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The Photometric Variability of AE and A-Shell Stars
Though the Herbig Ae stars are known to be photometrically variable, thebehavior of non-PMS Ae and A-shell stars has not been well-studied,chiefly because they are not numerous. This paper reports on the BVphotometric behavior of 41 Ae and A-shell stars. Additionally, 48 coudespectra at H- alpha of 16 of these objects have been studied. It hasbeen found that 39% of the stars are variable in V mag. There are 3types of variation: long cycle, short cycle (about an essentially stablemean), and flare-like. Most variables are short cycle, with B-V colorchanges in opposite direction to V changes. The average V range fornon-flare-like stars is 0.223 V mags, .160 B-V mags. V and B-V rangesare related, in that the largest V range stars have the largest B-Vranges. The largest V ranges belong to the flare-like stars, with thesmallest being short cycle variables. Photometric variation occurs onlyin spectral types <=A5, with short cycle variation only occurring instars <=A2. The stronger the emission at H-alpha, the more likely thestar is to vary, while stars with strong H-alpha shell lines arenon-variable. No emission at H-alpha was observed in stars >A3. Theearliest stars also possessed the strongest shells. Most stars hadtemporally stable spectra. The flare-like A stars comprise a class ofthree: HD 38451, BD+47 819 (both having had flares reported in theliterature), and HDE 229189. The latter star was observed to have V andB-V ranges of 1.592 and 1.653 mags respectively. The flares areinfrequent but rapid in onset, subside quickly, and are accompanied bysubstantial increases in H-alpha emission.
| UBV corrections for bright stars in SIMBAD
Not Available
| UBV photometry of stars whose positions are accurately known. VI
Results are presented from UBV photometric observations of 1000 stars ofthe Bright Star Catalogue and the faint extension of the FK5.Observations were carried out between July 1987 and December 1990 withthe 40-cm Cassegrain telescope of the Kvistaberg Observatory.
| HD 38452 - J. R. Hind's star that changed colour
In 1851, John Russell Hind announced that a star previously observed byhim to be very red had become bluish white in color. It is shown thatthis star, HD 38451, is a ninth magnitude shell star which presumablywas ejecting a shell when Hind first observed it. From high dispersioncoude spectra, low dispersion IUE spectra, and ground-based photometry,HD 38451 is found to be a normal A21V shell star. Its current values ofE(B-V) of about 0.14 is probably caused by interstellar rather thancircumstellar reddening. There remains a problem to reconcile the largeamount of reddening present when Hind first observed the star with itsevidently small diminution in visual brightness at that time.
| Spectral Classifications for 112 Variable Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960ApJ...131..632H&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Bika |
| Rektaszcenzió: | 05h46m45.09s |
| Deklináció: | +21°12'01.2" |
| Vizuális fényesség: | 8.831 |
| RA sajátmozgás: | -3.2 |
| Dec sajátmozgás: | -11.2 |
| B-T magnitude: | 9.102 |
| V-T magnitude: | 8.854 |
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