Haswell, Carole A.; Patterson, Joseph; Thorstensen, John R.; Hellier, Coel and Skillman, David R.
|DOI (Digital Object Identifier) Link:||http://dx.doi.org/10.1086/303630|
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We present 1 resolution fast ultraviolet spectroscopy of YY Dra, coordinated U, B, V, R, and I photometry, and Hα spectroscopy. The UV continuum is strongly pulsed: we found 16% semiamplitude pulses with period 264.7(1) s; there was no evidence for power at twice this period. The UBV pulses are in phase with the UV continuum pulsation. A color temperature of 105 K was found for the pulse spectrum, with a corresponding area 0.5% of the white dwarf surface. We refine the white dwarf spin period, obtaining Pspin = 529.31 ± 0.02 s. Optical pulses at 273(1) s were also detected; we attribute these to reprocessing in structures fixed in the orbital frame. Variations in the C iv line profile are apparent when the data are folded on Pspin. Faint, broad line wings extending to ±3000 km s−1 appear simultaneously with the continuum pulsation maxima. This implies that accretion was occurring onto both magnetic poles. Consequent constraints on the accretion geometry and white dwarf mass are derived, and a minimum white dwarf mass of 0.62 M is obtained. A color temperature T 30,000 K is derived for the unpulsed emission.
|Item Type:||Journal Article|
|Keywords:||stars : individual (YY Draconis) È stars : oscillations È ultraviolet : stars È white dwarfs|
|Academic Unit/Department:||Science > Physical Sciences
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)|
|Depositing User:||Astrid Peterkin|
|Date Deposited:||25 Jul 2008 11:25|
|Last Modified:||14 Jan 2016 17:02|
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