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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.
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The results of a survey of 153 active-chromosphere stars made with theParkes 64-m telescope at 5.0/8.4 GHz from 1981 to 1987 are reported.Microwave emission was detected from 70 stars on at least one occasion,with the highest detection rate of 68 percent from the RS CVn group. TheCa II stars and Algol-type binaries yielded detection rates of 44 and 30percent, respectively. The maximum powers emitted by the stars at5.0/8.4 GHz ranged over five orders of magnitude, with a median of 2.5 x10 to the 10th W/Hz. The maximum brightness temperatures had a smallerrange of three orders of magnitude, with a median of 3.6 x 10 to the 9thK.
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| New Bright Southern Variable Stars
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Osservazione e dati astrometrici
| Costellazione: | Tucano |
| Ascensione retta: | 22h38m35.69s |
| Declinazione: | -63°34'21.4" |
| Magnitudine apparente: | 8.992 |
| Distanza: | 413.223 parsec |
| Moto proprio RA: | 22.5 |
| Moto proprio Dec: | -22.6 |
| B-T magnitude: | 10.184 |
| V-T magnitude: | 9.091 |
Cataloghi e designazioni:
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