Discovery of time variation of the intensity of molecular lines in IRC+10216 in the submillimeter and far-infrared domains
Journal article, 2014
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 lines of asymptotic giant branch stars can no longer be considered as safe intensity calibrators.
astrochemistry
stars: carbon
stars: AGB and post-AGB
10216)
stars: individual (IRC
Author
J. Cernicharo
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
D. Teyssier
European Space Astronomy Centre (ESAC)
G. Quintana-Lacaci
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
F. Daniel
Grenoble Alpes University
Centre national de la recherche scientifique (CNRS)
M. Agundez
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
L. Velilla-Prieto
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
L. Decin
KU Leuven
M. Guelin
Institut de Radioastronomie Millimétrique (IRAM)
P. Encrenaz
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
P. Garcia-Lario
European Space Astronomy Centre (ESAC)
Elvire De Beck
Chalmers, Earth and Space Sciences, Onsala Space Observatory
M. J. Barlow
University College London (UCL)
M. A. T. Groenewegen
Royal Observatory of Belgium
D. A. Neufeld
Johns Hopkins University
J. C. Pearson
Jet Propulsion Laboratory, California Institute of Technology
Astrophysical Journal Letters
2041-8205 (ISSN) 2041-8213 (eISSN)
Vol. 796 1 L21Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1088/2041-8205/796/1/l21