Browsing by Author "Monteiro, H"

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    Proper motion and kinematics of the ansae in NGC 7009
    (2004) Fernández, R; Monteiro, H; Schwarz, HE
    We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high-dispersion echelle spectra and archive narrowband Hubble Space Telescope images. Assuming that the ansae are moving at equal and opposite velocities from the central star, we obtain a system radial velocity of -53 +/- 2 km s(-1), the eastern ansa approaching and the western ansa receding at v(r) = 5.3 +/- 1 km s(-1) with respect to this value. The PM of the eastern ansa is 28 +/- 8 mas yr(-1), which, with our weighted distance to NGC 7009 of 0.86 +/- 0.34 kpc, gives V-exp = 114 +/- 32 km s-(1). The electron temperature and density in both ansae were determined to be T-e similar to 9000 +/- 400 K and n(e) similar to 2300 +/- 400 cm(-3). The dynamic age of the ansae is similar to910 +/- 260 yr, and the implied PM of the central star is mu(CS) = 1 +/- 0.5 mas yr(-1). This is in qualitative but not quantitative agreement with previous work.