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    Astrometry With The Hubble Space Telescope: Trigonometric Parallaxes Of Planetary Nebula Nuclei NGC 6853, NGC 7293, Abell 31, And Deht 5

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    Date
    2009-12
    Author
    Benedict, G. Fritz
    McArthur, Barbara E.
    Napiwotzki, Ralph
    Harrison, Thomas E.
    Harris, Hugh C.
    Nelan, Edmund
    Bond, Howard E.
    Patterson, Richard J.
    Ciardullo, Robin
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    Abstract
    We present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix), Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi) parallaxes with astrometric data from Fine Guidance Sensors FGS 1r and FGS 3, white-light interferometers on the Hubble Space Telescope. Proper motions, spectral classifications and VJHKT(2)M and DDO51 photometry of the stars comprising the astrometric reference frames provide spectrophotometric estimates of reference star absolute parallaxes. Introducing these into our model as observations with error, we determine absolute parallaxes for each PNN. Weighted averaging with previous independent parallax measurements yields an average parallax precision, sigma(pi)/pi = 5%. Derived distances are: d(NGC6853) = 405(-25)(+28) pc, d(NGC7293) = 216(-12)(+14) pc, d(Abell 31) = 621(-70)(+91) pc, and d(DeHt 5) = 345(-17)(+19) pc. These PNNi distances are all smaller than previously derived from spectroscopic analyses of the central stars. To obtain absolute magnitudes from these distances requires estimates of interstellar extinction. We average extinction measurements culled from the literature, from reddening based on PNNi intrinsic colors derived from model SEDs, and an assumption that each PNN experiences the same rate of extinction as a function of distance as do the reference stars nearest (in angular separation) to each central star. We also apply Lutz-Kelker bias corrections. The absolute magnitudes and effective temperatures permit estimates of PNNi radii through both the Stefan-Boltzmann relation and Eddington fluxes. Comparing absolute magnitudes with post-AGB models provides mass estimates. Masses cluster around 0.57 M-circle dot, close to the peak of the white dwarf mass distribution. Adding a few more PNNi with well-determined distances and masses, we compare all the PNNi with cooler white dwarfs of similar mass, and confirm, as expected, that PNNi have larger radii than white dwarfs that have reached their final cooling tracks.
    Department
    Astronomy
    Subject
    astrometry
    planetary nebulae: general
    stars: distances
    stars:
    fundamental parameters
    white dwarfs
    fine guidance sensor
    da white-dwarfs
    balmer line problem
    central
    stars
    interferometric astrometry
    old planetaries
    cataclysmic
    variables
    proxima centauri
    sirius-b
    mass
    astronomy & astrophysics
    URI
    http://hdl.handle.net/2152/34327
    xmlui.dri2xhtml.METS-1.0.item-citation
    Benedict, G. Fritz, Barbara E. McArthur, Ralf Napiwotzki, Thomas E. Harrison, Hugh C. Harris, Edmund Nelan, Howard E. Bond, Richard J. Patterson, and Robin Ciardullo. >Astrometry with the Hubble Space Telescope: Trigonometric Parallaxes of Planetary Nebula Nuclei NGC 6853, NGC 7293, Abell 31, and DeHt 5.> The Astronomical Journal Vol, 138, No. 6 (Dec., 2009): 1969.
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    • CONTACT US
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    © The University of Texas at Austin