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Title: DISCOVERY OF TIME VARIATION OF THE INTENSITY OF MOLECULAR LINES IN IRC+10216 IN THE SUBMILLIMETER AND FAR-INFRARED DOMAINS

We report on the discovery of strong intensity variations in the high rotational lines of abundant molecular species toward the archetypical circumstellar envelope of IRC+10216. The observations have been carried out with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument on board Herschel and with the IRAM30 m telescope. They cover several observing periods spreading over three years. The line intensity variations for molecules produced in the external layers of the envelope most likely result from time variations in the infrared pumping rates. We analyze the main implications this discovery has on the interpretation of molecular line emission in the envelopes of Mira-type stars. Radiative transfer calculations must take into account both the time variability of infrared pumping and the possible variation of the dust and gas temperatures with stellar phase in order to reproduce the observation of molecular lines at different epochs. The effect of gas temperature variations with stellar phase could be particularly important for lines produced in the innermost regions of the envelope. Each layer of the circumstellar envelope sees the stellar light radiation with a different lag time (phase). Our results show that this effect must be included in the models. The submillimeter and far infrared linesmore » of asymptotic giant branch stars can no longer be considered as safe intensity calibrators.« less
Authors:
; ; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11]
  1. Group of Molecular Astrophysics, ICMM, CSIC, C/Sor Juana Inés de La Cruz N3, E-28049 Madrid (Spain)
  2. ESA, ESAC, P.O. Box 78, Villanueva de la Cañada, E-28691 Madrid (Spain)
  3. Univ. Grenoble Alpes, IPAG, F-38000 Grenoble (France)
  4. Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)
  5. Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, F-38406 St-Martin d'Hères (France)
  6. LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris (France)
  7. Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE 439 92 Onsala (Sweden)
  8. Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)
  9. Koninklijke Sterrenwacht van België, Ringlaan 3, B-1180 Brussels (Belgium)
  10. Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)
  11. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
Publication Date:
OSTI Identifier:
22364904
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 796; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMPTOTIC SOLUTIONS; CARBON; COSMIC DUST; EMISSION SPECTRA; FAR INFRARED RADIATION; LAYERS; MOLECULES; RADIANT HEAT TRANSFER; STARS; TELESCOPES; TIME DEPENDENCE; VISIBLE RADIATION