51 research outputs found
On the potential of transit surveys in star clusters: Impact of correlated noise and radial velocity follow-up
We present an extension of the formalism recently proposed by Pepper & Gaudi
to evaluate the yield of transit surveys in homogeneous stellar systems,
incorporating the impact of correlated noise on transit time-scales on the
detectability of transits, and simultaneously incorporating the magnitude
limits imposed by the need for radial velocity follow-up of transit candidates.
New expressions are derived for the different contributions to the noise budget
on transit time-scales and the least-squares detection statistic for box-shaped
transits, and their behaviour as a function of stellar mass is re-examined.
Correlated noise that is constant with apparent stellar magnitude implies a
steep decrease in detection probability at the high mass end which, when
considered jointly with the radial velocity requirements, can severely limit
the potential of otherwise promising surveys in star clusters. However, we find
that small-aperture, wide field surveys may detect hot Neptunes whose radial
velocity signal can be measured with present-day instrumentation in very nearby
(<100 pc) clusters.Comment: 14 pages, 2 figures, accepted for publication in MNRA
The Cepheid period-luminosity zero-point from radial velocities and Hipparcos proper motions
A value for the zero-point (ρ) of the Cepheid period-luminosity relation, = 2.81 log P + ρ, is deduced by comparing the value of the Oort constant, A, derived from radial velocities with that derived from Hipparcos proper motions. We find in this way that ρ =−1.47 ± 0.13, in excellent agreement with the value derived from Hipparcos trigonometrical parallaxes, ρ = −1.43 ± 0.10, by Feast & Catchpole in a recent pape
The "missing link": a 4-day period transiting exoplanet around OGLE-TR-111
We report the discovery of a transiting hot Jupiter around OGLE-TR-111, from
our radial velocity follow-up of OGLE transiting candidates in Carina. The
planet has a mass of 0.53 +- 0.11 M_J and a radius of 1.0 +0.13-0.06 R_J. Three
transiting exoplanets have already been found among OGLE candidates, all with
periods near 1.5 days. The planet presented here, with P=4.0 days, is the first
exoplanet detected by transits with the characteristics of a "normal" hot
Jupiter, as found in abundance by radial velocity surveys The radius of
OGLE-TR-111b and the scarcity of hot Jupiters detected among OGLE transit
candidates tend to indicate that the case of HD209458b, with a radius of 1.4
R_J, is exceptional, with most hot Jupiters being smaller.Comment: 4 pages, 4 figures, to be published in A&A Letter
La corrupción en la construcción de la imagen de la política en los noticieros de televisión
This work analyses the political news of eight Spanish television channels in order to see what image is built of politics, and particularly how the news of corruption affects the image of politics in Spanish news broadcasts. Different cases of corruption such as Gürtel, Palma Arena and those associated with judge Baltasar Garzón in his final stage in office, occupy part of the study. A new methodology is therefore proposed that enables the quality of the political information emitted from inside and outside the political content of the news programmes to be observed. Particular attention is paid to the news broadcasts of Televisión Española and Cuatro as those which offer a more balanced view of politics, and channels such as La Sexta, which give priority to a narrative construction of politics in the news programmes around causes of corruption.Este trabajo analiza la actualidad política de ocho canales de televisión españoles con el fin de observar qué imagen se construye de la política en ellos, y en particular cómo las noticias de corrupción afectan a la imagen de la política en los noticiarios españoles. Los diferentes casos de corrupción como Gürtel, Palma Arena y los relacionados con el juez Baltasar Garzón en su última etapa en el cargo, ocupan buena parte del estudio. Se propone una nueva metodología que permite establecer la calidad de la información política de los noticiarios televisivos. Televisión Española y Cuatro son los canales que ofrecen una visión más equilibrada de la política. Y canales como La Sexta dan prioridad a la construcción narrativa de las noticias políticas que tratan la corrupción
Star-Planet Interactions
Much effort has been invested in recent years, both observationally and
theoretically, to understand the interacting processes taking place in
planetary systems consisting of a hot Jupiter orbiting its star within 10
stellar radii. Several independent studies have converged on the same scenario:
that a short-period planet can induce activity on the photosphere and upper
atmosphere of its host star. The growing body of evidence for such magnetic
star-planet interactions includes a diverse array of photometric, spectroscopic
and spectropolarimetric studies. The nature of which is modeled to be strongly
affected by both the stellar and planetary magnetic fields, possibly
influencing the magnetic activity of both bodies, as well as affecting
irradiation and non-thermal and dynamical processes. Tidal interactions are
responsible for the circularization of the planet orbit, for the
synchronization of the planet rotation with the orbital period, and may also
synchronize the outer convective envelope of the star with the planet. Studying
such star-planet interactions (SPI) aids our understanding of the formation,
migration and evolution of hot Jupiters.Comment: 8 pages, proceedings of Cool Stars 15, St. Andrews, July 2008, to be
published in the Conference Proceedings Series of the American Institute of
Physics - "Star-planet interactions" splinter session summar
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