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HD 189436


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The photometric variability of solar-type stars. II - Stars selected from Wilson's chromospheric activity survey
Eleven solar-type main-sequence stars have been observed to search forcontinuum variability. Stars were selected from Wilson's chromosphericactivity survey, and were observed for periods of three to six monthswith intermediate-band Stroemgren uvby photometry. Evidence is foundthat two of these eleven stars are variable and that one other may be.Comparison with contemporaneous Ca II H + K emission flux measurementsshows that the amplitude of photometric variability correlates stronglywith both the mean emission flux and the amplitude of its variation.Variations in continuum light and emission flux tend to correlate intime, as well, with continuum minima coinciding with emission maxima andvice-versa. It is inferred that the surface activity of these starstends to be confined to localized activity centers that include bothemission plages and dark spots, similar to the active regions observedon the sun.

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Observation and Astrometry data

Constellation:Aquila
Right ascension:19h59m57.04s
Declination:+04°26'18.4"
Apparent magnitude:8.609
Proper motion RA:47.3
Proper motion Dec:-5.9
B-T magnitude:9.141
V-T magnitude:8.653

Catalogs and designations:
Proper Names
HD 1989HD 189436
TYCHO-2 2000TYC 489-2009-1
USNO-A2.0USNO-A2 0900-17354092

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