Classifying the secondary component of the binary star W Aquilae

Abstract

AIMS: The object W Aql is an asymptotic giant branch (AGB) star with a faint companion. By determining more carefully the properties of the companion, we hope to better constrain the properties of the AGB star. METHODS: We present new spectral observations of the binary star W Aql at minimum and maximum brightness and new photometric observations of W Aql at minimum brightness. RESULTS: The composite spectrum near minimum light is predominantly from the companion at wavelengths $\lambda$ < 6000 $\mathring{A}$. This spectrum can be classified as F8 to G0, and the brightness of the companion is that of a dwarf star. Therefore, it can be concluded that the companion is a main sequence star. From this, we are able to constrain the mass of the AGB component to 1.04 - 3 $M_{\odot }$ and the mass of the W Aql system to 2.1 - 4.1 $M_{\odot }$ . Our photometric results are broadly consistent with this classification and suggest that the main sequence component suffers from approximately 2 mag of extinction in the V band primarily due to the dust surrounding the AGB component.

arXiv comment5 pages, 1 figure, research note

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• The circumstellar envelope around the S-type AGB star W Aql Effects of an eccentric binary orbit
• The VLT/SPHERE view of the ATOMIUM cool evolved star sample. I. Overview: Sample characterization through polarization analysis
• The surprisingly carbon-rich environment of the S-type star W Aql
• Chemical tracers of a highly eccentric AGB-main sequence star binary
• An accreting dwarf star orbiting the S-type giant star pi1 Gru
• ATOMIUM: Continuum emission and evidence of dust enhancement from binary motion
• Morphology and kinematics of the gas envelope of the Mira binary W Aquilae