MOBSTER -- III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic 'identical twin'

Abstract

HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M${}_{\odot }$. The primary's longitudinal magnetic field $⟨B_z⟩$ varies between about $+100$ and $-250$ G, suggesting a surface magnetic dipole strength $B_{\mathrm{d}}=850$~G. Bayesian analysis of the Stokes $V$ profiles indicates $B_{\mathrm{d}}=650$~G for the primary and $B_{\mathrm{d}}<110$ G for the secondary. The primary's line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star's chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete.

arXiv comment14 pages, 10 figures, accepted for publication in MNRAS

References in corpus (58)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Transiting Exoplanet Survey Satellite
• Binary interaction dominates the evolution of massive stars
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Astrophysics Source Code Library
• A Computational Guide to Physics of Eclipsing Binaries. Paper I. Demonstrations and Perspectives
• The TESS Input Catalog and Candidate Target List
• The rotation rates of massive stars: the role of binary interaction through tides, mass transfer and mergers
• Observational Constraints on the Formation and Evolution of Binary Stars
• Large-scale magnetic topologies of late M dwarfs
• The Kilodegree Extremely Little Telescope (KELT): A Small Robotic Telescope for Large-Area Synoptic Surveys
• The incidence of stellar mergers and mass gainers among massive stars
• Least squares deconvolution of the stellar intensity and polarization spectra
• Axisymmetric magnetic fields in stars: relative strengths of poloidal and toroidal components
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - I. Observations and measurements
• The MiMeS Survey of Magnetism in Massive Stars: Introduction and overview
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• Collapse of massive magnetized dense cores using radiation-magneto-hydrodynamics: early fragmentation inhibition
• The effect of magnetic fields on star cluster formation
• The KELT-South Telescope
• Rejuvenation of stellar mergers and the origin of magnetic fields in massive stars
• Strong dipole magnetic fields in fast rotating fully convective stars
• Evidence for nonlinear resonant mode coupling in the Beta Cep star HD 180642 (V1449 Aql) from CoRoT space-based photometry
• On the Stability of Non Force-Free Magnetic Equilibria in Stars
• The Magnetic Early B-type Stars III: A main sequence magnetic, rotational, and magnetospheric biography
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• Detection of a weak surface magnetic field on Sirius A: are all tepid stars magnetic ?
• What controls the magnetic geometry of M dwarfs?
• The rapid rotation and complex magnetic field geometry of Vega
• A Volume Limited Survey of mCP Stars Within 100pc II: Rotational and Magnetic Properties
• The global and small-scale magnetic fields of fully convective, rapidly spinning M dwarf pair GJ65A and B
• The KELT Follow-Up Network and Transit False Positive Catalog: Pre-vetted False Positives for TESS
• The magnetic fields of intermediate-mass T Tauri stars : I. Magnetic detections and fundamental stellar parameters
• A Volume-Limited Survey of mCP Stars Within 100pc I: Fundamental Parameters and Chemical Abundances
• Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) - I. First-light observations of known magnetic B and A stars
• A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - II. Rotation
• Magnetic field topologies of the bright, weak-field Ap stars theta Aurigae and epsilon Ursae Majoris
• Weak magnetic fields in early-type stars: failed fossils
• Detection of magnetic fields in both B-type components of the $\epsilon$ Lupi system: a new constraint on the origin of fossil fields?
• Stellar magnetic field parameters from a Bayesian analysis of high-resolution spectropolarimetric observations
• A sudden change of the global magnetic field of the active M dwarf AD Leo revealed by full Stokes spectropolarimetric observations
• Discovery of a very weak magnetic field on the Am star Alhena
• Separating the X-Ray Emissions of UV Ceti A and B with Chandra
• HD 156324: a tidally locked magnetic triple spectroscopic binary with a disrupted magnetosphere
• HD66051: the first eclipsing binary hosting an early-type magnetic star
• The BinaMIcS project: understanding the origin of magnetic fields in massive stars through close binary systems
• Fossil field decay due to nonlinear tides in massive binaries
• HD 99458: First time ever Ap-type star as a $\delta$ Scuti pulsator in a short period eclipsing binary?
• $\epsilon$ Lupi: measuring the heartbeat of a doubly-magnetic massive binary with BRITE-Constellation
• Magnetic field topology of the cool, active, short-period binary system ${\sigma }^2$ Coronae Borealis
• BD-19 5044L: discovery of a short-period SB2 system with a magnetic Bp primary in the open cluster IC 4725
• KELT-22Ab: A Massive Hot Jupiter Transiting a Near Solar Twin
• The origin of magnetic fields in hot stars
• HD 149277: a rare short-period SB2 system with a subsynchronously rotating magnetic He-rich primary

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• NGC 6611 601: A hot pre-main sequence spectroscopic binary containing a centrifugal magnetosphere host star
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