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 corrections; version sent to the printer w few upgrade

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

Conduction sous champ électrique faible dans les liquides isolants. Influence de la distance inter-électrodes

This study relates the phenomena of electric conduction in a dielectric liquid under a weak electric field. In the first part the equations of the diffuse layer perturbed by a weak electric field are established. The solutions are then computed numerically. It appears that one of the most important parameter is the space charge density appearing on the electrodes. This quantity is determined by streaming current experiments. In the second part, the experimental equipment is presented as well as the experiments. The liquid used is n heptane with several additives for different concentrations. The conductivity is measured in terms of the distance between the electrodes, the application time of the electric field and the additives concentration. We notice a sudden slope variation of the conductivity for a value of the concentration. The confrontation between experiments in terms of electrodes distance and the theoretical predictions is rather good.Dans cette étude, nous analysons les phénomènes de conduction électrique dans un liquide diélectrique soumis à un champ électrique faible entre deux électrodes planes parallèles. La première partie est une étude théorique dans laquelle nous présentons tout d'abord les équations générales de la couche diffuse correspondant au cas de la conduction sous champ électrique faible. La complexité des équations ne nous permet pas d'obtenir des solutions analytiques, mais nécessite un traitement numérique. Nous mettons alors en évidence qu'un des paramètres très importants est la densité volumique de charge apparaissant sur les électrodes. Ce paramètre conditionne le phénomène et il sera nécessaire de le déterminer par la mesure des courants d'écoulement. Dans la deuxième partie, nous présentons le dispositif expérimental utilisé ainsi que les résultats obtenus. Les expériences ont été faites avec de I'$n$ heptane contenant un certain nombre d'additifs à des concentrations variables. La conductivité est obtenue en fonction de la distance inter-électrodes, du temps d'application du champ électrique et de la concentration en additifs. L'analyse des résultats met en évidence une concentration pour laquelle une brusque variation de pente de la conductivité apparait. Par ailleurs, la confrontation entre les valeurs théoriques et expérimentales de la conductivité en fonction de la distance inter-électrodes montre une bonne concordance générale

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