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Newly discovered active binaries in the RasTyc sample of stellar X-ray sources. I. Orbital and physical parameters of six new binaries
We present the first results from follow-up optical observations, bothphotometric and spectroscopic, of stellar X-ray sources, selected fromthe RasTyc sample, resulting from the cross-correlation of ROSAT All-SkySurvey (RASS) and TYCHO catalogues. In particular, we report on thediscovery of six late-type binaries, for which we obtained good radialvelocity curves and solved their orbits. We performed an automaticspectral classification of both single-lined and double-lined binarieswith codes developed by us and found two binaries composed of twomain-sequence stars and four binaries with an evolved (giant orsubgiant) component. Filled-in or pure emission Hα profilesindicative of a moderate or high level of chromospheric activity wereobserved. In nearly all the systems, we also detected a photometricmodulation ascribable to surface inhomogeneities that is correlated withthe orbital period, suggesting a synchronization between rotational andorbital periods. The position on the HR diagram of the components of thefive sources with a known parallax indicates three binaries containingonly main-sequence stars and two single-lined systems with a giantcomponent. The kinematical properties of two, or possibly four, of theobserved systems are consistent with a young disk population.
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A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJS....2..298M&db_key=AST
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Member of following groups:
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Observation and Astrometry data
| Constellation: | Giraffe |
| Right ascension: | 04h05m42.34s |
| Declination: | +57°07'37.0" |
| Apparent magnitude: | 9.075 |
| Proper motion RA: | -16.4 |
| Proper motion Dec: | -4.3 |
| B-T magnitude: | 10.446 |
| V-T magnitude: | 9.189 |
Catalogs and designations:
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