Discovery of time variation of the intensity of molecular lines in IRC+10216 in the submillimeter and far-infrared domains
Artikel i vetenskaplig tidskrift, 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.


stars: AGB and post-AGB


stars: carbon

stars: individual (IRC


J. Cernicharo

CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)

D. Teyssier

European Space Astronomy Centre

G. Quintana-Lacaci

CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)

F. Daniel

Université Grenoble Alpes

CNRS Centre National de la Recherche Scientifique

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 Millimetrique (IRAM)

P. Encrenaz

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

P. Garcia-Lario

European Space Astronomy Centre

Elvire De Beck

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

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 L21


Astronomi, astrofysik och kosmologi