http://arxiv.org/abs/1708.02594
In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the APOGEE survey and BeSS database for a sample of 160 Galactic classical Be stars. The systems studied here show variability including transitions from a disk-less to a disk-possessing state (and vice versa), and persistent disks that vary in strength, being replenished at either regularly or irregularly occurring intervals. We detect disk-building events (outbursts) in the light curves of 28\% of our sample. Outbursts are more commonly observed in early- (57\%), compared to mid- (27\%) and late-type (8\%) systems. A given system may show anywhere between 0 — 40 individual outbursts in its light curve, with amplitudes ranging up to $\sim$0.5 mag and event durations between $\sim$2 — 1000 days. The duration of disk build-up and dissipation phases are measured for 66 outbursts, and we find a median build-up time of 8.8 days, and a median dissipation time of 17.1 days. This analysis also suggests that the disks of late-type systems take longer to dissipate, compared to their hotter counterparts. We study how both the photometry and spectroscopy change together during active episodes of disk growth or dissipation, revealing details about the evolution of the circumstellar environment. We demonstrate that photometric activity is linked to changes in the inner disk, and show that, at least in some cases, the disk growth process is asymmetrical. Observational evidence of Be star disks both growing and clearing from the inside out is presented.
J. Labadie-Bartz, S. Chojnowski, D. Whelan, et. al.
Thu, 10 Aug 17
17/39
Comments: 20 pages, 24 figures, 2 tables; submitted to AAS journals