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Post Info TOPIC: HD 37776
Blobrana


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RE: HD 37776
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Title: The extraordinary complex magnetic field of the helium-strong star HD 37776
Authors: Oleg Kochukhov, Andreas Lundin, Iosif Romanyuk, Dmitry Kudryavtsev

The early-type chemically peculiar stars often show strong magnetic fields on their surfaces. These magnetic topologies are organised on large scales and are believed to be close to an oblique dipole for most of the stars. In a striking exception to this general trend, the helium-strong star HD 37776 shows an extraordinary double-wave rotational modulation of the longitudinal magnetic field measurements, indicating a topologically complex and, possibly, record strong magnetic field. Here we present a new investigation of the magnetic field structure of HD 37776, using both simple geometrical interpretation of the longitudinal field curve and detailed modelling of the time-resolved circular polarisation line profiles with the help of magnetic Doppler imaging technique. We derive a model of the magnetic field structure of HD 37776, which reconciles for the first time all magnetic observations available for this star. We find that the local surface field strength does not exceed ~30 kG, while the overall field topology of HD 37776 is dominated by a non-axisymmetric component and represents by far the most complex magnetic field configuration found among early-type stars.

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Blobrana


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Posts: 131433
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Title: The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution
Authors: J. Krticka, Z. Mikulasek, J. Zverko, J. Ziznovsky

We simulate light curves of the helium strong chemically peculiar star HD 37776 assuming that the observed periodic light variations originate as a result of inhomogeneous horizontal distribution of chemical elements on the surface of a rotating star. We show that chemical peculiarity influences the monochromatic radiative flux, mainly due to bound-free processes. Using the model of the distribution of silicon and helium on HD 37776 surface, derived from spectroscopy, we calculate a photometric map of the surface and consequently the uvby light curves of this star. Basically, the predicted light curves agree in shape and amplitude with the observed ones. We conclude that the basic properties of variability of this helium strong chemically peculiar star can be understood in terms of the model of spots with peculiar chemical composition.

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