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Session 90 - Supernovae, Supernovae Remnants and Planetary Nebulae.
Oral session, Wednesday, January 17
Salon del Rey Central, Hilton
Jacoby amp; Fullton (1994, BAAS, 26, 1384; ApJS, in preparation) have searched nearly the entire Galactic globular cluster system for previously unknown Planetary Nebulae (PNe) using the on-band/off-band imaging technique at [O III] \lambda5007ÅWe present preliminary results for 3 newly discovered objects.
One PN associated was found in the globular cluster NGC 6441. Verification spectra indicate that nebular oxygen is severely depleted, with [O/H] \approx -1.3 dex (using ionization correction schemes) or [O/H] \approx -1.0 dex (using the CLOUDY photoionization model). NGC 6441 has [Fe/H] = -0.5 (Djorgovski 1993), so [O/Fe] = -0.8 to -0.5 dex if it belongs to the cluster. Ne/O is \approx 0.2, which is typical for PN. Nitrogen and sulfur lines are absent and HeII \lambda 4686 is very strong, suggesting that the central star has T_eff > 80,000 K. Nebular emission lines are redshifted relative to cluster stars by \approx 20 km/s. (The PNe in M15 and M22 are similarly blueshifted.) The PN still may be a cluster member despite the velocity shift if the nebular gas is distributed asymmetrically or if it has been impeded by the ISM relative to the cluster's motion.
(2) A well-resolved PN was discovered near Pal 6. This PN is located far (230^\prime\prime northeast) from the cluster center and consequently, may be a bulge planetary (at 2.8 degrees from the Galactic Center). The object was confirmed spectroscopically to be a PN with strong [NII] lines.
(3) An unusual object was discovered 68^\prime\prime west of Ter 2. It is evident in the \lambda 5007 image and absent or extremely weak in the continuum image. It is very faint in V, bright in R, and very bright in I (Armandroff, priv. comm.). A low signal-to-noise spectrum of the star from 5700--6800Å\ reveals no evidence of PN emission lines. The star is an IRAS source, having 12, 25 and 60 micron fluxes consistent with an OH/IR star. If the star does have emission at [O III], we may have caught it in the act of turning into a PN.
Program listing for Wednesday