Improved model of the triple system V746 Cas that has a bipolar magnetic field associated with the tertiary

Abstract

V746 Cas is known to be a triple system composed of a close binary with an alternatively reported period of either 25.4d or 27.8d and a third component in a 62000d orbit. The object was also reported to exhibit multiperiodic light variations with periods from 0.83d to 2.50d, on the basis of which it was classified as a slowly pulsating B star. Interest in further investigation of this system was raised by the detection of a variable magnetic field. Analysing spectra from four instruments, earlier published radial velocities, and several sets of photometric observations, we arrived at the following conclusions: (1) The optical spectrum is dominated by the lines of the B-type primary (Teff1~16500(100) K), contributing 70% of the light in the optical region, and a slightly cooler B tertiary (Teff3~13620(150) K). The lines of the low-mass secondary are below our detection threshold; we estimate that it could be a normal A or F star. (2) We resolved the ambiguity in the value of the inner binary period and arrived at a linear ephemeris of T_super.conj.=HJD 2443838.78(81)+25.41569(42)xE. (3) The intensity of the magnetic field undergoes a~sinusoidal variation in phase with one of the known photometric periods, namely 2.503867(19)d, which we identify with the rotational period of the tertiary. (4) The second photometric 1.0649524(40)d period is identified with the rotational period of the B-type primary, but this interpretation is much less certain and needs further verification. (5) If our interpretation of photometric periods is confirmed, the classification of the object as a slowly pulsating B star should be revised. (6) Applying an N-body model to different types of available observational data, we constrain the orbital inclination of the inner orbit to ~60 deg to 85 deg even in the absence of eclipses, and estimate the probable properties of the triple system and its components.

arXiv commentAccepted for publication in Astronomy and Astrophysics

References in corpus (19)

• emcee: The MCMC Hammer
• Validation of the new Hipparcos reduction
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• A Computational Guide to Physics of Eclipsing Binaries. Paper I. Demonstrations and Perspectives
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• The rotation rates of massive stars: the role of binary interaction through tides, mass transfer and mergers
• The High Angular Resolution Multiplicity of Massive Stars
• A spectroscopic survey on the multiplicity of high-mass stars
• The ELODIE archive
• Rotation periods of 12 000 main-sequence Kepler stars: Dependence on stellar spectral type and comparison with v sin i observations
• The MiMeS Survey of Magnetism in Massive Stars: Introduction and overview
• PolarBase: a data base of high resolution spectropolarimetric stellar observations
• POLLUX : a database of synthetic stellar spectra
• The Classificiation of Kepler B star Variables
• Variability of Massive Stars with Known Spectral Types in the Small Magellanic Cloud Using 8 Years of OGLE-III Data
• A Spectroscopic Study of Field and Runaway OB Stars
• Discovery of a magnetic field in the B pulsating system HD 1976
• An advanced N-body model for interacting multiple stellar systems

Cited by in corpus (2)

• Analysis of apsidal motion in eclipsing binaries using TESS data II. A test of internal stellar structure}
• ARMADA II: Further Detections of Inner Companions to Intermediate Mass Binaries with Micro-Arcsecond Astrometry at CHARA and VLTI