Mon. Not. R. Astron. Soc., 372, 1081-1092 (2006/November-1)
Two new evolved bipolar planetary nebulae in the solar neighbourhood.
FREW D.J., PARKER Q.A. and RUSSEIL D.
Abstract (from CDS):
We present AAO/UKST Hα+[N ii] narrow-band imagery and low- and medium-resolution optical spectroscopy of RCW24 and RCW69. These nebulae were previously classified as HII regions, but we now show them to be two of the largest and nearest bipolar Type I PNe yet discovered. Distances were estimated using extinction-distance and kinematic methods, and via a new Hα surface brightness-radius relation. The adopted distances are 1.0 ±0.3kpc for RCW24 and 1.3±0.2kpc for RCW69. Both objects have enhanced nitrogen abundances, with logN/O≃+0.44 for RCW24, and logN/O=+0.33 for RCW 69. Systemic velocities and|z| distances are VLSR= +5 km/s and|z| ∼ 23pc for RCW 24, and VLSR= -33 km/s and only|z| ∼ 7pc for RCW 69. Both PNe originated from massive progenitors (>2.0-2.5M☉), as deduced from their chemical abundances, large ionized masses, small|z| distances, low peculiar velocities and relatively hot central stars. These two objects form an important addition to the small sample of evolved bipolar PNe in the solar neighbourhood.