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Inaccuracies in the spectral classification of stars from the Tycho-2 Spectral Type Catalogue
We compare the spectroscopic and trigonometric parallaxes of commonstars from the Tycho-2 Spectral Type and Hipparcos Catalogues. Thiscomparison has revealed that the distance estimations for theoverwhelming majority of stars by both methods yield very similarresults. However, there is a small fraction of stars for which thedistance estimates differ significantly. It is these stars that are thesubject of our study. We have been able to find the causes of thesedifferences.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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Osservazione e dati astrometrici
| Costellazione: | Sagittario |
| Ascensione retta: | 19h31m25.11s |
| Declinazione: | -13°58'41.2" |
| Magnitudine apparente: | 8.746 |
| Distanza: | 182.149 parsec |
| Moto proprio RA: | 18.8 |
| Moto proprio Dec: | -6.5 |
| B-T magnitude: | 10.559 |
| V-T magnitude: | 8.896 |
Cataloghi e designazioni:
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