PO and PN in the wind of the oxygen-rich AGB star IK Tau

Abstract

Phosphorus-bearing compounds have only been studied in the circumstellar environments (CSEs) of the asymptotic giant branch (AGB) star IRC +10216 and the protoplanetary nebula CRL 2688, both C-rich objects, and the O-rich red supergiant VY CMa. The current chemical models cannot reproduce the high abundances of PO and PN derived from observations of VY CMa. No observations have been reported of phosphorus in the CSEs of O-rich AGB stars. We aim to set observational constraints on the phosphorous chemistry in the CSEs of O-rich AGB stars, by focussing on the Mira-type variable star IK Tau. Using the IRAM 30m telescope and the Submillimeter Array (SMA), we observed four rotational transitions of PN (J=2-1,3-2,6-5,7-6) and four of PO (J=5/2-3/2,7/2-5/2,13/2-11/2,15/2-13/2). The IRAM 30m observations were dedicated line observations, while the SMA data come from an unbiased spectral survey in the frequency range 279-355 GHz. We present the first detections of PN and PO in an O-rich AGB star and estimate abundances X(PN/H2) of about 3x10^-7 and X(PO/H2) in the range 0.5-6.0x10^-7. This is several orders of magnitude higher than what is found for the C-rich AGB star IRC +10216. The diameter (<=0.7") of the PN and PO emission distributions measured in the interferometric data corresponds to a maximum radial extent of about 40 stellar radii. The abundances and the spatial occurrence of the molecules are in very good agreement with the results reported for VY CMa. We did not detect PS or PH3 in the survey. We suggest that PN and PO are the main carriers of phosphorus in the gas phase, with abundances possibly up to several 10^-7. The current chemical models cannot account for this, underlining the strong need for updated chemical models that include phosphorous compounds.

Accepted for publication in Astronomy & Astrophysics, 10 pages, 8 figures

References in corpus (5)

• Pure rotational spectra of TiO and TiO_2 in VY Canis Majoris
• A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
• The size, luminosity and motion of the extreme carbon star IRC+10216 (CW Leonis)
• Tentative detection of phosphine in IRC+10216
• An independent distance estimate to CW Leo

Cited by in corpus (36)

• Dust formation in the oxygen-rich AGB star IK Tau
• Confirmation of circumstellar phosphine
• ALMA and ROSINA detections of phosphorus-bearing molecules: the interstellar thread between star-forming regions and comets
• Chemical equilibrium in AGB atmospheres: Successes, failures, and prospects for small molecules, clusters, and condensates
• Phosphorus-bearing molecules in solar-type star forming regions: First PO detection
• First detections of the key prebiotic molecule PO in star-forming regions
• The millimeter IRAM-30m line survey toward IK Tau
• Tracing the phase transition of Al-bearing species from molecules to dust in AGB winds. Constraining the presence of gas-phase (Al2O3)n clusters
• ExoMol molecular line lists - XXIII: spectra of PO and PS
• Phosphorus-bearing molecules in the Galactic Center
• The ExoMol Atlas of Molecular Opacities
• The chemistry of phosphorus-bearing molecules under energetic phenomena
• ALMA spectral line and imaging survey of a low and a high mass-loss rate AGB star between 335 and 362 GHz
• Phosphorus-bearing molecules in massive dense cores
• The Astrophysical Multimessenger Observatory Network (AMON): Performance and Science Program
• The first steps of Interstellar Phosphorus Chemistry
• On the origin of phosphorus nitride in star-forming regions
• Origin of the PN molecule in star-forming regions: the enlarged sample
• Sulphur-bearing molecules in AGB stars I: The occurrence of hydrogen sulfide
• Circumstellar environment of the M-type AGB star R Dor. APEX spectral scan at $159.0-368.5$ GHz
• Search for aluminium monoxide in the winds of oxygen-rich AGB stars
• Chemical complexity of phosphorous bearing species in various regions of the Interstellar medium
• Exploring the innermost dust formation region of the oxygen-rich AGB star IK~Tau with VLT/SPHERE-ZIMPOL and VLTI/AMBER
• Circumstellar ammonia in oxygen-rich evolved stars
• Experimental study of the removal of excited state phosphorus atoms by H${}_2$O and H${}_2$: implications for the formation of PO in stellar winds
• Abundances and Depletions of Neutron-Capture Elements in the Interstellar Medium
• Rovibronic spectroscopy of PN from first principles
• Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes -- I. The case of hydrogen cyanide
• The surprisingly carbon-rich environment of the S-type star W Aql
• Chemistry in AGB stars: successes and challenges
• Multi-frequency high spectral resolution observations of HCN toward the circumstellar envelope of Y CVn
• New routes for PN destruction and formation in the ISM via neutral-neutral gas-phase reactions and an extended database for reactions involving phosphorus
• Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
• PACS and SPIRE range spectroscopy of cool, evolved stars
• Exploring circumstellar chemistry in X-ray emitting AGB stars
• Revisiting the formation of molecules and dust in core collapse supernovae