The effect of red noise on planetary transit detection

Since the discovery of short-period exoplanets a decade ago, photometric surveys have been recognized as a feasible method to detect transiting hot Jupiters. Many transit surveys are now underway, with instruments ranging from 10-cm cameras to the Hubble Space Telescope. However, the results of these surveys have been much below the expected capacity, estimated in the dozens of detections per year. One of the reasons is the presence of systematics (‘red noise') in photometric time-series. In general, yield predictions assume uncorrelated noise (‘white noise'). In this paper, we show that the effect of red noise on the detection threshold and the expected yields cannot be neglected in typical ground-based surveys. We develop a simple method to determine the effect of red noise on photometric planetary transit detections. This method can be applied to determine detection thresholds for transit surveys. We show that the detection threshold in the presence of systematics can be much higher than that with the assumption of white noise, and obeys a different dependence on magnitude, orbital period and the parameters of the survey. Our method can also be used to estimate the significance level of a planetary transit candidate (to select promising candidates for spectroscopic follow-up). We apply our method to the OGLE planetary transit search, and show that it provides a reliable description of the actual detection threshold with real correlated noise. We point out in what way the presence of red noise could be at least partly responsible for the dearth of transiting planet detections from existing surveys, and examine some possible adaptations in survey planning and strategy. Finally, we estimate the photometric stability necessary to the detection of transiting ‘hot Neptunes

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

Patterns in species richness and endemismof European freshwater fish

Aim To analyse the patterns in species richness and endemism of the native European riverine fish fauna, in the light of the Messinian salinity crisis and the Last Glacial Maximum (LGM). Location European continent. Methods After gathering native fish faunistic lists of 406 hydrographical networks, we defined large biogeographical regions with homogenous fish fauna, based on a hierarchical cluster analysis. Then we analysed and compared the patterns in species richness and endemism among these regions, as well as species–area relationships. Results Among the 233 native species present in the data set, the Cyprinidae family was strongly dominant (> 50% of the total number of species). Seven biogeographical regions were defined: Western Peri-Mediterranea, Central Peri-Mediterranea, Eastern Peri-Mediterranea, Ponto-Caspian Europe, Northern Europe, Central Europe and Western Europe. The highest regional species richness was observed for Central Peri-Mediterranea and Ponto-Caspian Europe. The highest endemic richness was found in Central Peri-Mediterranea. Species–area relationships were characterized by high slope values for Peri-Mediterranean Europe and low values for Central and Western Europe. Main conclusions The results were in agreement with the ‘Lago Mare’ hypothesis explaining the specificity of Peri-Mediterranean fish fauna, as well as with the history of recolonization of Central and Western Europe from Ponto-Caspian Europe following the LGM. The results also agreed with the mechanisms of speciation and extinction influencing fish diversity in hydrographical networks. We advise the use of the seven biogeographical regions for further studies, and suggest considering Peri-Mediterranean Europe and Ponto-Caspian Europe as ‘biodiversity hotspots’ for European riverine fish

ELODIE metallicity-biased search for transiting Hot Jupiters II. A very hot Jupiter transiting the bright K star HD189733

Among the 160 known exoplanets, mainly detected in large radial-velocity surveys, only 8 have a characterization of their actual mass and radius thanks to the two complementary methods of detection: radial velocities and photometric transit. We started in March 2004 an exoplanet-search programme biased toward high-metallicity stars which are more frequently host extra-solar planets. This survey aims to detect close-in giant planets, which are most likely to transit their host star. For this programme, high-precision radial velocities are measured with the ELODIE fiber-fed spectrograph on the 1.93-m telescope, and high-precision photometry is obtained with the CCD Camera on the 1.20-m telescope, both at the Haute-Provence Observatory. We report here the discovery of a new transiting hot Jupiter orbiting the star HD189733. The planetary nature of this object is confirmed by the observation of both the spectroscopic and photometric transits. The exoplanet HD189733b, with an orbital period of 2.219 days, has one of the shortest orbital periods detected by radial velocities, and presents the largest photometric depth in the light curve (~ 3%) observed to date. We estimate for the planet a mass of 1.15 +- 0.04 Mjup and a radius of 1.26 +- 0.03 RJup. Considering that HD189733 has the same visual magnitude as the well known exoplanet host star HD209458, further ground-based and space-based follow-up observations are very promising and will permit a characterization of the atmosphere and exosphere of this giant exoplanet.Comment: 5 pages, submitted to Astronomy & Astrophysic

