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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.
| Interstellar extinction in the vicinity of the North America and Pelican Nebulae. II
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| The spectra, magnitudes and colours of O-A type stars in an area of the Milky Way, with the Center alpha = 20h16m, delta = +42 D 30'.
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Osservazione e dati astrometrici
| Costellazione: | Cigno |
| Ascensione retta: | 20h30m31.36s |
| Declinazione: | +43°27'48.8" |
| Magnitudine apparente: | 7.596 |
| Distanza: | 423.729 parsec |
| Moto proprio RA: | 3.7 |
| Moto proprio Dec: | -13.1 |
| B-T magnitude: | 7.82 |
| V-T magnitude: | 7.615 |
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