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Title: UNVEILING THE DUST NUCLEATION ZONE OF IRC+10216 WITH ALMA

We report the detection in IRC+10216 of lines of HNC J = 3 – 2 pertaining to nine excited vibrational states with energies up to ∼5300 K. The spectrum, observed with ALMA, also shows a surprising large number of narrow, unidentified lines that arise in the vicinity of the star. The HNC data are interpreted through a 1D-spherical non-local radiative transfer model, coupled to a chemical model that includes chemistry at thermochemical equilibrium for the innermost regions and reaction kinetics for the external envelope. Although unresolved by the current early ALMA data, the radius inferred for the emitting region is ∼0.''06 (i.e., ≅ 3 stellar radii), similar to the size of the dusty clumps reported by IR studies of the innermost region (r < 0.''3). The derived abundance of HNC relative to H{sub 2} is 10{sup –8} < χ(HNC) <10{sup –6}, and drops quickly where the gas density decreases and the gas chemistry is dominated by reaction kinetics. Merging HNC data with that of molecular species present throughout the inner envelope, such as vibrationally excited HCN, SiS, CS, or SiO, should allow us to characterize the physical and chemical conditions in the dust formation zone.
Authors:
; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Departamento de Astrofísica, Centro de Astrobiología, CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, E-28850 Madrid (Spain)
  2. Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406, Saint Martin dHères (France)
  3. Univ. Bordeaux, LAB, UMR 5804, F-33270, Floirac (France)
  4. NRAO, 520 Edgemont Road, Charlottesville, VA 22902 (United States)
  5. Université de Toulouse, UPS-OMP, IRAP, Toulouse (France)
Publication Date:
OSTI Identifier:
22364124
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COSMIC DUST; DETECTION; EQUILIBRIUM; HYDROCYANIC ACID; HYDROGEN; NUCLEATION; RADIANT HEAT TRANSFER; REACTION KINETICS; SILICON OXIDES; SPHERICAL CONFIGURATION; STARS; VIBRATIONAL STATES