Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


gullingsrud_thesis.pdf (4.81 MB)

ETD Abstract Container

Abstract Header

The Structure of Classical Be Star Decretion Disks

Gullingsrud, Allison Danielle
http://orcid.org/0000-0003-0060-4157
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596758313822129

Abstract Details

2020, Doctor of Philosophy, University of Toledo, Physics.
Be stars are rapidly rotating B stars whose spectra contain Balmer emission lines originating from circumstellar decretion disks. The decretion disks also produce in- frared (IR) excesses in their spectral energy distributions, and the slope of the excess reveals information about the density of the disk. The decretion disks serve as medi- ums through which mass and angular momentum are transported away from the star. Be stars rotate at or near the critical rotation rate, and the angular momentum lost through the disks prevents them from breaking up. Determinations of the amount mass and angular momentum lost through the decretion disks are model dependent. The best accepted model describing the decretion disk is the Viscous Decretion Disk (VDD) model. However, there is a discrepancy between the current measurements of mass-loss rates and those predicted by stellar evolutionary models. The projects in this thesis were chosen to better constrain the models in an effort to reconcile this discrepancy. First, it has been suggested that Be stars are spun up through previous mass- transfer from a binary companion. Also, binary companions are observed to be common. However, the VDD model assumes an isolated Be star. In this thesis, I investigate the density structure of the disks in the presence of binary companions. The Be disk is truncated by the companion, and while most of the disk material accretes onto the binary companion, we find that a portion flows past the binary in what is likely a wind-like outflow. Second, the radiation from the central Be star can launch a line-driven ablation wind that flows radially outward along the surface of the disk. This disk wind is an additional source of mass and angular momentum loss from the central star. I investigate how the disk wind would be observed in the ultraviolet (UV) wind line profiles. I find that the disk wind can be seen as a low velocity narrow absorption component in the UV wind line when the observing geometry is within a few degrees of edge-on.
Jon Bjorkman (Committee Chair)
Alex Carciofi (Committee Member)
Michael Cushing (Committee Member)
Scott Lee (Committee Member)
Tom Megeath (Committee Member)
111 p.
Astronomy; Astrophysics
Be star; Circumstellar Disk; Radiation Transfer; Stellar Winds; Hot Stars

Recommended Citations

Citations

  • Gullingsrud, A. D. (2020). The Structure of Classical Be Star Decretion Disks [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596758313822129

    APA Style (7th edition)

  • Gullingsrud, Allison. The Structure of Classical Be Star Decretion Disks. 2020. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596758313822129.

    MLA Style (8th edition)

  • Gullingsrud, Allison. "The Structure of Classical Be Star Decretion Disks." Doctoral dissertation, University of Toledo, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596758313822129

    Chicago Manual of Style (17th edition)

toledo1596758313822129
382
© 2020, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.
Release 3.2.12