Newly discovered active binaries in the RasTyc sample of X-ray stellar sources
Antonio Frasca (INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, I--95123 Catania, ITALY)
Patrick Guillout (Observatoire Astronomique de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, FRANCE)
Ettore Marilli (INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, I--95123 Catania, ITALY)
The cross-correlation between the ROSAT all-sky survey (150,000 sources) and the Tycho mission
(1,000,000 stars) catalogues has selected about 14,000 stellar X-ray sources (RasTyc sample, Guillout et al. 1999).
About 300 stars have been spectroscopically observed
at high resolution both in H-alpha and LiI-6708
regions with Elodie and Aurelie spectrographs of the OHP (Observatoire de l'Haute Provence, France) with the aim of classify the stars of the RasTyc sample
in the northern hemisphere in terms of age, rotation rate and chromospheric activity level and to detect eventual binary systems.
In this work we present preliminary results of follow-up observations, both photometric and spectroscopic, of a RasTyc sub-sample performed
with the 91-cm telescope of the Catania Astrophysical Observatory, Italy.
In particular, we have discovered and studied a few late-type binaries, obtaining good radial velocity curves and solving for the orbits. Filled-in or emission H-alpha profiles have been observed.
We have also detected, in some cases, a photometric
modulation ascribable to photospheric surface inhomogeneities and chromospheric H-alpha line variation.
References
- Guillout, P., Schmitt, J. H. M. M., Egret, D., Voges, W., Motch, C.,
& Sterzik, M. F. 1999, A&A 351, 1003
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