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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.
| Observational stability in AM stars
Differential photoelectric photometry is carried out in metallic-linestars suspected of variability and in the pulsating Am: star HR 8210.The pulsational stability of classical Am stars is confirmed and thehypothesis that the Am phenomenon is the result of diffuse elementseparation is still consistent with the observations. The variability ofHR 8210 is confirmed too. The behavior of this star should beinterpreted as evidence of a multiple-period structure.
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Observation and Astrometry data
| Constellation: | Lyra |
| Right ascension: | 19h11m37.71s |
| Declination: | +26°16'42.8" |
| Apparent magnitude: | 7.767 |
| Distance: | 309.598 parsecs |
| Proper motion RA: | -2.3 |
| Proper motion Dec: | -5.3 |
| B-T magnitude: | 7.734 |
| V-T magnitude: | 7.765 |
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