A BRITE view on the massive O-type supergiant V973 Scorpii: hints towards internal gravity waves or sub-surface convection zones
Abstract
Stochastically triggered photospheric light variations reaching ∼40 mmag peak-to-valley amplitudes have been detected in the O8 Iaf supergiant V973 Scorpii as the outcome of 2 months of high-precision time-resolved photometric observations with the BRIght Target Explorer (BRITE) nanosatellites. The amplitude spectrum of the time series photometry exhibits a pronounced broad bump in the low-frequency regime (≲0.9 d-1) where several prominent frequencies are detected. A time-frequency analysis of the observations reveals typical mode lifetimes of the order of 5-10 d. The overall features of the observed brightness amplitude spectrum of V973 Sco match well with those extrapolated from two-dimensional hydrodynamical simulations of convectively driven internal gravity waves randomly excited from deep in the convective cores of massive stars. An alternative or additional possible source of excitation from a sub-surface convection zone needs to be explored in future theoretical investigations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2018
- DOI:
- 10.1093/mnras/sty1897
- arXiv:
- arXiv:1807.04660
- Bibcode:
- 2018MNRAS.480..972R
- Keywords:
-
- convection;
- waves;
- techniques: photometric;
- stars: massive;
- supergiants;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 17 pages, 12 figures, 3 tables