Searching for Earth-mass planets around α\alpha Centauri: precise radial velocities from contaminated spectra

This work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system $\alpha$ Centauri using the Doppler method. Owing to the small angular separation between the two components of the $\alpha$ Cen AB binary system, the observations will to some extent be contaminated with light coming from the other star. We are accurately determining the amount of contamination for every observation by measuring the relative strengths of the H-$\alpha$ and NaD lines. Furthermore, we have developed a modified version of a well established Doppler code that is modelling the observations using two stellar templates simultaneously. With this method we can significantly reduce the scatter of the radial velocity measurements due to spectral cross-contamination and hence increase our chances of detecting the tiny signature caused by potential Earth-mass planets. After correcting for the contamination we achieve radial velocity precision of $\sim 2.5\,\mathrm{m\,s^{-1}}$ for a given night of observations. We have also applied this new Doppler code to four southern double-lined spectroscopic binary systems (HR159, HR913, HR7578, HD181958) and have successfully recovered radial velocities for both components simultaneously.Comment: accepted for publication in the International Journal of Astrobiology (published by Cambridge University Press); will appear in a revised form, subsequent to editorial input by Cambridge University Pres

Division IX: Optical and infrared techniques

This document introduces the reports by the Commissions and Working Groups of Division IX. © 2007 International Astronomical Union

The interstellar medium towards the Ara OB1 region

We present high resolution (R ~ 4 km/s) absorption measurements of the interstellar NaI and CaII lines measured towards 14 early-type stars of distance 123 pc - 1650 pc, located in the direction of the Ara OB1 stellar cluster. The line profiles can broadly be split into four distinct groupings of absorption component velocity, and we have attempted to identify an origin and distance to each of these interstellar features. For gas with absorption covering the velocity range -10 km/s < V_helio < +10 km/s, we can identify the absorbing medium with local gas belonging to the Lupus-Norma interstellar cavity located between 100 and 485 pc in this galactic direction. Gas with velocities spanning the range -20 km/s < V_helio < +20 km/s is detected towards stars with distances of 570-800 pc. We identify a wide-spread interstellar feature at V_helio ~ -15 km/s with the expanding HI shell called GSH 337+00-05, which is now placed at a distance of ~530 pc.Comment: 12 pages, 5 figures, accepted for publication in Astrophysics & Space Scienc

The analysis of starlight: two centuries of astronomical spectroscopy

A reference for astronomers and historians on astronomical spectroscopy, from the discovery of spectral lines through to the year 2000

Special Session 5: Astronomy for the developing world

The International Astronomical Union has a strong commitment to the development of astronomical education and research throughout the world, especially in those countries developing economically. This commitment is in part through the work of IAU Commission 46 for astronomy education and development. Within that commission, the Program Group for the World-wide Development of Astronomy (PGWWDA) coordinates many of these activities, promoting the development of astronomy in developing countries. Six years ago, at the time of the IAU XXIV General Assembly in Manchester, Alan Batten, who was then chair of the PGWWDA, organized a special session on ‘Astronomy for developing countries’ (A. Batten. ed., 2001, Astronomy for Developing Countries, Proc. IAU XXIV GA Special Session (San Francisco: ASP). The success of that meeting has led Commission 46 to propose another Special Session, this time at the IAU XXVI General Assembly, in Prague, 2006. These pages present highlights from that two-day session, known as Special Session 5 on Astronomy for the Developing World

Spectroscopic orbits for K giants betabeta Reticuli and nunu Octantis: what is causing a low-amplitude radial velocity resonant perturbation in nunu Oct?

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