A Comprehensive Analysis of the Magnetic Standard Star HD 94660: Host of a Massive Compact Companion?

Abstract

Detailed information about the magnetic geometry, atmospheric abundances and radial velocity variations has been obtained for the magnetic standard star HD 94660 based on high-dispersion spectroscopic and spectropolarimetric observations from the UVES, HARPSpol and ESPaDOnS instruments. We perform a detailed chemical abundance analysis using the spectrum synthesis code zeeman for a total of 17 elements. Using both line-of-sight and surface magnetic field measurements, we derive a simple magnetic field model that consists of dipole, quadrupole and octupole components. The observed magnetic field variations of HD 94660 are complex and suggest an inhomogeneous distribution of chemical elements over the stellar surface. This inhomogeneity is not reflected in the abundance analysis, from which all available spectra are modelled, but only a mean abundance is reported for each element. The derived abundances are mostly non-solar, with striking overabundances of Fe-peak and rare-earth elements. Of note are the clear signatures of vertical chemical stratification throughout the stellar atmosphere, most notably for the Fe-peak elements. We also report on the detection of radial velocity variations with a total range of 35 km/s in the spectra of HD 94660. A preliminary analysis shows the most likely period of these variations to be of order 840 d and, based on the derived orbital parameters of this star, suggests the first detection of a massive compact companion for a main sequence magnetic star. HD 94660 exhibits interestingly complex magnetic field variations and remarkable radial velocity variations. Long term monitoring is necessary to provide further constraints on the nature of these radial velocity variations. Detection of a companion will help establish the role of binarity in the origin of magnetism in stars with radiative envelopes.

arXiv comment12 pages, Accepted for publication in A&A

References in corpus (17)

• The chemical composition of the Sun
• Validation of the new Hipparcos reduction
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Magnetic fields of non-degenerate stars
• Least squares deconvolution of the stellar intensity and polarization spectra
• Searching for links between magnetic fields and stellar evolution. II. The evolution of magnetic fields as revealed by observations of Ap stars in open clusters and associations
• Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1
• Searching for links between magnetic fields and stellar evolution III. Measurement of magnetic fields in open cluster Ap stars with ESPaDOnS
• The search for magnetic fields in mercury-manganese stars
• On the consistency of magnetic field measurements of Ap stars: lessons learned from the FORS1 archive
• Abundances determined using Si II and Si III in B-type stars: evidence for stratification
• Discovery of secular variations in the atmospheric abundances of magnetic Ap stars
• Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712 I. Spectropolarimetric observations in all four Stokes parameters
• A self consistent chemically stratified atmosphere model for the roAp star 10 Aquilae
• An Analysis of the Rapidly Rotating Bp Star HD 133880
• Magnetic Field and Atmospheric Chemical Abundances of the Magnetic Ap Star HD 318107
• Measuring the surface magnetic fields of magnetic stars with unresolved Zeeman splitting

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• Searching for a magnetic field in Wolf-Rayet stars using FORS2 spectropolarimetry
• A Magnetic White Dwarf with Five H$\alpha$ Components
• Discovery and origin of the radio emission from the multiple stellar system KQVel
• Chandra's X-ray study confirms that the magnetic standard Ap star KQ Vel hosts a neutron star companion
• The near-infrared companion to HD94660 (=KQ Vel)