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RISS 인기검색어
- 검색키워드
- 저자 : Antonyuk, K. (검색결과 2 건)
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A STUDY OF THE PHOTOMETRIC VARIABILITY OF THE PECULIAR MAGNETIC WHITE DWARF WD 1953-011
Valyavin, G.,Antonyuk, K.,Plachinda, S.,Clark, D. M.,Wade, G. A.,Machado, Lester Fox,Alvarez, M.,Lopez, J. M.,Hiriart, D.,Han, Inwoo,Jeon, Young-Beom,Bagnulo, S.,Zharikov, S. V.,Zurita, C.,Mujica, R. IOP Publishing 2011 The Astrophysical journal Vol.734 No.1
<P>We present and interpret simultaneous new photometric and spectroscopic observations of the peculiar magnetic white dwarf WD 1953-011. The flux in the V-band filter and intensity of the Balmer spectral lines demonstrate variability with the rotation period of about 1.45 days. According to previous studies, this variability can be explained by the presence of a dark spot having a magnetic nature, analogous to a sunspot. Motivated by this idea, we examine possible physical relationships between the suggested dark spot and the strong-field magnetic structure (magnetic 'spot' or 'tube') recently identified on the surface of this star. Comparing the rotationally modulated flux with the variable spectral observables related to the magnetic 'spot,' we establish their correlation and therefore their physical relationship. Modeling the variable photometric flux assuming that it is associated with temperature variations in the stellar photosphere, we argue that the strong-field area and dark, low-temperature spot are comparable in size and located at the same latitudes, essentially overlapping each other with a possible slight longitudinal shift. In this paper, we also present a new, improved value of the star's rotational period and constrain the characteristics of the thermal inhomogeneity over the degenerate's surface.</P>
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Suppression of cooling by strong magnetic fields in white dwarf stars
Valyavin, G.,Shulyak, D.,Wade, G. A.,Antonyuk, K.,Zharikov, S. V.,Galazutdinov, G. A.,Plachinda, S.,Bagnulo, S.,Machado, L. Fox,Alvarez, M.,Clark, D. M.,Lopez, J. M.,Hiriart, D.,Han, Inwoo,Jeon, Young Nature Publishing Group, a division of Macmillan P 2014 Nature Vol.515 No.7525
Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.
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