Discovery of Time Variation of the Intensity of Molecular Lines in IRC+10216 in The Submillimeter and Far Infrared Domains

Abstract

We report on the discovery of strong intensity variations in the high rotational lines of abundant molecular species towards the archetypical circumstellar envelope of IRC+10216. The observations have been carried out with the HIFI instrument on board \textit{Herschel}\thanks{\textit{Herschel} is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA} and with the IRAM\thanks{This work was based on observations carried out with the IRAM 30-meter telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain)} 30-m telescope. They cover several observing periods spreading over 3 years. The line intensity variations for molecules produced in the external layers of the envelope most probably 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 have to 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 sub-mm and FIR lines of AGB stars cannot anymore be considered as safe intensity calibrators.

References in corpus (4)

• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Confirmation of circumstellar phosphine
• A Detailed Analysis of the Dust Formation Zone of IRC+10216 Derived from Mid-IR Bands of C2H2 and HCN
• Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines

Cited by in corpus (24)

• Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of SiC bonds
• Molecular shells in IRC+10216: tracing the mass loss history
• The millimeter IRAM-30m line survey toward IK Tau
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• The magnesium paradigm in IRC+10216: Discovery of MgC${}_4$H${}^{+}$, MgC${}_3$N${}^{+}$, MgC${}_6$H${}^{+}$, and MgC${}_5$N${}^{+}$
• Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Dor: Non-LTE abundance analysis of CO, SiO, and HCN
• New N-bearing species towards OH231.8+4.2: HNCO, HNCS, HC${}_3$N and NO
• A 1.3 cm line survey toward IRC +10216
• Discovery of the first Ca-bearing molecule in space: CaNC
• ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars: Motivation, sample, calibration, and initial results
• Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN
• Systematic characterisation of the Herschel SPIRE Fourier Transform Spectrometer
• Investigating Anomalous Photochemistry in the Inner Wind of IRC+10216 Through Interferometric Observations of HC${}_3$N
• A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
• The surprisingly carbon-rich environment of the S-type star W Aql
• Monitor variability of millimeter lines in IRC +10216
• SiS in the circumstellar envelope of IRC +10126: maser and quasi-thermal emission
• Molecules in the carbon-rich protoplanetary nebula CRL 2688
• The Arizona Molecular ISM Survey with the SMT: Survey Overview and Public Data Release
• Charting Circumstellar Chemistry of Carbon-rich AGB Stars: I. ALMA 3 mm spectral surveys
• Warm CO in evolved stars from the THROES catalogue. II. Herschel/PACS spectroscopy of C-rich envelopes
• Discovery of a brown dwarf with quasi-spherical mass-loss
• Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES
• New submillimetre HCN lasers in carbon-rich evolved stars