HADES RV Programme with HARPS-N at TNG Perger, M.; García-Piquer, A.; Ribas, I. ...
Astronomy and astrophysics (Berlin),
2/2017, Volume:
598
Journal Article
Context. Targeted spectroscopic exoplanet surveys face the challenge of maximizing their planet detection rates by means of careful planning. For a large planet survey, the number of possible ...observation combinations, i.e., the sequence of observations night after night, both in total time and amount of targets, is enormous. Aims. Sophisticated scheduling tools and the improved understanding of the exoplanet population are employed to investigate an efficient and optimal way to plan the execution of observations. This is applied to the CARMENES instrument, which is an optical and infrared high-resolution spectrograph that has started a survey of about 300 M-dwarf stars in search of terrestrial exoplanets. Methods. We used evolutionary computation techniques to create an automatic scheduler that minimizes the idle periods of the telescope and distributes the observations among all the targets using configurable criteria. We simulated the case of the CARMENES survey with a realistic sample of targets, and we estimated the efficiency of the planning tool both in terms of telescope operations and planet detection. Results. Our scheduling simulations produce plans that use about 99% of the available telescope time (including overheads) and optimally distribute the observations among the different targets. Under such conditions, and using current planet statistics, the optimized plan using this tool should allow the CARMENES survey to discover about 65% of the planets with radial-velocity semi-amplitudes greater than 1 ms-1 when considering only photon noise. Conclusions. The simulations using our scheduling tool show that it is possible to optimize the survey planning by minimizing idle instrument periods and fulfilling the science objectives in an efficient manner to maximize the scientific return.
The Cherenkov Telescope Array (CTA) is the next-generation atmospheric Cherenkov gamma-ray observatory. The Observation Execution System (OES) team within the CTA project is designing and prototyping ...the software to execute the observations and to handle the acquisition of scientific data at GB/s rates. In this contribution we show the OES system as it is being designed using the Unified Modeling Language (UML) and Systems Modeling (SysML) formalisms. In addition, we present the status of the associated prototyping activities.
Real-world problems usually present a huge volume of imprecise data. These types of problems may challenge case-based reasoning systems because the knowledge extracted from data is used to identify ...analogies and solve new problems. Many authors have focused on organizing case memory in patterns to minimize the computational burden and deal with uncertainty. The organization is usually determined by a single criterion, but in some problems, a single criterion can be insufficient to find accurate clusters. This work describes an approach to organize the case memory in patterns based on multiple criteria. This new approach uses the searching capabilities of multiobjective evolutionary algorithms to build a Pareto set of solutions, where each one is a possible organization based on the relevance of objectives. The system shows promising capabilities when it is compared with a successful system based on self-organizing maps. Due to the data set geometry influences, the clustering building process results are analyzed taking into account it. For this reason, some complexity measures are used to categorize data sets according to their topology.
Information system security must battle regularly with new threats that jeopardize the protection of those systems. Security tests have to be run periodically not only to identify vulnerabilities but ...also to control information systems, network devices, services and communications. Vulnerability assessments gather large amounts of data to be further analyzed by security experts, who recently have started using data analysis techniques to extract useful knowledge from these data. With the aim of assisting this process, this work presents CAOS, an evolutionary multiobjective approach to be used to cluster information of security tests. The process enables the clustering of the tested devices with similar vulnerabilities to detect hidden patterns, rogue or risky devices. Two different types of metrics have been selected to guide the discovery process in order to get the best clustering solution: general-purpose and specific-domain objectives. The results of both approaches are compared with the state-of-the-art single-objective clustering techniques to corroborate the benefits of the clustering results to security analysts.
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M ...dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1.
Context. The distribution of exoplanets around low-mass stars is still not well understood. Such stars, however, present an excellent opportunity for reaching down to the rocky and habitable planet ...domains. The number of current detections used for statistical purposes remains relatively modest and different surveys, using both photometry and precise radial velocities, are searching for planets around M dwarfs. Aims. Our HARPS-N red dwarf exoplanet survey is aimed at the detection of new planets around a sample of 78 selected stars, together with the subsequent characterization of their activity properties. Here we investigate the survey performance and strategy. Methods. From 2700 observed spectra, we compare the radial velocity determinations of the HARPS-N DRS pipeline and the HARPS-TERRA code, calculate the mean activity jitter level, evaluate the planet detection expectations, and address the general question of how to define the strategy of spectroscopic surveys in order to be most efficient in the detection of planets. Results. We find that the HARPS-TERRA radial velocities show less scatter and we calculate a mean activity jitter of 2.3 m s-1 for our sample. For a general radial velocity survey with limited observing time, the number of observations per star is key for the detection efficiency. In the case of an early M-type target sample, we conclude that approximately 50 observations per star with exposure times of 900 s and precisions of approximately 1 ms-1 maximizes the number of planet detections.
Nowadays the educational methodologies are being reconsidered to allow the successful achievement of the skills of the future computer engineer. The issue is based on adapting these methodologies ...from the point of view of the competences provided by the subjects. This work in progress focuses on identifying typologies subjects through data mining techniques. This categorization allows experts to study the best way of adapting the educational models in order to guarantee the acquisition of the expected competences.
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