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The nebula Mz 3 has arguably the most complex bipolar morphology, consisting of three nested pairs of bipolar lobes and an equatorial ellipse. Its three pairs of bipolar lobes share the same axis of symmetry, but have very different opening angles and morphologies: the innermost pair of bipolar lobes shows closed lobe morphology, while the other two have open lobes with cylindrical and conical shapes, respectively. We have carried out high-dispersion spectroscopic observations of Mz 3, and detected distinct kinematic properties among the different morphological components. The expansion characteristics of the two outer pairs of lobes suggest that they originated in an explosive event, whereas the innermost pair of lobes resulted from the interaction of a fast wind with the surrounding material. The equatorial ellipse is associated with a fast equatorial outflow which is unique among bipolar nebulae. The dynamical ages of the different structures in Mz 3 suggest episodic bipolar ejections, and the distinct morphologies and kinematics among these different structures reveal fundamental changes in the system between these episodic ejections., Comment: To be published in the October issue of The Astronomical Journal. 16 pages, 10 figures. For full resolution figures, send requests to the Author mar@iaa.es

We report on a water maser survey towards a sample of 27 planetary nebulae (PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well as the Very Large Array (VLA). Two detections have been obtained: the already known water maser emission in K 3-35, and a new cluster of masers in IRAS 17347-3139. This low rate of detections is compatible with the short life-time of water molecules in PNe (~100 yr). The water maser cluster at IRAS 17347-3139 are distributed on a ellipse of size ~ 0.2" x 0.1", spatially associated with compact 1.3 cm continuum emission (simultaneously observed with the VLA). From archive VLA continuum data at 4.9, 8.4, and 14.9 GHz, a spectral index alpha = 0.76 +- 0.03 is derived for this radio source, which is consistent with either a partially optically thick ionized region or with an ionized wind. However, the latter scenario can be ruled out on mass-loss considerations, thus indicating that this source is probably a young PN. The spatial distribution and the radial velocities of the water masers are suggestive of a rotating and expanding maser ring, tracing the innermost regions of a torus formed at the end of the AGB phase. Given that the 1.3 cm continuum emission peak is located near one of the tips of the major axis of the ellipse of masers, we speculate on a possible binary nature of IRAS 17347-3139, where the radio continuum emission could belong to one of the components and the water masers would be associated with a companion., Comment: Accepted by The Astrophysical Journal. 25 pages, 6 figures

We present narrow-band images and long-slit echelle spectra of the planetary nebula (PN) NGC 6778. The data show this PN as bipolar, with a very prominent low-excitation equatorial toroid, high-excitation lobes and two pairs of collimated outflows. Morphologically, the pairs of outflows are different from each other; one is linear and oriented along the bipolar axis, the other presents an S-shape with changing orientations. Besides the different morphology, both pairs of collimated outflows present radial velocities increasing with distance from the central star and share a common origin in bright knots at the tips of the shell., Comment: 4 pages, 2 figures; to appear in Asymmetric Planetary Nebulae III, eds. M. Meixner, J. Kastner, N.Soker and B. Balick (ASP Conf. Ser.)

We present a spatio-kinematical study of the planetary nebula (PN) IC 4634 which has experienced several episodes of point-symmetric ejections oriented at different directions. The nebula displays two S-shaped low-ionization arcs that are probably related to two relatively recent point-symmetric ejections, the outer S-shaped arc representing a beautiful example of a bow-shock resolved in a PN. We report here the discovery of an arc-like string of knots at larger distances from IC 4634 central star that represents a much earlier point-symmetric ejection., Comment: 2 pages, 1 figure; to appear in "Asymmetrical Planetary Nebulae III" editors M. Meixner, J. Kastner, N. Soker, & B. Balick (ASP Conf. Series)

High resolution images at different wavelengths show the common presence of structures and microstructures in planetary nebulae (PNe), which are not well incorporated to the existing models for the formation of these objects. We summarize how studies of the internal kinematics, combined with the information provided by high resolution images, may help to establish the nature and possible origin of the observed structures as well as to provide information about the physical processes involved in the formation and evolution of PNe., Comment: 7 pages, 4 figures; to appear in "Asymmetrical Planetary Nebulae III" editors M. Meixner, J. Kastner, N. Soker, & B. Balick (ASP Conf. Series)

We present high-dispersion echelle spectroscopic observations and a narrow-band [N II] image of the remarkable jet-like features of He 2-90. They are detected in the echelle spectra in the H-alpha and [N II] lines but not in other nebular lines. The [N II]/H-alpha ratio is uniformly high, ~1. The observed kinematics reveals bipolar collimated outflows in the jet-like features and shows that the southeast (northwest) component expands towards (away from) the observer at a remarkably constant line-of-sight velocity, 26.0+-0.5 km/s. The observed expansion velocity and the opening angle of the jet-like features are used to estimate an inclination angle of ~5 degrees with respect to the sky plane and a space expansion velocity of ~290 km/s. The spectrum of the bright central nebula reveals a profusion of Fe lines and extended wings of the H-alpha line, similar to those seen in symbiotic stars and some young planetary nebulae that are presumed to host a mass-exchanging binary system. If this is the case for He 2-90, the constant velocity and direction of the jets require a very stable dynamic system against precession and warping., Comment: 8 pages (emulate ApJ), 5 figure, 1 table

We present [N II] and H-alpha images and high resolution long-slit spectra of the planetary nebula IC 4846, which reveal, for the first time, its complex structure and the existence of collimated outflows. The object consists of a moderately elongated shell, two (and probably three) pairs of collimated bipolar outflows at different orientations, and an attached circular shell. One of the collimated pairs is constituted by two curved, extended filaments whose properties indicate a high velocity, bipolar precessing jet. A difference of \~10 km/s is found between the systemic velocity of the precessing jets and the centroid velocity of the nebula, as recently report for Hu 2-1. We propose that this difference is due to orbital motion of the ejection source in a binary central star. The orbital separation and period estimates for the binary star are less than or equal to 30 AU and 100 yr, respectively. These are similar to those previously estimated for Hu 2-1, linking the central stars of both planetary nebulae to interacting binaries. Extraordinary similarities also exist between IC 4846 and the bewildering planetary nebula NGC 6543, suggesting a similar formation history for both objects., Comment: 13 pages, 3 figures, to be published in MNRAS

We present narrow-band optical images, VLA-A 3.6 cm continuum and H92alpha emission line data and high resolution long-slit [N II] spectra of Hu 2-1. The formation of Hu 2-1 appears dominated by anisotropic mass ejection during the late AGB stage of its progenitor and by variable, ``precessing'' collimated bipolar outflows during the proto-PN and/or early PN phases. The data strongly support the existence of a binary central star at center of Hu 2-1: (1) the brightness distribution of the bipolar lobes and inner shell is point-symmetric, and the bipolar lobes show departures from axial symmetry; (2) the position of the central star is off-center; (3) mass ejection towards the equatorial plane is detected; (4) ``precessing'' collimated outflows are present. Besides all this circumstantial evidences, the analysis of the kinematics shows that the systemic velocity of the bipolar outflows does not coincide with the systemic velocity of the nebula. We propose that this velocity difference is a direct evidence of orbital motion of the ejection source in a binary system. Assuming a reasonable range of masses for the progenitor stars, the orbital velocity of ~10 km/s corresponds to a semi-major axis of 9-27 AU and to a period of 25-80 yr. The formation of Hu 2-1 is analyzed within current scenarios of PN formation with binary central stars., Comment: 18 pages, 9 figures, to be published in MNRAS

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