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2006 Whole Earth Telescope Observations of GD358: A New Look at the Prototype DBV | | J. L. Provencal
; M. H. Montgomery
; A. Kanaan
; H. L. Shipman
; D. Childers
; A. Baran
; S. O. Kepler
; M. Reed
; A. Zhou
; J. Eggen
; T. K. Watson
; D. E. Winget
; S. E. Thompson
; B. Riaz
; A. Nitta
; S. J. Kleinman
; R. Crowe
; J. Slivkoff
; P. Sherard
; N. Purves
; P. Binder
; R. Knight
; S. -L. Kim
; Wen-Ping Chen
; M. Yang
; H. C. Lin
; C. C. Lin
; C. W. Chen
; X. J. Jiang
; A. V. Sergeev
; D. Mkrtichian
; E. Janiashvili
; M. Andreev
; R. Janulis
; M. Siwak
; S. Zola
; D. Koziel
; G. Stachowski
; M. Paparo
; Zs. Bognar
; G. Handler
; D. Lorenz
; B. Steininger
; P. Beck
; T. Nagel
; D. Kusterer
; A. Hoffman
; E. Reiff
; R. Kowalski
; G. Vauclair
; S. Charpinet
; M. Chevreton
; J. E. Solheim
; E. Pakstiene
; L. Fraga
; J. Dalessio
; | | Date: |
5 Nov 2008 | | Abstract: | We report on the analysis of 436.1 hrs of nearly continuous high-speed
photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth
Telescope (WET) during the 2006 international observing run, designated XCOV25.
The Fourier transform (FT) of the light curve contains power between 1000 to
4000 microHz, with the dominant peak at 1234 microHz. We find 27 independent
frequencies distributed in 10 modes, as well as numerous combination
frequencies. Our discussion focuses on a new asteroseismological analysis of
GD358, incorporating the 2006 data set and drawing on 24 years of archival
observations. Our results reveal that, while the general frequency locations of
the identified modes are consistent throughout the years, the multiplet
structure is complex and cannot be interpreted simply as l=1 modes in the limit
of slow rotation. The high k multiplets exhibit significant variability in
structure, amplitude and frequency. Any identification of the m components for
the high k multiplets is highly suspect. The k=9 and 8 modes typically do show
triplet structure more consistent with theoretical expectations. The
frequencies and amplitudes exhibit some variability, but much less than the
high k modes. Analysis of the k=9 and 8 multiplet splittings from 1990 to 2008
reveal a long-term change in multiplet splittings coinciding with the 1996
"sforzando" event, where GD358 dramatically altered its pulsation
characteristics on a timescale of hours. We explore potential implications,
including the possible connections between convection and/or magnetic fields
and pulsations. We suggest future investigations, including theoretical
investigations of the relationship between magnetic fields, pulsation, growth
rates, and convection. | | Source: | arXiv, 0811.0768 | | Services: | Forum | Review | PDF | Favorites | |
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