118 research outputs found
The effect of stellar limb darkening values on the accuracy of the planet radii derived from photometric transit observations
We study how the precision of the exoplanet radius determination is affected
by our present knowledge of limb darkening in two cases: when we fix the limb
darkening coefficients and when we adjust them. We also investigate the effects
of spots in one-colour photometry. We study the effect of limb darkening on the
planetary radius determination both via analytical expressions and by numerical
experiments. We also compare some of the existing limb darkening tables. When
stellar spots affect the fit, we replace the limb darkening coefficients,
calculated for the unspotted cases, with effective limb darkening coefficients
to describe the effect of the spots. There are two important cases. (1) When
one fixes the limb darkening values according to some theoretical predictions,
the inconsistencies of the tables do not allow us to reach accuracy in the
planetary radius of better than 1-10% (depending on the impact parameter) if
the host star's surface effective temperature is higher than 5000 K. Below 5000
K the radius ratio determination may contain even 20% error. (2) When one
allows adjustment of the limb darkening coefficients, the a/Rs ratio, the
planet-to-stellar radius ratio, and the impact parameter can be determined with
sufficient accuracy (<1%), if the signal-to-noise ratio is high enough.
However, the presence of stellar spots and faculae can destroy the agreement
between the limb darkening tables and the fitted limb darkening coefficients,
but this does not affect the precision of the planet radius determination. We
also find that it is necessary to fit the contamination factor, too. We
conclude that the present inconsistencies of theoretical stellar limb darkening
tables suggests one should not fix the limb darkening coefficients. When one
allows them to be adjusted, then the planet radius, impact parameter, and the
a/Rs can be obtained with the required precision.Comment: Astronomy & Astrophysics Vol. 549, A9 (2013) - 11 page
Transiting exoplanets from the CoRoT space mission. XXVII. CoRoT-28b, a planet orbiting an evolved star, and CoRoT-29b, a planet showing an asymmetric transit
Transiting exoplanets from the CoRoT space mission XXI. CoRoT-19b: A low density planet orbiting an old inactive F9V-star
Observations of transiting extrasolar planets are of key importance to our
understanding of planets because their mass, radius, and mass density can be
determined. The CoRoT space mission allows us to achieve a very high
photometric accuracy. By combining CoRoT data with high-precision radial
velocity measurements, we derive precise planetary radii and masses. We report
the discovery of CoRoT-19b, a gas-giant planet transiting an old, inactive
F9V-type star with a period of four days. After excluding alternative physical
configurations mimicking a planetary transit signal, we determine the radius
and mass of the planet by combining CoRoT photometry with high-resolution
spectroscopy obtained with the echelle spectrographs SOPHIE, HARPS, FIES, and
SANDIFORD. To improve the precision of its ephemeris and the epoch, we observed
additional transits with the TRAPPIST and Euler telescopes. Using HARPS spectra
obtained during the transit, we then determine the projected angle between the
spin of the star and the orbit of the planet. We find that the host star of
CoRoT-19b is an inactive F9V-type star close to the end of its main-sequence
life. The host star has a mass M*=1.21+/-0.05 Msun and radius R*=1.65+/-0.04
Rsun. The planet has a mass of Mp=1.11+/-0.06 Mjup and radius of Rp=1.29+/-0.03
Rjup. The resulting bulk density is only rho=0.71+/-0.06 gcm-3, which is much
lower than that for Jupiter. The exoplanet CoRoT-19b is an example of a giant
planet of almost the same mass as Jupiter but a 30% larger radius.Comment: 6 pages, 7 figure
Transiting exoplanets from the CoRoT space mission XVII. The hot Jupiter CoRoT-17b: a very old planet
We report on the discovery of a hot Jupiter-type exoplanet, CoRoT-17b,
detected by the CoRoT satellite. It has a mass of \Mjup and a
radius of \Rjup, while its mean density is g/cm.
