Detection of anhydrous hydrochloric acid, HCl, in IRC +10216 with the <i>Herschel</i>SPIRE and PACS spectrometers

Cernicharo, J.; Decin, L.; Barlow, M. J.; Agúndez, M.; Royer, P.; Wesson, R.; Polehampton, E. T.; Beck, E. De; Blommaert, J. A. D. L.; Daniel, F.; Meester, W. De; Exter, Katrina; Feuchtgruber, H.; Gear, Walter Kieran; Goicoechea, J. R.; Gomez, Haley Louise; Groenewegen, M. A. T.; Hargrave, Peter Charles; Huygen, R.; Imhof, P.; Ivison, R. J.; Jean, C.; Kerschbaum, F.; Leeks, S. J.; Lim, T.; Matsuura, M.; Olofsson, G.; Posch, Th.; Regibo, S.; Savini, G.; Sibthorpe, B.; Swinyard, Bruce; Vandenbussche, B.; Waelkens, C.

doi:10.1051/0004-6361/201014553

Cited by 44 publications

(24 citation statements)

References 26 publications

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“…1), belonging to 10 different molecules and their isotopologues ( 12 CO, 13 CO, C 18 O, H 12 CN, H 13 CN, H 2 O, NH 3 , SiS, SiO, CS, C 34 S, 13 CS, C 3 , C 2 H, HCl, and H 37 Cl). The detection of this last molecule is discussed by Cernicharo et al (2010). In the ISO-LWS spectrum shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

Silicon in the dust formation zone of IRC +10216

Decin

Cernicharo

Barlow

et al. 2010

A&A

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The interstellar medium is enriched primarily by matter ejected from evolved low and intermediate mass stars. The outflows from these stars create a circumstellar envelope in which a rich gas-phase and dust-nucleation chemistry takes place. We observed the nearest carbon-rich evolved star, IRC +10216, using the PACS (55−210 μm) and SPIRE (194−672 μm) spectrometers on board Herschel. We find several tens of lines from SiS and SiO, including lines from the v = 1 vibrational level. For SiS these transitions range up to J = 124−123, corresponding to energies around 6700 K, while the highest detectable transition is J = 90−89 for SiO, which corresponds to an energy around 8400 K. Both species trace the dust formation zone of IRC +10216, and the broad energy ranges involved in their detected transitions permit us to derive the physical properties of the gas and the particular zone in which each species has been formed. This allows us to check the accuracy of chemical thermodynamical equilibrium models and the suggested depletion of SiS and SiO due to accretion onto dust grains.

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Section: Resultsmentioning

confidence: 97%

Silicon in the dust formation zone of IRC +10216

Decin

Cernicharo

Barlow

et al. 2010

A&A

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“…The quality of the acquired data permits the detection of lines as weak as 1−2 Jy. For the technical background and a description of the data-reduction process we refer to the discussions by Cernicharo et al (2010a) and Decin et al (2010b). These authors report uncertainties on the SPIRE FTS absolute fluxes of the order of 15−20% for SSW data, 20−30% for SLW data below 500 μm, and up to 50% for SLW data beyond 500 μm.…”

