation
This contribution summarizes the recent work carried out to analyze the
behavior of the hyperbolic sector of the Fully Constrained Formulation (FCF)
derived in Bonazzola et al. 2004. The numerical experiments presented here
allows one to be confident in the performances of the upgraded version of
CoCoNuT's code by replacing the Conformally Flat Condition (CFC) approximation
of the Einstein equations by the FCF.Comment: 4 pages, 7 figures. Accepted for publication in Journal of Physics:
Conference Series, Proceedings of the 8th Edoardo Amaldi Conference on
Gravitational Wave
The Effect of Zonally Asymmetric Ozone Heating on the Northern Hemisphere Winter Polar Stratosphere
[1] Previous modeling studies have found significant differences in winter extratropical stratospheric temperatures depending on the presence or absence of zonally asymmetric ozone heating (ZAOH), yet the physical mechanism causing these differences has not been fully explained. The present study describes the effect of ZAOH on the dynamics of the Northern Hemisphere extratropical stratosphere using an ensemble of free-running atmospheric general circulation model simulations over the 1 December - 31 March period. We find that the simulations including ZAOH produce a significantly warmer and weaker stratospheric polar vortex in mid-February due to more frequent major stratospheric sudden warmings compared to the simulations using only zonal mean ozone heating. This is due to regions of enhanced Eliassen-Palm flux convergence found in the region between 40°N–70°N latitude and 10–0.05 hPa. These results are consistent with changes in the propagation of planetary waves in the presence of ZAOH predicted by an ozone-modified refractive index
A comparative study of two 47 Tuc giant stars with different s-process enrichment
Here we aim to understand the origin of 47 Tuc's La-rich star Lee 4710. We
report abundances for O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Zn, Y, Zr,
Ba, La, Ce, Pr, Nd, and Eu, and present a detailed abundance analysis of two 47
Tuc stars with similar stellar parameters but different slow neutron-capture
(s-)process enrichment. Star Lee 4710 has the highest known La abundance ratio
in this cluster ([La/Fe] = 1.14), and star Lee 4626 is known to have normal
s-process abundances (e.g., [Ba/Eu]). The nucleosynthetic pattern of
elements with Z56 for star Lee 4710 agrees with the predicted yields
of a asymptotic giant branch (AGB) star. Therefore, Lee 4710 may
have been enriched by mass transfer from a more massive AGB companion, which is
compatible with its location far away from the center of this relatively
metal-rich ([Fe/H]) globular cluster. A further analysis comparing
the abundance pattern of Lee 4710 with data available in the literature reveals
that nine out of the 47 Tuc stars previously studied show strong
s-process enhancements that point towards later enrichment by more massive AGB
stars.Comment: ApJL in press. 6 pages, 4 figure
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