27,237 research outputs found
HD 80606: Searching the chemical signature of planet formation
(Abridged) Binary systems with similar components are ideal laboratories
which allow several physical processes to be tested, such as the possible
chemical pattern imprinted by the planet formation process. Aims. We explore
the probable chemical signature of planet formation in the remarkable binary
system HD 80606 - HD 80607. The star HD 80606 hosts a giant planet with 4 MJup
detected by both transit and radial velocity techniques, being one of the most
eccentric planets detected to date. We study condensation temperature Tc trends
of volatile and refractory element abundances to determine whether there is a
depletion of refractories that could be related to the terrestrial planet
formation. Methods. We carried out a high-precision abundance determination in
both components of the binary system, using a line-by-line strictly
differential approach, using the Sun as a reference and then using HD 80606 as
reference. We used an updated version of the program FUNDPAR, together with
ATLAS9 model atmospheres and the MOOG code. Conclusions. From the study of Tc
trends, we concluded that the stars HD 80606 and HD 80607 do not seem to be
depleted in refractory elements, which is different for the case of the Sun.
Then, the terrestrial planet formation would have been less efficient in the
components of this binary system than in the Sun. The lack of a trend for
refractory elements with Tc between both stars implies that the presence of a
giant planet do not neccesarily imprint a chemical signature in their host
stars, similar to the recent result of Liu et al. (2014). This is also in
agreement with Melendez et al. (2009), who suggest that the presence of
close-in giant planets might prevent the formation of terrestrial planets.
Finally, we speculate about a possible planet around the star HD 80607.Comment: 19 pages, 9 figures, A&A accepte
Controlling the ellipticity of attosecond pulses produced by laser irradiation of overdense plasmas
The interaction of high-intensity laser pulses and solid targets provides a
promising way to create compact, tunable and bright XUV attosecond sources that
can become a unique tool for a variety of applications. However, it is
important to control the polarization state of this XUV radiation, and to do so
in the most efficient regime of generation. Using the relativistic electronic
spring (RES) model and particle-in-cell (PIC) simulations, we show that the
polarization state of the generated attosecond pulses can be tuned in a wide
range of parameters by adjusting the polarization and angle of incidence of the
laser radiation. In particular, we demonstrate the possibility of producing
circularly polarized attosecond pulses in a wide variety of setups.Comment: 6 pages, 3 figure
Computability of the causal boundary by using isocausality
Recently, a new viewpoint on the classical c-boundary in Mathematical
Relativity has been developed, the relations of this boundary with the
conformal one and other classical boundaries have been analyzed, and its
computation in some classes of spacetimes, as the standard stationary ones, has
been carried out.
In the present paper, we consider the notion of isocausality given by
Garc\'ia-Parrado and Senovilla, and introduce a framework to carry out
isocausal comparisons with standard stationary spacetimes. As a consequence,
the qualitative behavior of the c-boundary (at the three levels: point set,
chronology and topology) of a wide class of spacetimes, is obtained.Comment: 44 pages, 5 Figures, latex. Version with minor changes and the
inclusion of Figure
Isocausal spacetimes may have different causal boundaries
We construct an example which shows that two isocausal spacetimes, in the
sense introduced by Garc\'ia-Parrado and Senovilla, may have c-boundaries which
are not equal (more precisely, not equivalent, as no bijection between the
completions can preserve all the binary relations induced by causality). This
example also suggests that isocausality can be useful for the understanding and
computation of the c-boundary.Comment: Minor modifications, including the title, which matches now with the
published version. 12 pages, 3 figure
Precision radiative corrections to the Dalitz plot of baryon semileptonic decays including the spin-momentum correlation of the decaying baryon and the emitted charged lepton
We calculate the radiative corrections to the angular correlation between the
polarization of the decaying baryon and the direction of the emitted charged
lepton in the semileptonic decays of spin one-half baryons to order
(\alpha/\pi)(q/M_1). The final results are presented, first, with the triple
integration of the bremsstrahlung photon ready to be performed numerically and,
second, in an analytical form. A third presentation of our results in the form
of numerical arrays of coefficients to be multiplied on the quadratic products
of form factors is discussed. This latter may be the most practical one to use
in Monte Carlo simulations. A series of crosschecks is performed. The results
are useful in the analysis of the Dalitz plot of precision experiments
involving light and heavy quarks and is not compromised to fixing the form
factors at predetermined values. It is assumed that the real photons are
kinematically discriminated. Otherwise, our results have a general
model-independent applicability.Comment: 8 pages, RevTex4, 5 tables, no figures. Shortened version; results
and conclusions remain unchange
Precision radiative corrections to the semileptonic Dalitz plot with angular correlation between polarized decaying and emitted baryons: Effects of the four-body region
Analytical radiative corrections of order (\alpha/\pi)(q/M_1) are calculated
for the four-body region of the Dalitz plot of baryon semileptonic decays when
the s_1 \cdot p_2 correlation is present. Once the final result is available,
it is possible to exhibit it in terms of the corresponding final result of the
three-body region following a set of simple changes in the latter. We cover two
cases, a charged and a neutral polarized decaying baryon.Comment: Revtex4, 7 pages, no figure
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