73 research outputs found
Discovery of a magnetic field in the B pulsating system HD 1976
The presence of a magnetic field can have a strong impact on the evolution of
a binary star. However, only a dozen of magnetic OB binaries are known as of
today and available to study this effect, including very few magnetic pulsating
spectroscopic OB binaries. We aim at checking for the presence of a magnetic
field in the B5IV hierarchical triple system HD 1976 with spectropolarimetric
data obtained with Narval at the Bernard Lyot Telescope (TBL). We use orbital
parameters of HD 1976 available in the literature to disentangle the Narval
intensity spectra. We compute Stokes V profiles with the Least Square
Deconvolution (LSD) technique to search for magnetic signatures. We then derive
an estimate of the longitudinal magnetic field strength for each observation
and for various line lists. Our disentangling of the intensity spectra shows
that HD 1976 is a double-lined spectroscopic (SB2) binary, with the lines of
the secondary component about twice broader than the ones of the primary
component. We do not identify the third component. Moreover, we find that clear
magnetic signatures are present in the spectropolarimetric measurements of HD
1976 and seem to be associated with the primary component. We conclude that HD
1976 is a magnetic slowly-pulsating double-lined spectroscopic binary star,
with an undetected third component. It is the second such example known (with
HD 25558).Comment: Accepted in A&A Letter to the Editor, 4 pages, 2 figures, 2 table
The Incidence of Magnetic Fields in Massive Stars: An Overview of the MiMeS Survey Component
With only a handful of known magnetic massive stars, there is a troubling
deficit in the scope of our knowledge of the influence of magnetic fields on
stellar evolution, and almost no empirical basis for understanding how fields
modify mass loss and rotation in massive stars. Most remarkably, there is still
no solid consensus regarding the origin physics of these fields - whether they
are fossil remnants, or produced by contemporaneous dynamos, or some
combination of these mechanisms. This article will present an overview of the
Survey Component of the MiMeS Large Programs, the primary goal of which is to
search for Zeeman signatures in the circular polarimetry of massive stars
(stars with spectral types B3 and hotter) that were previously unknown to host
any magnetic field. To date, the MiMeS collaboration has collected more than
550 high-resolution spectropolarimetric observations with ESPaDOnS and Narval
of nearly 170 different stars, from which we have discovered 14 new magnetic
stars.Comment: 7 pages (+1 for questions), 3 figures, to appear in proceedings of
Stellar polarimetry: From birth to deat
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&
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