59 research outputs found

    New ground-based observational methods and instrumentation for asteroseismology

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    Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being built to attain very high precision data to be used for asteroseismic analysis. Nonetheless, there is a very strong need for providing additional information, especially on mode identification. With this contribution I will review the efforts been put on new ground-based instrumentation and the methodology that can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar Pulsation Conference Series: Impact of new instrumentation and new insights in stellar pulsations", 5-9 September 2011, Granada, Spai

    Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

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    With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (T_(eff), log g, ξ, and [Fe/H]) by means of the STEPAR code, a PYTHON implementation of the equivalent width method that employs the 2017 version of the MOOG code and a grid of MARCS model atmospheres. We compiled four Fe I and Fe II line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5300 to 17 100 Å, thus substantially increasing the number of identified Fe I and Fe II lines up to 653 and 23, respectively, We examined the impact of the near-infrared Fe and Fen lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gala benchmark stars contained in our sample, Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fe l and Fe II lines when the near-infrared region is taken into account reveals a deeper T_(eff) scale that might stem from a higher sensitivity of the near-infrared lines to T_(eff)

    Understanding the Emergent Structure of Competency Centers in Post-implementation Enterprise Systems

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    Part 3: Structures and NetworksInternational audiencePrior research provides conflicting insights about the link between investment in enterprise systems and firm value and in the ES governance mechanisms. The literature generally suggests that management should cultivate its technical and organizational expertise to derive value from currently deployed Enterprise Systems (ES) [8]. In the realm of practice, ERP vendors and configuration/integration partners strongly recommend the creation of an organizational structure to govern the ERP implementation and post-implementation process to improve project success and extract greater value from the ES investment. The ES literature, while unclear on the formation, and functioning of ES governance units, suggests the need for formal and fixed governance structures. This research utilizes Deleuze’s assemblage theory and emergence theory to explain the genesis and evolution of the governing ‘structure’ known as the Competency Center (CC). Our results illustrate the business needs driving the structuring processes behind the CC, are also those that lead to unintended and destabilizing outcomes. Whether the CC ‘assemblage’ survives to provide value depends on how the emergent issues are handled and how the assemblages are “positioned”. This research suggests effective ES governance is not derived from a prescribed step-wise process yielding formal structures, but rather form an organic process of assemblage

    The CARMENES search for exoplanets around M dwarfs: different roads to radii and masses of the target stars

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    Aims. We determine the radii and masses of 293 nearby, bright M dwarfs of the CARMENES survey. This is the first time that such a large and homogeneous high-resolution (R > 80, 000) spectroscopic survey has been used to derive these fundamental stellar parameters. Methods. We derived the radii using Stefan-Boltzmann’s law. We obtained the required effective temperatures T_(eff) from a spectral analysis and we obtained the required luminosities L from integrated broadband photometry together with the Gaia DR2 parallaxes. The mass was then determined using a mass-radius relation that we derived from eclipsing binaries known in the literature. We compared this method with three other methods: (1) We calculated the mass from the radius and the surface gravity log g, which was obtained from the same spectral analysis as T_(eff). (2) We used a widely used infrared mass-magnitude relation. (3) We used a Bayesian approach to infer stellar parameters from the comparison of the absolute magnitudes and colors of our targets with evolutionary models. Results. Between spectral types M0 V and M7 V our radii cover the range 0.1 Rꙩ < R < 0.6 Rꙩ with an error of 2–3% and our masses cover 0.09 Mꙩ < M < 0.6 Mꙩ with an error of 3–5%. We find good agreement between the masses determined with these different methods for most of our targets. Only the masses of very young objects show discrepancies. This can be well explained with the assumptions that we used for our methods
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