97 research outputs found
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
A MiMeS analysis of the magnetic field and circumstellar environment of the weak-wind O9 sub-giant star HD 57682
I will review our recent analysis of the magnetic properties of the O9IV star
HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the
Canada-France-Hawaii telescope within the context of the Magnetism in Massive
Stars (MiMeS) Large Program. I discuss our most recent determination of the
rotational period from longitudinal magnetic field measurements and Halpha
variability - the latter obtained from over a decade's worth of professional
and amateur spectroscopic observations. Lastly, I will report on our
investigation of the magnetic field geometry and the effects of the field on
the circumstellar environment.Comment: 2 pages, 2 figures, IAUS272 - Active OB Stars: Structure, Evolution,
Mass Loss and Critical Limit
An infrared diagnostic for magnetism in hot stars
Magnetospheric observational proxies are used for indirect detection of
magnetic fields in hot stars in the X-ray, UV, optical, and radio wavelength
ranges. To determine the viability of infrared (IR) hydrogen recombination
lines as a magnetic diagnostic for these stars, we have obtained low-resolution
(R~1200), near-IR spectra of the known magnetic B2V stars HR 5907 and HR 7355,
taken with the Ohio State Infrared Imager/Spectrometer (OSIRIS) attached to the
4.1m Southern Astrophysical Research (SOAR) Telescope. Both stars show definite
variable emission features in IR hydrogen lines of the Brackett series, with
similar properties as those found in optical spectra, including the derived
location of the detected magnetospheric plasma. These features also have the
added advantage of a lowered contribution of stellar flux at these wavelengths,
making circumstellar material more easily detectable. IR diagnostics will be
useful for the future study of magnetic hot stars, to detect and analyze
lower-density environments, and to detect magnetic candidates in areas obscured
from UV and optical observations, increasing the number of known magnetic stars
to determine basic formation properties and investigate the origin of their
magnetic fields.Comment: 4 pages, accepted for publication in A&
Of?p stars: a class of slowly rotating magnetic massive stars
Only 5 Of?p stars have been identified in the Galaxy. Of these, 3 have been
studied in detail, and within the past 5 years magnetic fields have been
detected in each of them. The observed magnetic and spectral characteristics
are indicative of organised magnetic fields, likely of fossil origin, confining
their supersonic stellar winds into dense, structured magnetospheres. The
systematic detection of magnetic fields in these stars strongly suggests that
the Of?p stars represent a general class of magnetic O-type stars.Comment: Proceedings of IAUS 272: Active OB star
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