An updated catalog of OH-maser-emitting planetary nebulae

Abstract

Aims. We studied the characteristics of planetary nebulae (PNe) that show both OH maser and radio continuum emission (hereafter OHPNe). These have been proposed to be very young PNe, and therefore, they could be key objects for understanding the formation and evolution of PNe. Methods. We consulted the literature searching for interferometric observations of radio continuum and OH masers toward evolved stars, including the information from several surveys. We also processed radio continuum and OH maser observations toward PNe in the Very Large Array data archive. The high positional accuracy provided by interferometric observations allow us to confirm or reject the association between OH maser and radio continuum emission. Results. We found a total of six PNe that present both OH maser and radio continuum emissions, as confirmed with radio interferometric observations. These are bona fide OHPNe. The confirmed OHPNe present a bipolar morphology in resolved images of their ionized emission at different wavelengths, suggesting that the OH maser emission in PNe is related to nonspherical mass-loss phenomena. The OH maser spectra in PNe present a clear asymmetry, tending to show blueshifted emission with respect to the systemic velocity. Their infrared colors suggest that most of these objects are very young PNe. OHPNe do not form a homogeneous group, and seem to represent a variety of different evolutionary stages. We suggest that OH masers pumped in the AGB phase may disappear during the post-AGB phase, but reappear once the source becomes a PN and its radio continuum emission is amplified by the OH molecules. Therefore, OH maser emission could last significantly longer than the previously assumed 1000 yr after the end of the AGB phase. This maser lifetime may be longer in PNe with more massive central stars, which ionize a larger amount of gas in the envelope.

16 pages, 5 figures, 4 tables. Accepted for publication by Astronomy & Astrophysics

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Cited by in corpus (14)

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• A Survey for Hydroxyl in the THOR Pilot Region around W43
• The first "water fountain" collimated outflow in a planetary nebula
• Accurate OH maser positions II. the Galactic Center region
• Polarization properties of OH emission in planetary nebulae
• Accurate OH Maser Positions From The SPLASH Survey III: The Final 96 Square Degrees
• A search for water maser emission toward obscured post-AGB star and planetary nebula candidates
• The population of planetary nebulae near the Galactic centre: chemical abundances
• CO line observations of OH/IR stars in the inner Galactic Bulge: Characteristics of stars at the tip of the AGB
• Searching for nascent planetary nebulae: OHPNe candidates in the SPLASH survey
• Detection of 4765 MHz OH Emission in a Pre-Planetary Nebula -- CRL 618