Non-local thermodynamic equilibrium line profiles, rotation, and magnetic fields in seven DA white dwarfs

Koester, D.; Herrero, A.
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Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 332, Sept. 15, 1988, p. 910-916.

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Non-LTE calculations of H-alpha line profiles are presented and applied to derive rotational velocities from high-resolution spectra of DA white dwarfs. This paper extends recent work by Pilachowski and Milkey (1984, 1987) to southern hemisphere objects and confirms their findings that all white dwarfs seem to be slow rotators. Of the seven objects in this study only one has v sin 1 = 30 + or - 20 km/s, only marginally different from 0. The remaining objects are all fitted by v sin 1 = 0, and upper limits of 20-40 km/s were obtained. Upper limits on magnetic fields of 25,000 G were determined for all objects from the absence of Zeeman splitting.