A high resolution line survey of IRC+10216 with Herschel. First results: Detection of warm silicon dicarbide SiC2

Abstract

We present the first results of a high-spectral-resolution survey of the carbon-rich evolved star IRC+10216 that was carried out with the HIFI spectrometer onboard Herschel. This survey covers all HIFI bands, with a spectral range from 488 to 1901GHz. In this letter we focus on the band-1b spectrum, in a spectral range 554.5-636.5GHz, where we identified 130 spectral features with intensities above 0.03 K and a signal-to-noise ratio >5. Detected lines arise from HCN, SiO, SiS, CS, CO, metal-bearing species and, surprisingly, silicon dicarbide (SiC2). We identified 55 SiC2 transitions involving energy levels between 300 and 900 K. By analysing these rotational lines, we conclude that SiC2 is produced in the inner dust formation zone, with an abundance of ~2x10^-7 relative to molecular hydrogen. These SiC2 lines have been observed for the first time in space and have been used to derive an SiC2 rotational temperature of ~204 K and a source-averaged column density of ~6.4x10^15 cm^-2. Furthermore, the high quality of the HIFI data set was used to improve the spectroscopic rotational constants of SiC2.

A&A HIFI Special Issue, 2010

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• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Herschel-SPIRE instrument and its in-flight performance
• Detection of C5N- and vibrationally excited C6H in IRC +10216
• Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216
• A Detailed Analysis of the Dust Formation Zone of IRC+10216 Derived from Mid-IR Bands of C2H2 and HCN
• A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
• Detection of anhydrous hydrochloric acid, HCl, in IRC+10216 with the Herschel SPIRE and PACS spectrometers
• Silicon in the dust formation zone of IRC +10216 as observed with PACS and SPIRE on board Herschel
• Herschel/HIFI observations of high-J CO transitions in the protoplanetary nebula CRL618

Cited by in corpus (50)

• Molecular abundances in the inner layers of IRC +10216
• Confirmation of circumstellar phosphine
• The inner wind of IRC+10216 revisited: New exotic chemistry and diagnostic for dust condensation in carbon stars
• Chemical equilibrium in AGB atmospheres: Successes, failures, and prospects for small molecules, clusters, and condensates
• Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of SiC bonds
• ALMA data suggest the presence of a spiral structure in the inner wind of CW Leo
• PO and PN in the wind of the oxygen-rich AGB star IK Tau
• Molecular shells in IRC+10216: tracing the mass loss history
• An Interferometric Spectral-line Survey of IRC+10216 in the 345 GHz Band
• Unveiling the dust nucleation zone of IRC+10216 with ALMA
• Discovery of Time Variation of the Intensity of Molecular Lines in IRC+10216 in The Submillimeter and Far Infrared Domains
• Si-bearing molecules towards IRC+10216: ALMA unveils the molecular envelope of CWLeo
• A HIFI view on circumstellar H2O in M-type AGB stars: radiative transfer, velocity profiles, and H2O line cooling
• The Abundance of SiC2 in Carbon Star Envelopes: Evidence that SiC2 is a gas-phase precursor of SiC dust
• A Search for Hydroxylamine (NH2OH) toward Select Astronomical Sources
• Water in IRC+10216: a genuine formation process by shock-induced chemistry in the inner wind
• HIFI detection of HF in the carbon star envelope IRC +10216
• On the physical structure of IRC+10216. Ground-based and Herschel observations of CO and CCH
• A 1.3 cm line survey toward IRC +10216
• Photodissociation and chemistry of N${}_2$ in the circumstellar envelope of carbon-rich AGB stars
• The complex dust formation zone of the AGB star IRC+10216 probed with CARMA 0.25 arcsec angular resolution molecular observations
• Molecular ions in the O-rich evolved star OH231.8+4.2: HCO${}^{+}$,H${}^{13}$CO${}^{+}$ and first detection of SO${}^{+}$, N${}_2$H${}^{+}$, and H${}_3$O${}^{+}$
• Circumstellar environment of the M-type AGB star R Dor. APEX spectral scan at $159.0-368.5$ GHz
• The abundance of C2H4 in the circumstellar envelope of IRC+10216
• The abundance of 28Si32S, 29Si32S, 28Si34S, and 30Si32S in the inner layers of the envelope of IRC+10216
• A Molecular Line Survey toward the Nearby Galaxies NGC 1068, NGC 253, and IC 342 at 3 mm with the Nobeyama 45-m Radio Telescope: Impact of an AGN on 1 kpc Scale Molecular Abundances
• 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
• Herschel/HIFI observations of IRC+10216: water vapor in the inner envelope of a carbon-rich AGB star
• Heteroatom-doped hydrogenated amorphous carbons, a-C:H:X 'Volatile' silicon, sulphur and nitrogen depletion, blue photoluminescence, diffuse interstellar bands and ferro-magnetic carbon grain connections (Research Note)
• A spectral line survey of IRC +10216 between 13.3 and 18.5 GHz
• A Molecular Line Survey of the Carbon-Rich Proto-Planetary Nebula AFGL 2688 in the 3mm and 1.3mm Windows
• Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes -- I. The case of hydrogen cyanide
• Developing a self-consistent AGB wind model: I. Chemical, thermal, and dynamical coupling
• Monitor variability of millimeter lines in IRC +10216
• Molecules in the carbon-rich protoplanetary nebula CRL 2688
• The chemistry of extragalactic carbon stars
• Reconciling spectroscopy with dynamics in global potential energy surfaces: the case of the astrophysically relevant SiC${}_2$
• A new off-point-less observing method for millimeter and submillimeter spectroscopy with a frequency-modulating local oscillator (FMLO)
• The Role of Ultraviolet Photons in Circumstellar Astrochemistry
• Charting Circumstellar Chemistry of Carbon-rich AGB Stars: I. ALMA 3 mm spectral surveys
• PACS and SPIRE range spectroscopy of cool, evolved stars
• Small carbon chains in circumstellar envelopes
• Detection of the linear SiC${}_3$ and SiC${}_5$ radicals in IRC\,+10216
• The spectra of evolved stars at 20--25\,GHz: tracing circumstellar chemistry during the asymptotic giant branch to planetary nebula transition
• Exploring circumstellar chemistry in X-ray emitting AGB stars
• APEX survey of interstellar HCl: ${}^{35}$Cl/${}^{37}$Cl isotopic ratios in dense cores and outflows
• IRC+10216 mass loss properties through the study of $\lambda$3mm emission: Large spatial scale distribution of SiO, SiS, and CS
• The Significant Role of Hydrogen in the Formation of Silicon Carbide in Evolved Stars
• New submillimetre HCN lasers in carbon-rich evolved stars