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 (15)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• Confirmation of circumstellar phosphine
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• An independent distance estimate to CW Leo
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• On the physical structure of IRC+10216. Ground-based and Herschel observations of CO and CCH
• Silicon in the dust formation zone of IRC +10216 as observed with PACS and SPIRE on board Herschel
• Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines
• Spectroscopic parameters for silacyclopropynylidene, SiC${}_2$, from extensive astronomical observations toward CW Leo (IRC +10216) with the Herschel satellite
• Herschel/HIFI observation of highly excited rotational lines of HNC toward IRC +10 216

Cited by in corpus (36)

• 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
• Interstellar nitrile anions: Detection of C3N- and C5N- in TMC-1
• An observational study of dust nucleation in Mira ($o$ Ceti): I. Variable features of AlO and other Al-bearing species
• The Abundance of SiC2 in Carbon Star Envelopes: Evidence that SiC2 is a gas-phase precursor of SiC dust
• 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
• A 1.3 cm line survey toward IRC +10216
• New N-bearing species towards OH231.8+4.2: HNCO, HNCS, HC${}_3$N and NO
• 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
• Through the magnifying glass: ALMA acute viewing of the intricate nebular architecture of OH231.8+4.2
• A lambda 3mm and 1mm line survey toward the yellow hypergiant IRC +10420
• Discovery of two metallic cyanoacetylides in IRC+10216: HMgCCCN and NaCCCN
• The abundance of 28Si32S, 29Si32S, 28Si34S, and 30Si32S in the inner layers of the envelope of IRC+10216
• 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
• Constraints on the H2O formation mechanism in the wind of carbon-rich AGB stars
• A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
• Widespread HCN maser emission in carbon-rich evolved stars
• Extended Dust Emission from Nearby Evolved Stars
• Molecular line study of the S-type AGB star W Aquilae. ALMA observations of CS, SiS, SiO and HCN
• 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
• The maser emitting structure and time variability of the SiS lines J=14-13 and 15-14 in IRC+10216
• 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
• ALMA monitoring of mm line variation in IRC+10216: I. Overview of millimeter variability
• Warm CO in evolved stars from the THROES catalogue. II. Herschel/PACS spectroscopy of C-rich envelopes
• Detection of infrared fluorescence of carbon dioxide in R Leonis with SOFIA/EXES
• Discovery of a brown dwarf with quasi-spherical mass-loss
• IRC+10216 mass loss properties through the study of $\lambda$3mm emission: Large spatial scale distribution of SiO, SiS, and CS
• New submillimetre HCN lasers in carbon-rich evolved stars