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HD 217875


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The influence of the envelope in the variations of transitory type Be stars
The contribution of the stellar envelope to variations oftransitory-type Be stars, which are alternately of types B and Be, isinvestigated. The Rojas-Herman classification is applied to thequantification of long-term stellar variation for a sample of Be starsbrighter than magnitude 7, and compared with the spectral properties ofthese stars. A relation is derived between the equivalent widths of theH-alpha and H-beta lines and the stellar U-B index. The U-B index isthen calibrated as a function of the Balmer discontinuity in order toseparate the contributions of the star and its envelope to the emission.The separate U-B indices derived for the star, which are characterizedby long-term variations, and the envelope, which is sensitive toshort-term variations, are observed to be additive, implying that theobserved flux is a convolution of the fluxes emitted by the star and itsenvelope.

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Osservazione e dati astrometrici

Costellazione:Pesci
Ascensione retta:23h03m46.20s
Declinazione:+07°20'04.1"
Magnitudine apparente:8.796
Moto proprio RA:-12.2
Moto proprio Dec:0.8
B-T magnitude:9.395
V-T magnitude:8.846

Cataloghi e designazioni:
Nomi esatti   (Edit)
HD 1989HD 217875
TYCHO-2 2000TYC 582-35-1
USNO-A2.0USNO-A2 0900-20306140

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