364 research outputs found
The "Binarity and Magnetic Interactions in various classes of Stars" (BinaMIcS) project
The "Binarity and Magnetic Interactions in various classes of stars"
(BinaMIcS) project is based on two large programs of spectropolarimetric
observations with ESPaDOnS at CFHT and Narval at TBL. Three samples of
spectroscopic binaries with two spectra (SB2) are observed: known cool magnetic
binaries, the few known hot magnetic binaries, and a survey sample of hot
binaries to search for additional hot magnetic binaries. The goal of BinaMIcS
is to understand the complex interplay between stellar magnetism and binarity.
To this aim, we will characterise and model the magnetic fields, magnetospheric
structure and coupling of both components of hot and cool close binary systems
over a significant range of evolutionary stages, to confront current theories
and trigger new ones. First results already provided interesting clues, e.g.
about the origin of magnetism in hot stars.Comment: 4 pages, 2 figures, proceedings of the SF2A conferenc
Magnetic field topology of the unique chemically peculiar star CU Virginis
The late-B magnetic chemically peculiar star CU Vir is one of the fastest
rotators among the intermediate-mass stars with strong fossil magnetic fields.
It shows a prominent rotational modulation of the spectral energy distribution
and absorption line profiles due to chemical spots and exhibits a unique
strongly beamed variable radio emission. Little is known about the magnetic
field topology of CU Vir. In this study we aim to derive, for the first time,
detailed maps of the magnetic field distribution over the surface of this star.
We use high-resolution spectropolarimetric observations covering the entire
rotational period. These data are interpreted using a multi-line technique of
least-squares deconvolution (LSD) and a new Zeeman Doppler imaging code based
on detailed polarised radiative transfer modelling of the Stokes I and V LSD
profiles. This new magnetic inversion approach relies on the spectrum synthesis
calculations over the full wavelength range covered by observations and does
not assume that the LSD profiles behave as a single spectral line with mean
parameters. We present magnetic and chemical abundance maps derived from the Si
and Fe lines. Mean polarisation profiles of both elements reveal a significant
departure of the magnetic field topology of CU Vir from the commonly assumed
axisymmetric dipolar configuration. The field of CU Vir is dipolar-like, but
clearly non-axisymmetric, showing a large difference of the field strength
between the regions of opposite polarity. The main relative abundance depletion
features in both Si and Fe maps coincide with the weak-field region in the
magnetic map. Detailed information on the distorted dipolar magnetic field
topology of CU Vir provided by our study is essential for understanding
chemical spot formation, radio emission, and rotational period variation of
this star.Comment: 14 pages, 14 figures; accepted for publication in A&
HD66051: the first eclipsing binary hosting an early-type magnetic star
Early-type magnetic stars are rarely found in close binary systems. No such
objects were known in eclipsing binaries prior to this study. Here we
investigated the eclipsing, spectroscopic double-lined binary HD66051, which
exhibits out-of-eclipse photometric variations suggestive of surface brightness
inhomogeneities typical of early-type magnetic stars. Using a new set of
high-resolution spectropolarimetric observations, we discovered a weak magnetic
field on the primary and found intrinsic, element-dependent variability in its
spectral lines. The magnetic field structure of the primary is dominated by a
nearly axisymmetric dipolar component with a polar field strength G and an inclination with respect to the rotation axis of
. A weaker quadrupolar component is also likely to be
present. We combined the radial velocity measurements derived from our spectra
with archival optical photometry to determine fundamental masses (3.16 and 1.75
) and radii (2.78 and 1.39 ) with a 1-3% precision. We also
obtained a refined estimate of the effective temperatures (13000 and 9000 K)
and studied chemical abundances for both components with the help of
disentangled spectra. We demonstrate that the primary component of HD66051 is a
typical late-B magnetic chemically peculiar star with a non-uniform surface
chemical abundance distribution. It is not an HgMn-type star as suggested by
recent studies. The secondary is a metallic-line star showing neither a strong,
global magnetic field nor intrinsic spectral variability. Fundamental
parameters provided by our work for this interesting system open unique
possibilities for probing interior structure, studying atomic diffusion, and
constraining binary star evolution.Comment: 14 pages, 15 figures; accepted for publication in MNRA
Roadmap on the theoretical work of BinaMIcS
We review the different theoretical challenges concerning magnetism in
interacting binary or multiple stars that will be studied in the BinaMIcS
(Binarity and Magnetic Interactions in various classes of Stars) project during
the corresponding spectropolarimetric Large Programs at CFHT and TBL. We
describe how completely new and innovative topics will be studied with BinaMIcS
such as the complex interactions between tidal flows and stellar magnetic
fields, the MHD star-star interactions, and the role of stellar magnetism in
stellar formation and vice versa. This will strongly modify our vision of the
evolution of interacting binary and multiple stars.Comment: 2 pages, proceeding of IAUS 302 Magnetic fields throughout stellar
evolution, correct list of author
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