Variabilité à long terme des peuplements de poissons : résultats provenant de rivières françaises et ouest africaines

La variabilité à long terme de 18 peuplements de poissons a été étudiée dans des rivières françaises et ouest africaines. Les principaux résultats sont les suivants : 1) le coefficient de variation (CV) de la richesse spécifique, le CV de l'abondance totale et le CV moyen des espèces constitutives du peuplement augmentent avec la durée de l'étude; 2) selon la classification proposée par GROSSMAN et al. (1990) basée sur le CV moyen de l'abondance des espèces, tous les peuplements étudiés rentrent dans la catégorie des peuplements à fortes fluctuations interannuelles. Cependant certaines populations (les salmonidés en Bretagne par exemple) présentent une faible variabilité de leur densité; 3) dans le Rhône, les peuplements dont les populations manifestent une grande variabilité interannuelle sont ceux présentant le plus grand taux de renouvellement en espèces. Ce résultat est en accord avec l'hypothèse de HORWITZ (1978, "extermination hypothesis"). (Résumé d'auteur

Manual for the application of the new European Fish Index - EFI+. A fish-based method to assess the ecological status of European running waters in support of the Water Framework Directive.

This manual describes the new European Fish Index – EFI+ - and its application software. The EFI+ software and manual have been developed within the EFI+ project. The EFI+ project was funded by the European Commission (EC) under the 6th Framework Programme, “Energy, Environment and Sustainable Development”, Key Action 1: Sustainable Management and Quality of Water of the European Commission (Specific Targeted Research Project FP6-2005-SSP-5-A, Task 4: Ecological status assessment – filling the gaps). In the year 2000, the EC adopted a new legislation, the Water Framework Directive (WFD). This new legislation, now implemented in 27 EU member countries, aims for good ecological conditions in all surface waters. Fishes are, for the first time, part of a European-wide monitoring network designed to assess the ecological status of running waters. Between 2001 and 2004 the EC funded the FAME project developed, evaluated and implemented new standardised fish-based methods to assess the ecological status of running waters in Europe (FP5, Energy, Environment and Sustainable Management. Key Action 1: Sustainable Management and Quality of Water, EVK1-CT-2001-00094, http://fame.boku.ac.at).The main output of the FAME project was the European Fish Index (EFI), the first standardised fish-based assessment method applicable across a wide range of European rivers. The EFI employs a number of environmental descriptors to predict biological reference conditions and then quantifies the deviation of the fish community structure from these reference conditions on a statistical basis. The EFI was developed mainly based on data from Western and Northern Europe and was calibrated against estimates of human pressures and impacts. Although a wide range of river types was included in the development of the EFI, some river types, e.g. very large rivers, were underrepresented. The EFI has now been tested by European countries within their national monitoring programmes and has been evaluated for use for reporting under the WFD. During this evaluation process a number of limitations were observed in the performance of the index. Therefore, the overall objective of the EFI+ project was to overcome the existing limitations of the EFI by developing a new, more accurate and pan-European fish index. The scientific and technological objectives were to (1) evaluate the applicability of the existing EFI and make necessary improvements in Central-Eastern Europe and Mediterranean ecoregions; (2) extend the scope of the existing EFI to cover large rivers; (3) analyse relationships between hydromorphological pressures (including continuity disruption) and fish assemblages to increase the accuracy of the EFI; (4) adapt the existing software to the requirements of the EFI+ to allow calculation of the ecological status for running waters. This manual is divided in two parts. Part I introduces the concepts and methods on which the EFI+ is based. This section gives an overview of the development of the new European Fish Index and its achievements to fulfil the objectives of the Water Framework Directive in terms of using fishes as indicators for assessing the ecological status of running waters. Part II is the instruction manual to the web-based software. It details the fish assemblage and environmental data required and the process for obtaining scores and classification of the ecological status of a sampling site (or set of sampling sites) using the EFI+ online software

Implementation options for DNA-based identification into ecological status assessment under the European Water Framework Directive

