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 asymptotic giant branch (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.

The population of planetary nebulae near the Galactic Centre: chemical abundances

“…However, for all but one object (JaSt 23) the velocity data are not available in the literature and, since the inner disc can extend into the inner kpc of the Galaxy (see a revision by Bland-Hawthorn & Gerhard 2016), we cannot rule out inner disc PNe contaminants in our sample. In the case of JaSt 23, the OH maser spectrum shows a single peak at VLSR = +115.2 km s −1 (Uscanga et al 2012), which is compatible with that expected for GBPNe. • of the GC.…”

Unusual Shock-Excited Oh Maser Emission in a Young Planetary Nebula

“…Uscanga et al (2012) find the sizes and optical visibilities of the maser-associated PNe suggest a range of ages, but it is possible that the subgroup of PNe showing both OH and H 2 O are among the youngest PNe known (Gómez et al 2015). Our observations confirm IRAS 16333−4807 as a member of this rare group of potentially young PNe.…”

“…Compared to the copious OH masers in the AGB phase, the prevalence of OH masers decays significantly in subsequent phases, and they are rarely found in PNe. So far, only six PNe have been confirmed to harbor OH masers (OHmaser-emiting PNe, hereafter referred to as OHPN/OHPNe; Zijlstra et al 1989;Uscanga et al 2012). They all show maser emission with strong asymmetry, i.e., preferentially blueshifted emission with respect to the stellar velocity (Uscanga et al 2012).…”

“…So far, only six PNe have been confirmed to harbor OH masers (OHmaser-emiting PNe, hereafter referred to as OHPN/OHPNe; Zijlstra et al 1989;Uscanga et al 2012). They all show maser emission with strong asymmetry, i.e., preferentially blueshifted emission with respect to the stellar velocity (Uscanga et al 2012). One of them, K 3−35, shows OH maser emission at all four ground-state transitions (1612, 1665, 1667, 1720 MHz; Gómez et al 2009), as well as excited-state masers at 6035 MHz (Desmurs et al 2010).…”

A survey for hydroxyl in the THOR pilot region around W43

“…Another exceedingly rare class of objects associated with evolved stars are OHPNe (Uscanga et al 2012). These objects show radio continuum emission associated with a PN, but also show OH maser emission.…”