HD 183986: A High-contrast SB2 System with a Pulsating Component

• Published in: The Astronomical journal Vol. 163; no. 6; pp. 245 - 258
• Main Authors: Vaňko, Martin, Pribulla, Theodor, Gajdoš, Pavol, Budaj, Ján, Zverko, Juraj, Paunzen, Ernst, Garai, Zoltán, Hambálek, Lubomír, Komžík, Richard, Kundra, Emil
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01-06-2022; IOP Publishing
• Subjects: Astronomy; Binary stars; Extrasolar planets; Line spectra; Orbits; Parameters; Photometric observations; Photometry; Physical properties; Planet detection; Pulsating variable stars; Radial velocity; Spectra; Stellar rotation; Transit; Variability
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/ac617b

There is a small group of peculiar early-type stars on the main sequence that show different rotation velocities from different spectral lines. This inconsistency might be due to the binary nature of these objects. We aim to verify this hypothesis by a more detailed spectroscopic and photometric investigation of one such object: HD 183986. We obtained 151 high- and medium-resolution spectra that covered an anticipated long orbital period. There is clear evidence of the orbital motion of the primary component. We uncovered a very faint and broad spectrum of the secondary component. The corresponding SB2 orbital parameters, and the component spectra, were obtained by Fourier disentangling using the
KOREL
code. The component spectra were further modeled by
iSpec
code to arrive at the atmospheric quantities and the projected rotational velocities. We have proven that this object is a binary star with a period
P
= 1268.2(11) days, eccentricity
e
= 0.5728(20), and mass ratio
q
= 0.655. The primary component is a slowly rotating star (
v
sin
i
=
27
km s
−1
) while the cooler and less massive secondary rotates much faster (
v
sin
i
∼
120 km s
−1
). Photometric observations obtained by the Transiting Exoplanet Survey Satellite (TESS) satellite were also investigated to shed more light on this object. A multiperiod photometric variability was detected in the TESS data ranging from hours (the
δ
Sct-type variability) to a few days (spots/rotational variability). The physical parameters of the components and the origin of the photometric variability are discussed in more detail.