Efficient identification of exoplanetary transit candidates from SuperWASP light curves

Transiting extrasolar planets constitute only a small fraction of the range of stellar systems found to display periodic, shallow dimmings in wide-field surveys employing small-aperture camera arrays. Here we present an efficient selection strategy for follow-up observations, derived from analysis of the light curves of a sample of 67 SuperWASP targets that passed the selection tests we used in earlier papers, but which have subsequently been identified either as planet hosts or as astrophysical false positives. We determine the system parameters using Markov-chain Monte Carlo analysis of the SuperWASP light curves. We use a constrained optimization of ?2 combined with a Bayesian prior based on the main-sequence mass and radius expected from the Two Micron All Sky Survey J ? H colour. The Bayesian nature of the analysis allows us to quantify both the departure of the host star from the main-sequence mass�radius relation and the probability that the companion radius is less than 1.5 Jupiter radii. When augmented by direct light-curve analyses that detect binaries with unequal primary and secondary eclipses, and objects with aperture blends that are resolved by SuperWASP, we find that only 13 of the original 67 stars, including the three known planets in the sample, would qualify for follow-up. This suggests that planet discovery �hit rates� better than one-in-five should be achievable. In addition, the stellar binaries that qualify are likely to have astrophysically interesting stellar or substellar secondaries.Monthly Notices of the Royal Astronomical Society 380(3), 1230-1244. (2007)0035-871

WASP-1b and WASP-2b: two new transiting exoplanets detected with SuperWASP and SOPHIE

We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219-0005465 (GSC 02265-00107 = WASP-1) and USNO-B1.0 0964-0543604 (GSC 00522-01199 = WASP-2). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radialvelocity variations and fits to the transit light curves yield estimates of the planetary masses and radii.WASP-1b andWASP-2b have orbital periods of 2.52 and 2.15 d, respectively. Given mass estimates for their F7V and K1V primaries, we derive planet masses 0.80-0.98 and 0.81-0.95 times that of Jupiter, respectively. WASP-1b appears to have an inflated radius of at least 1.33 RJup, whereas WASP-2b has a radius in the range 0.65-1.26 RJup.Monthly Notices of the Royal Astronomical Society 375(3), 951-957. (2007)0035-871

WASP-3b: a strongly irradiated transiting gas-giant planet

We report the discovery of WASP-3b, the third transiting exoplanet to be discovered by the WASP and SOPHIE collaboration.WASP-3b transits its host star USNO-B1.0 1256?0285133 every 1.846 834 � 0.000 002 d. Our high-precision radial velocity measurements present a variation with amplitude characteristic of a planetary-mass companion and in phase with the light curve. Adaptive optics imaging shows no evidence for nearby stellar companions, and line-bisector analysis excludes faint, unresolved binarity and stellar activity as the cause of the radial velocity variations. We make a preliminary spectroscopic analysis of the host star and find it to have Teff = 6400 � 100K and log g = 4.25 � 0.05 which suggests it is most likely an unevolved main-sequence star of spectral type F7-8V. Our simultaneous modelling of the transit photometry and reflex motion of the host leads us to derive a mass of 1.76+0.08 ?0.14 MJ and radius 1.31+0.07 ?0.14 RJ for WASP-3b. The proximity and relative temperature of the host star suggests that WASP-3b is one of the hottest exoplanets known, and thus has the potential to place stringent constraints on exoplanet atmospheric models.Monthly Notices of the Royal Astronomical Society 385(3), 1576-1584. (2008)0035-871

Innovation Cycles and Urban Dynamics

International audienceUrban systems are adaptive systems, in the sense that they continuously renew their structure while fulfilling very different functionalities. Many examples of adaptation in city size, spacing, and their social and functional components have been given in Chapter 6 of this book. There, we defined the structure of urban systems as a rather persistent configuration of relative and relational properties differentiating cities, which, over long periods, maintains the same cities in categories of size or socio-economic specialization. The content of these categories changes in terms ofthe quantitative thresholds or the qualitative attributes used for defining them at each date, but they retain the same meaning in terms of the relative situation of cities in the urban systems. Hierarchical differentiation and socio-economic specialization are the major structural features shared by all city systems. On the scale of national, continental, or world urban systems, the structures result mainly from self-organization processes, even if intentional decisions made by individuals or institutions (for instance, the choice of Brussels for the seat of many European Union institutions) may sometimes influence the general configuration