A celestial matryoshka: Dynamical and spectroscopic analysis of the Albireo system

Abstract

We present a spectroscopic characterisation and a new orbital solution for the binary system beta Cyg Aa/Ac (MCA 55), the primary component (beta Cyg A) of the well-known wide double star Albireo. By matching evolutionary tracks to the physical parameters of all three Albireo stars (beta Cyg Aa, Ac and B) as obtained from a spectroscopic analysis of TIGRE and IUE spectra, we confirm that they are likely coeval. Our final orbit solution is based on radial-velocity measurements taken over a baseline exceeding $120$ years, combined with relative astrometry from speckle interferometric observations and the absolute astrometry from the Hipparcos and Gaia missions. Our final orbit solution has a period of $121.65_{-2.90}^{+3.34}$ years with an eccentricity of $0.20_{-0.02}^{+0.01}$. Thanks to the inclusion of the absolute astrometry, we find a mass ratio of $q=1.25_{-0.17}^{+0.19}$, and a total mass of $9.47_{-3.24}^{+5.88}$ M${}_{\odot }$, indicating that the secondary (Ac) is the more massive of the pair. These results strongly suggest the presence of a fourth, unseen, member of the Albireo system. Given the current photometric data it is likely that beta Cyg A is itself a hierarchical triple. We also derive the systemic proper motion, line-of-sight velocity, and an orbital parallax of the beta Cyg A system, allowing us to quantitatively assess the hypothesis that Albireo A and B form a physically bound and genealogically connected system. Finally, we find four potential members of a common proper motion group with Albireo, though none anywhere as close by as the Albireo components A to B.

final draft of accepted manuscript

References in corpus (16)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• EXOFAST: A fast exoplanetary fitting suite in IDL
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Modern stellar spectroscopy caveats
• Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data
• A wide star-black-hole binary system from radial-velocity measurements
• Double-blind test program for astrometric planet detection with Gaia
• A naked-eye triple system with a nonaccreting black hole in the inner binary
• Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting $\pi$ Men
• Detection of the nearest Jupiter analog in radial velocity and astrometry data
• A Model-Independent Mass and Moderate Eccentricity for $\beta$ Pic b
• A precise architecture characterization of the $\pi$ Men planetary system
• A significant mutual inclination between the planets within the $\pi$ Mensae system
• Orbits for eighteen visual binaries and two double-line spectroscopic binaries observed with HRCAM on the CTIO SOAR 4m telescope, using a new Bayesian orbit code based on Markov Chain Monte Carlo
• Magnetic activity and evolution of the four Hyades K giants

Cited by in corpus (6)

• Gaia DR3 astrometric orbit determination with Markov Chain Monte Carlo and Genetic Algorithms. Systems with stellar, substellar, and planetary mass companions
• Results from The COPAINS Pilot Survey: four new brown dwarfs and a high companion detection rate for accelerating stars
• TOI-179: a young system with a transiting compact Neptune-mass planet and a low-mass companion in outer orbit
• On the follow-up efforts of long-period transiting planet candidates detected with Gaia astrometry
• Thirty-Three New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble
• Yet another star in the Albireo system -- The discovery of Albireo Ad