Assessment of ecological status for the European Water Framework Directive (WFD) is based on “Biological Quality Elements” (BQEs), namely phytoplankton, benthic flora, benthic invertebrates and fish. Morphological identification of these organisms is a time-consuming and expensive procedure. Here, we assess the options for complementing and, perhaps, replacing morphological identification with procedures using eDNA, metabarcoding or similar approaches. We rate the applicability of DNA-based identification for the individual BQEs and water categories (rivers, lakes, transitional and coastal waters) against eleven criteria, summarised under the headlines representativeness (for example suitability of current sampling methods for DNA-based identification, errors from DNA-based species detection), sensitivity (for example capability to detect sensitive taxa, unassigned reads), precision of DNA-based identification (knowledge about uncertainty), comparability with conventional approaches (for example sensitivity of metrics to differences in DNA-based identification), cost effectiveness and environmental impact. Overall, suitability of DNA-based identification is particularly high for fish, as eDNA is a well-suited sampling approach which can replace expensive and potentially harmful methods such as gill-netting, trawling or electrofishing. Furthermore, there are attempts to replace absolute by relative abundance in metric calculations. For invertebrates and phytobenthos, the main challenges include the modification of indices and completing barcode libraries. For phytoplankton, the barcode libraries are even more problematic, due to the high taxonomic diversity in plankton samples. If current assessment concepts are kept, DNA-based identification is least appropriate for macrophytes (rivers, lakes) and angiosperms/macroalgae (transitional and coastal waters), which are surveyed rather than sampled. We discuss general implications of implementing DNA-based identification into standard ecological assessment, in particular considering any adaptations to the WFD that may be required to facilitate the transition to molecular data

The SARS algorithm: detrending CoRoT light curves with Sysrem using simultaneous external parameters

Surveys for exoplanetary transits are usually limited not by photon noise but rather by the amount of red noise in their data. In particular, although the CoRoT spacebased survey data are being carefully scrutinized, significant new sources of systematic noises are still being discovered. Recently, a magnitude-dependant systematic effect was discovered in the CoRoT data by Mazeh & Guterman et al. and a phenomenological correction was proposed. Here we tie the observed effect a particular type of effect, and in the process generalize the popular Sysrem algorithm to include external parameters in a simultaneous solution with the unknown effects. We show that a post-processing scheme based on this algorithm performs well and indeed allows for the detection of new transit-like signals that were not previously detected.Comment: MNRAS accepted. 5 pages, 3 figure

Sturgeons in large rivers: detecting the near‑extinct needles in a haystack via eDNA metabarcoding from water samples

Sturgeon populations are declining worldwide and are the target of extensive conservation efforts. Addressed in several pieces of legislation, sturgeons have received considerable attention as flagship or umbrella species. Despite the need for a better understanding of the distribution and population status, the use of traditional sampling methods failed in the past, thereby hampering reliable assessments, a prerequisite for conservation. Here, we describe the development and application of an environmental DNA (eDNA) metabarcoding approach for detecting rare sturgeons in large rivers. Exemplarily, we developed a reference database for five native Danube sturgeons (Acipenser stellatus, Acipenser gueldenstaedtii, Acipenser ruthenus, Acipenser nudiventris, and Huso huso) and two nonnative species (Acipenser baerii and Acipenser transmontanus), assessed these ex situ, and used eDNA as a detection tool along the entire length of the Danube (Europe, ~ 2850 km) and major tributaries. In ex situ analyses, all assays yielded positive amplifications for the assessed sturgeon species. In the Danube, the presence of A. ruthenus was confirmed at 14 of 29 sites (48.3%), and in 2 of 18 tributary sites (11.1%), providing the first comprehensive large-scale biogeographical snapshot of this species. Relative number of reads assigned to A. ruthenus varied between 0 and 2.5%, with sites registering positive detections being clustered in 3 sections of the Danube. Our findings enabled us to confirm the advantages of eDNA monitoring over traditional sampling methods for comprehensive whole-river snapshot studies of sturgeons conducted on a large geographical scale, and therefore we consider it to be a promising approach for application in conservation measures, fisheries management, scientific studies, and adaptive management plans for sturgeons on a global scale