English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

OH 231.8+4.2, a bipolar outflow around a Mira-type variable star, displays aunique molecular richness amongst circumstellar envelopes (CSEs) around O-richAGB and post-AGB stars. We report line observations of the HCO+ and H13CO+molecular ions and the first detection of SO+, N2H+, and (tentatively) H3O+ inthis source. SO+ and H3O+ have not been detected before in CSEs around evolvedstars. These data have been obtained as part of a full mm-wave and far-IRspectral line survey carried out with the IRAM 30 m radio telescope and withHerschel/HIFI. Except for H3O+, all the molecular ions detected in this workdisplay emission lines with broad profiles (FWHM 50-90 km/s), which indicatesthat these ions are abundant in the fast bipolar outflow of OH 231.8. Thenarrow profile (FWHM 14 km/s) and high critical densities (>1e6cm-3 ) of theH3O+ transitions observed are consistent with this ion arising from denser,inner (and presumably warmer) layers of the fossil remnant of the slow AGB CSEat the core of the nebula. From rotational diagram analysis, we deduceexcitation temperatures of Tex 10-20 K for all ions except for H3O+, which ismost consistent with Tex 100 K. Although uncertain, the higher excitationtemperature suspected for H3O+ is similar to that recently found for H2O and afew other molecules, which selectively trace a previously unidentified, warmnebular component.The column densities of the molecular ions reported here arein the range Ntot [1-8]x1e13 cm-2, leading to beam-averaged fractionalabundances relative to H2 of X(HCO+) 1e-8, X(H13CO+) 2e-9, X(SO+) 4e-9, X(N2H+)2e-9, and X(H3O+) 7e-9 cm-2. We have performed chemical kinetics models toinvestigate the formation of these ions in OH 231.8 as the result of standardgas phase reactions initiated by cosmic-ray and UV-photon ionization.(abridged).

Molecular ions in the O-rich evolved star OH231.8+4.2: HCO$^+$,H$^{13}$CO$^+$ and first detection of SO$^+$, N$_2$H$^+$, and H$_3$O$^+$