CoRoT-17b is in a circular orbit with a period of days. The
host star is an old ( Gyr) main-sequence star, which makes it an
intriguing object for planetary evolution studies. The planet's internal
composition is not well constrained and can range from pure H/He to one that
can contain 380 earth masses of heavier elements.Comment: Published (A&A 531, A41, 2011
Disease-Toxicant Interactions in Manganese Exposed Huntington Disease Mice: Early Changes in Striatal Neuron Morphology and Dopamine Metabolism
YAC128 Huntington's disease (HD) transgenic mice accumulate less manganese (Mn) in the striatum relative to wild-type (WT) littermates. We hypothesized that Mn and mutant Huntingtin (HTT) would exhibit gene-environment interactions at the level of neurochemistry and neuronal morphology. Twelve-week-old WT and YAC128 mice were exposed to MnCl2-4H2O (50 mg/kg) on days 0, 3 and 6. Striatal medium spiny neuron (MSN) morphology, as well as levels of dopamine (DA) and its metabolites (which are known to be sensitive to Mn-exposure), were analyzed at 13 weeks (7 days from initial exposure) and 16 weeks (28 days from initial exposure). No genotype-dependent differences in MSN morphology were apparent at 13 weeks. But at 16 weeks, a genotype effect was observed in YAC128 mice, manifested by an absence of the wild-type age-dependent increase in dendritic length and branching complexity. In addition, genotype-exposure interaction effects were observed for dendritic complexity measures as a function of distance from the soma, where only YAC128 mice were sensitive to Mn exposure. Furthermore, striatal DA levels were unaltered at 13 weeks by genotype or Mn exposure, but at 16 weeks, both Mn exposure and the HD genotype were associated with quantitatively similar reductions in DA and its metabolites. Interestingly, Mn exposure of YAC128 mice did not further decrease DA or its metabolites versus YAC128 vehicle exposed or Mn exposed WT mice. Taken together, these results demonstrate Mn-HD disease-toxicant interactions at the onset of striatal dendritic neuropathology in YAC128 mice. Our results identify the earliest pathological change in striatum of YAC128 mice as being between 13 to 16 weeks. Finally, we show that mutant HTT suppresses some Mn-dependent changes, such as decreased DA levels, while it exacerbates others, such as dendritic pathology
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A systematic review of parental involvement in cognitive behavioural therapy for adolescent anxiety disorders
Anxiety disorders are common among adolescents and lead to poor long-term outcomes. Cognitive Behavioural Therapy (CBT) is an evidenced-based intervention for adolescent anxiety disorders, but little is known about whether and how parents should be involved. This systematic review evaluated how parents have been involved and associated treatment outcomes in studies of CBT for adolescent anxiety disorders. Electronic systematic searches were conducted in PsycINFO, Embase, CINAHL, Medline, AMED databases, to identify studies investigating CBT for adolescent anxiety disorder(s) that included parents in treatment. Twenty-three studies were identified. Parents were involved in treatment in a number of different ways: by attending separate parent sessions, joint parent-adolescent sessions, or both, or through provision of a workbook while attending some adolescent sessions. Content varied but was most typically aimed at the parent developing an understanding of core CBT components and skills to help them manage their adolescent’s anxiety and avoidance. Treatment outcomes indicate that CBT with parental involvement is an effective intervention for adolescent anxiety disorders, however it is not possible to draw conclusions regarding whether parental involvement (generally or in any particular form) enhances treatment outcomes. Poor reporting and methodological issues also limit the conclusions. Further research is required to identify whether there are particular types of parental involvement in CBT that bring clinical benefits to adolescents with anxiety disorders generally, as well as in particular circumstances
Knowing What is Good for You. Empirical Analysis of Personal Preferences and the 'Objective Good'
Derivation of the parameters of CoRoT planets
We explore the influence that limb darkening and stellar activity have in the determination of planetary parameters, highlighting the impact that they have in space-based surveys, such as CoRoT
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