Section: Herschel/spirementioning

confidence: 99%

On the physical structure of IRC +10216

Beck

Lombaert

Agúndez

et al. 2012

A&A

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106

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Context. The carbon-rich asymptotic giant branch star IRC +10 216 undergoes strong mass loss, and quasi-periodic enhancements of the density of the circumstellar matter have previously been reported. The star's circumstellar environment is a well-studied and complex astrochemical laboratory, in which many molecular species have been proved to be present. CO is ubiquitous in the circumstellar envelope, while emission from the ethynyl (C 2 H) radical is detected in a spatially confined shell around IRC +10 216. We recently detected unexpectedly strong emission from the N = 4−3, 6−5, 7−6, 8−7, and 9−8 transitions of C 2 H with the IRAM 30 m telescope and with Herschel/HIFI, which challenges the available chemical and physical models. Aims. We aim to constrain the physical properties of the circumstellar envelope of IRC +10 216, including the effect of episodic mass loss on the observed emission lines. In particular, we aim to determine the excitation region and conditions of C 2 H to explain the recent detections and to reconcile them with interferometric maps of the N = 1−0 transition of C 2 H. Methods. Using radiative-transfer modelling, we provide a physical description of the circumstellar envelope of IRC +10 216, constrained by the spectral-energy distribution and a sample of 20 high-resolution and 29 low-resolution CO lines -to date, the largest modelled range of CO lines towards an evolved star. We furthermore present the most detailed radiative-transfer analysis of C 2 H that has been done so far. Results. Assuming a distance of 150 pc to IRC +10 216, the spectral-energy distribution was modelled with a stellar luminosity of 11300 L and a dust-mass-loss rate of 4.0 × 10 −8 M yr −1 . Based on the analysis of the 20 high-frequency-resolution CO observations, an average gas-mass-loss rate for the last 1000 years of 1.5 × 10 −5 M yr −1 was derived. This results in a gas-to-dust-mass ratio of 375, typical for this type of star. The kinetic temperature throughout the circumstellar envelope is characterised by three power laws: T kin (r) ∝ r −0.58 for radii r ≤ 9 stellar radii, T kin (r) ∝ r −0.40 for radii 9 ≤ r ≤ 65 stellar radii, and T kin (r) ∝ r −1.20 for radii r ≥ 65 stellar radii. This model successfully describes all 49 observed CO lines. We also show the effect of density enhancements in the wind of IRC +10 216 on the C 2 H-abundance profile, and the close agreement we find of the model predictions with interferometric maps of the C 2 H N = 1−0 transition and with the rotational lines observed with the IRAM 30 m telescope and Herschel/HIFI. We report on the importance of radiative pumping to the vibrationally excited levels of C 2 H and the significant effect this pumping mechanism has on the excitation of all levels of the C 2 H-molecule.

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“…The chemistry of other diatomic hydrides with heavier (e.g., X=Fe) and/or less abundant elements (e.g., X=F) is not discussed here, as their chemistry is poorly known and their use as tracers is currently limited. However, with the ongoing search for new diatomic hydrides using the new Herschel Space Observatory (e.g., Cernicharo et al 2010), this situation may change. For example, Neufeld et al (2010) report the detection of HF using the HIFI instrument on board Herschel.…”

Section: Introductionmentioning

confidence: 99%

Multidimensional Chemical Modeling of Young Stellar Objects. Iii. The Influence of Geometry on the Abundance and Excitation of Diatomic Hydrides

Bruderer

Benz

Stäuber

et al. 2010

ApJ

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The Herschel Space Observatory enables observations in the far-infrared at high spectral and spatial resolution. A particular class of molecules will be directly observable: light diatomic hydrides and their ions (CH, OH, SH, NH, CH + , OH + , SH + , NH + ). These simple constituents are important both for the chemical evolution of the region and as tracers of high-energy radiation. If outflows of a forming star erode cavities in the envelope, protostellar far-UV (FUV; 6 < E γ < 13.6 eV) radiation may escape through such low-density regions. Depending on the shape of the cavity, the FUV radiation then irradiates the quiescent envelope in the walls along the outflow. The chemical composition in these outflow walls is altered by photoreactions and heating via FUV photons in a manner similar to photo-dominated regions. In this work, we study the effect of cavity shapes, outflow density, and of a disk with the two-dimensional chemical model of a high-mass young stellar object introduced in the second paper in this series. The model has been extended with a self-consistent calculation of the dust temperature and a multi-zone escape probability method for the calculation of the molecular excitation and the prediction of line fluxes. We find that the shape of the cavity is particularly important in the innermost part of the envelope, where the dust temperatures are high enough ( 100 K) for water ice to evaporate. If the cavity shape allows FUV radiation to penetrate this hot-core region, the abundance of FUV-destroyed species (e.g., water) is decreased. On larger scales, the shape of the cavity is less important for the chemistry in the outflow wall. In particular, diatomic hydrides and their ions CH + , OH + , and NH + are enhanced by many orders of magnitude in the outflow walls due to the combination of high gas temperatures and rapid photodissociation of more saturated species. The enhancement of these diatomic hydrides is sufficient for a detection using the HIFI and PACS instruments on board Herschel. The effect of X-ray ionization on the chemistry is found to be small, due to the much larger luminosity in FUV bands compared to X-rays.

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Detection of anhydrous hydrochloric acid, HCl, in IRC +10216 with the HerschelSPIRE and PACS spectrometers

Cited by 44 publications

References 26 publications

Silicon in the dust formation zone of IRC +10216

Silicon in the dust formation zone of IRC +10216

On the physical structure of IRC +10216

Multidimensional Chemical Modeling of Young Stellar Objects. Iii. The Influence of Geometry on the Abundance and Excitation of Diatomic Hydrides

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