Bibliographic Details
| Title: |
The Hubble Space Telescope Advanced Camera for Surveys Emission Line Survey of Andromeda. I: Classical Be Stars |
| Authors: |
Peters, M., Wisniewski, J. P., Williams, B. F., Lomax, J. R., Choi, Y., Durbin, M., Johnson, L. C., Lewis, A. R., Lutz, J., Sigut, T. A. A., Wallach, A., Dalcanton, J. J. |
| Publication Year: |
2019 |
| Collection: |
Astrophysics |
| Subject Terms: |
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies |
| More Details: |
We present results from a 2-epoch HST H$\alpha$ emission line survey of the Andromeda Galaxy that overlaps the footprint of the Panchromatic Hubble Andromeda Treasury (PHAT) survey. We find 552 (542) classical Be stars and 8429 (8556) normal B-type stars in epoch # 1 (epoch # 2), yielding an overall fractional Be content of 6.15% $\pm$0.26% (5.96% $\pm$0.25%). The fractional Be content decreased with spectral sub-type from $\sim$23.6% $\pm$2.0% ($\sim$23.9% $\pm$2.0%) for B0-type stars to $\sim$3.1% $\pm$0.34% ($\sim$3.4% $\pm$0.35%) for B8-type stars in epoch # 1 (epoch # 2). We observe a clear population of cluster Be stars at early fractional main sequence lifetimes, indicating that a subset of Be stars emerge onto the ZAMS as rapid rotators. Be stars are 2.8x rarer in M31 for the earliest sub-types compared to the SMC, confirming that the fractional Be content decreases in significantly more metal rich environments (like the Milky Way and M31). However, M31 does not follow a clear trend of Be fraction decreasing with metallicity compared to the Milky Way, which may reflect that the Be phenomenon is enhanced with evolutionary age. The rate of disk-loss or disk-regeneration episodes we observe, 22% $\pm$ 2% yr$^{-1}$, is similar to that observed for seven other Galactic clusters reported in the literature, assuming these latter transient fractions scale by a linear rate. The similar number of disk-loss events (57) as disk-renewal events (43) was unexpected since disk dissipation time-scales can be $\sim$2x the typical time-scales for disk build-up phases.
Comment: Accepted to AJ |
| Document Type: |
Working Paper |
| DOI: |
10.3847/1538-3881/ab6d74 |
| Access URL: |
http://arxiv.org/abs/1912.05627 |
| Accession Number: |
edsarx.1912.05627 |
| Database: |
arXiv |
