Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...185.4822h&link_type=abstract
American Astronomical Society, 185th AAS Meeting, #48.22; Bulletin of the American Astronomical Society, Vol. 26, p.1391
Astronomy and Astrophysics
Astronomy
Scientific paper
Though the Herbig Ae stars are known to be photometrically variable, the behavior of non-PMS Ae and A-shell stars has not been well-studied, chiefly because they are not numerous. This paper reports on the BV photometric behavior of 41 Ae and A-shell stars. Additionally, 48 coude spectra at H- alpha of 16 of these objects have been studied. It has been found that 39% of the stars are variable in V mag. There are 3 types of variation: long cycle, short cycle (about an essentially stable mean), and flare-like. Most variables are short cycle, with B-V color changes in opposite direction to V changes. The average V range for non-flare-like stars is 0.223 V mags, .160 B-V mags. V and B-V ranges are related, in that the largest V range stars have the largest B-V ranges. The largest V ranges belong to the flare-like stars, with the smallest being short cycle variables. Photometric variation occurs only in spectral types <=A5, with short cycle variation only occurring in stars <=A2. The stronger the emission at H-alpha, the more likely the star is to vary, while stars with strong H-alpha shell lines are non-variable. No emission at H-alpha was observed in stars >A3. The earliest stars also possessed the strongest shells. Most stars had temporally stable spectra. The flare-like A stars comprise a class of three: HD 38451, BD+47 819 (both having had flares reported in the literature), and HDE 229189. The latter star was observed to have V and B-V ranges of 1.592 and 1.653 mags respectively. The flares are infrequent but rapid in onset, subside quickly, and are accompanied by substantial increases in H-alpha emission.
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