The Great Dimming of the Hypergiant Star RW Cephei: CHARA Array Images and Spectral Analysis
Abstract
The cool hypergiant star RW Cephei is currently in a deep photometric minimum that began several years ago. This event bears a strong similarity to the Great Dimming of the red supergiant Betelgeuse that occurred in 2019-2020. We present the first resolved images of RW Cephei that we obtained with the CHARA Array interferometer. The angular diameter and Gaia distance estimates indicate a stellar radius of 900-1760 R ⊙, which makes RW Cephei one of the largest stars known in the Milky Way. The reconstructed, near-infrared images show a striking asymmetry in the disk illumination with a bright patch offset from the center and a darker zone to the west. The imaging results depend on assumptions made about the extended flux, and we present two cases with and without allowing extended emission. We also present a recent near-infrared spectrum of RW Cep that demonstrates that the fading is much larger at visual wavelengths compared to that at near-infrared wavelengths as expected for extinction by dust. We suggest that the star's dimming is the result of a recent surface mass ejection event that created a dust cloud that now partially blocks the stellar photosphere.
- Publication:
-
The Astronomical Journal
- Pub Date:
- August 2023
- DOI:
- 10.3847/1538-3881/ace59d
- arXiv:
- arXiv:2307.04926
- Bibcode:
- 2023AJ....166...78A
- Keywords:
-
- Late-type supergiant stars;
- Stellar mass loss;
- Stellar radii;
- Variable stars;
- 910;
- 1613;
- 1626;
- 1761;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 20 pages, accepted for AJ