An investigation of the photometric variability of confirmed and candidate Galactic Be stars using ASAS-3 data

Abstract

We present an investigation of a large sample of confirmed (N=233) and candidate (N=54) Galactic classical Be stars (mean V magnitude range of 6.4 to 12.6 mag), with the main aim of characterizing their photometric variability. Our sample stars were preselected among early-type variables using light curve morphology criteria. Spectroscopic information was gleaned from the literature, and archival and newly-acquired spectra. Photometric variability was analyzed using archival ASAS-3 time series data. To enable a comparison of results, we have largely adopted the methodology of Labadie-Bartz et al. (2017), who carried out a similar investigation based on KELT data. Complex photometric variations were established in most stars: outbursts on different time-scales (in 73$\pm$5% of stars), long-term variations (36$\pm$6%), periodic variations on intermediate time-scales (1$\pm$1%) and short-term periodic variations (6$\pm$3%). 24$\pm$6% of the outbursting stars exhibit (semi)periodic outbursts. We close the apparent void of rare outbursters reported by Labadie-Bartz et al. (2017) and show that Be stars with infrequent outbursts are not rare. While we do not find a significant difference in the percentage of stars showing outbursts among early-type, mid-type and late-type Be stars, we show that early-type Be stars exhibit much more frequent outbursts. We have measured rising and falling times for well-covered and well-defined outbursts. Nearly all outburst events are characterized by falling times that exceed the rising times. No differences were found between early-, mid- and late-type stars; a single non-linear function adequately describes the ratio of falling time to rising time across all spectral subtypes, with the ratio being larger for short events.

arXiv comment16 pages main text + 36 pages appendices; 15 figures main text + 6 figures in the appendices; accepted for publication in MNRAS; changes to the previously uploaded version: (a) corrected some typos; (b) repaired broken link to the Shelyak website; (c) deleted a referee comment that accidentally remained in the text at the very end of Section 3.2.4

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