40 research outputs found
Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius
We report the discovery of very shallow (DF/F = 3.4 10-4), periodic dips in
the light curve of an active V = 11.7 G9V star observed by the CoRoT satellite,
which we interpret as due to the presence of a transiting companion. We
describe the 3-colour CoRoT data and complementary ground-based observations
that support the planetary nature of the companion. Methods. We use CoRoT color
information, good angular resolution ground-based photometric observations in-
and out- of transit, adaptive optics imaging, near-infrared spectroscopy and
preliminary results from Radial Velocity measurements, to test the diluted
eclipsing binary scenarios. The parameters of the host star are derived from
optical spectra, which were then combined with the CoRoT light curve to derive
parameters of the companion. We examine carefully all conceivable cases of
false positives, and all tests performed support the planetary hypothesis.
Blends with separation larger than 0.40 arcsec or triple systems are almost
excluded with a 8 10-4 risk left. We conclude that, as far as we have been
exhaustive, we have discovered a planetary companion, named CoRoT-7b, for which
we derive a period of 0.853 59 +/- 3 10-5 day and a radius of Rp = 1.68 +/-
0.09 REarth. Analysis of preliminary radial velocity data yields an upper limit
of 21 MEarth for the companion mass, supporting the finding.
CoRoT-7b is very likely the first Super-Earth with a measured radius.Comment: Accepted in Astronomy and Astrophysics; typos and language
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Time, the Written Record, and Professional Practice: The Case of Contemporary Social Work
Drawing on a three year ethnographically-oriented study exploring contemporary professional social work writing, this paper focuses on a key concern: the amount of time taken up with writing, or ‘paperwork’. We explore the relationship between time and professional social work writing in three key ways. Firstly, as a discrete, measurable phenomenon - how much time is spent on writing? Secondly, as a textual dimension to social work writing – how do institutional documents drive particular entextualisations of time and how do social worker texts entextualise time? Thirdly, as a particular timespace configuration of lived experience - how is time experienced by professional social workers? Findings indicate that a dominant institutional chronotope is governing social work textual practice underpinned by an ideology of writing which is at odds with social workers’ desired practice and professional goals. Methodologically, the paper illustrates the value of combining a range of data and analytic tools, using textual and contextual data, as well as qualitative and quantitative frames of analysis
Transiting exoplanets from the CoRoT space mission. VIII. CoRoT-7b: the first super-Earth with measured radius
Copyright © The European Southern Observatory (ESO)Aims. We report the discovery of very shallow (ΔF/F ≈ 3.4×10−4), periodic dips in the light curve of an active V = 11.7 G9V star observed by the CoRoT satellite, which we interpret as caused by a transiting companion. We describe the 3-colour CoRoT data and complementary ground-based observations that support the planetary nature of the companion.
Methods. We used CoRoT colours information, good angular resolution ground-based photometric observations in- and out- of transit, adaptive optics imaging, near-infrared spectroscopy, and preliminary results from radial velocity measurements, to test the diluted eclipsing binary scenarios.
The parameters of the host star were derived from optical spectra, which were then combined with the CoRoT light curve to derive parameters of the companion.
Results. We examined all conceivable cases of false positives carefully, and all the tests support the planetary hypothesis. Blends with separation >0.40'' or triple systems are almost excluded with a 8 × 10−4 risk left. We conclude that, inasmuch we have been exhaustive, we have discovered a planetary companion, named CoRoT-7b, for which we derive a period of 0.853 59 ± 3 × 10−5 day and a radius of Rp = 1.68 ± 0.09 REarth. Analysis of preliminary radial velocity data yields an upper limit of 21 MEarth for the companion mass, supporting the finding.
Conclusions. CoRoT-7b is very likely the first Super-Earth with a measured radius. This object illustrates what will probably become a common situation with missions such as Kepler, namely the need to establish the planetary origin of transits in the absence of a firm radial velocity detection and mass measurement. The composition of CoRoT-7b remains loosely constrained without a precise mass. A very high surface temperature on its irradiated face, ≈1800–2600 K at the substellar point, and a very low one, ≈50 K, on its dark face assuming no atmosphere, have been derived
Reestruturação econômica, relações do trabalho e qualificação na indústria petroquímica no Rio Grande do Sul
Evolution de la charge électrique d'une particule heurtant une paroi solide
This study, essentially experimental, relates the electric charge generated by the shock of particles on a conducting wall (copper) and on an insulating one (polyethylene). The experiments are realised with an equipment connected to a data acquisition system. We have analysed the influence of differents parameters: impact angle; particle size; initial charge of the particles; impact velocity. Then from these experiments it is possible to point out the charging process of a particle for successive shocks.Le travail que nous présentons est une étude expérimentale du phénomène de génération de charges par collisions sur des surfaces métallique (cuivre) et isolante (polyéthylène). Les expériences sont réalisées sur un dispositif relié à un système d'acquisition de données. Nous avons procédé à l'étude de l'influence de plusieurs paramètres sur ce phénomène tels que : l'angle de choc ; les dimensions des particules ; la charge initiale des particules ; la vitesse au moment du choc. Nous avons aussi mis en évidence l'existence d'une charge de saturation qu'acquiert une particule après un grand nombre de chocs avec une paroi solide