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SD1000 Collaboration

Aims: The primary goal of the SD1000 Collaboration is to collect and process medium to high-resolution, high signal-to-noise optical spectra for about 1000 hot subdwarf stars and publish results from their homogeneous model atmosphere analysis. The Collaboration will derive accurate atmospheric parameters for both sdB and sdO subdwarf populations. Thanks to the large sample, this analysis may provide important observational constraints for subdwarf formation, evolution and pulsation theories.

Method: The Subdwarf Database contains about 1150 stars brighter than V=16 magnitudes, providing a rich source of bright subdwarfs that are easily accessible on 4-m telescopes. However, recording new, high-quality data for 1000 stars would require 60-80 nights, what is not practically feasible. Acquiring data from public archives could be a way, although, data reduction of various observing runs can introduce a significant overhead and not all data are available in such archives. Morevover, it is important to maximize the number of spectra to number of instruments ratio to decrease instrumental biases in the sample. The most efficient strategy would use contributed data for the bulk and obtain new observations for a small subset to fill the sample. Therefore, the success of this project depends on the amount of contributed data and we look for collaborators. We estimate that enough observations have been taken over the last 30 years to compile the target sample with ease. A model atmosphere analysis will be done with TLUSTY/SYNSPEC and the XTGRID spectral fitting program. In the first stage of the programme we apply H, He, C and N models with single star models. This stage will be finished in a month. In the second stage, we apply H, He, C, N, O, Ne, Mg, Si, P, S, Fe and Ni composition. The distributed calculations on the 24-core MAIDS cluster should take about ten months. Binary decomposition will be included where necessary, about 20% of sdB stars show double-lined composite spectra. The results will be published in refereed journals and a catalog will be made available similarly to our GALEX catalog.

State: The project is currently pending, we welcome collaborators who can contribute observations to the target sample. Meanwhile we are woking on reducing the systematic biases that arise from inhomogeneous observations. Funding is available until 2016.

    Stephan Geier (University of Tubingen)
    Ulrich Heber (Dr Remeis Observatory, Bamberg)
    Adela Kawka (Ondřejov Observatory)
    Roy H. Østensen (KU Leuven)
    Stephane Vennes (Ondřejov Observatory)

Data Submission

Please provide wavelength calibrated arcs that were used for the dispersion solution for each observation! These will be used to describe the variation of spectral resolution along the dispersion axis.

Stay tuned, it's coming soon!