A wealth of information can be inferred from stellar spectra. The effective temperature, surface gravity, projected rotational velocity, and chemical composition can be readily obtained from standard analyses. The classical approach results in errors in effective temperature of about 50 - 100K, and in errors in chemical abundances of about 0.05 dex. However, predicted signatures of planet formation on the host star’s chemical composition demands both precise stellar parameters (effective temperatures within about 10 K) and precise elemental abundances (0.01 dex). This exquisite precision can be achieved by a careful, strict differential analysis between nearly identical stars (stellar twins), as was demonstrated first using solar twins by Melendez et al. (2009) and Ramirez, Melendez & Asplund (2009). Besides being important to study planet signatures (e.g., Ramirez et al. 2011, Tucci Maia et al. 2014, Ramirez et al. 2015, Biazzo et al. 2015), high precision is also key to study stellar evolution (e.g., Monroe et al. 2013; Tucci Maia et al. 2015), star clusters (Yong et al. 2013), and Galactic chemical evolution (e.g., Melendez et al. 2014; Nissen 2015).
The aim of this hands-on workshop is to train a small group of astronomers (~10) on the strict differential technique. We will discuss with the participants all steps necessary to reach precise abundances, including observations, data reduction, equivalent width measurements, line-by-line analysis, stellar parameters, chemical abundances, and determination of errors. The activities will be led by Jorge Melendez (Univ. São Paulo) and Ivan Ramirez (Univ. Texas at Austin), pioneers of the high precision differential technique. Members of our group will help as tutors, and will also present their own work.
During the workshop we will also discuss the different applications of high precision abundances, in particular on planet signatures, but also on the determination of stellar masses and ages, signatures of stellar evolution, and galactic chemical evolution. Members of our group will present different applications, and the participants are welcome to present a talk on their own work.
Line lists, model atmospheres and programs will be provided to the participants, who must bring their own laptop. Sample spectra of solar twins will be also provided to perform a differential abundance analysis, but the participants are encouraged to bring their own data (preferentially of stars similar between them).
Applications will be received until noon GMT, June 18, 2015 (Thursday). The outcome will be released by June 25, 2015. Successful applicants will be required to pay a small registration fee (about 35 euros). Notice that financial aid is not available, but we will organize hotel room sharing.
The workshop will be held at the Universidade de São Paulo (Brazil). For more details see local information.
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