Toward Understanding the B[e] Phenomenon. IX. Nature and Binarity of MWC645
Abstract
We present the results of optical and near-IR spectroscopy and multicolor photometry of the emission-line star MWC 645, which exhibits the B[e] phenomenon. The presence of positionally variable absorption lines of a cool star detected for the first time indicates that the object is a binary system. Using a combination of the photometric and spectroscopic data as well as the Gaia EDR3 distance (D = 6.5 ± 0.9 kpc), we disentangled the components' contributions and estimated their surface temperatures and luminosities (18, 000 ± 2000 K and 4250 ± 250 K, log L/L ⊙ = 4.0 ± 0.5 and 3.1 ± 0.3 for the hot and cool components, respectively). Quasi-cyclic short-period (months) and long-period (~4 yr) photometric variations were detected in both optical and near-IR regions, and are most likely due to variable circumstellar extinction. Our analysis suggests that MWC 645 is a member of the FS CMa group. The object's properties can be described by an evolutionary model of a close binary system that currently undergoes a nonconservative mass transfer between intermediate-mass stars (e.g., 7 M ⊙ + 2.8 M ⊙).
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2022
- DOI:
- 10.3847/1538-4357/ac87a1
- Bibcode:
- 2022ApJ...936..129N
- Keywords:
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- A stars;
- Binary stars;
- Spectroscopic binary stars;
- Be stars;
- Emission line stars;
- 5;
- 154;
- 1557;
- 142;
- 460