Volume 521, October 2010
Herschel/HIFI: first science highlights
|Number of page(s)||7|
|Published online||01 October 2010|
Letter to the Editor
A high-resolution line survey of IRC +10216 with Herschel/HIFI *,**
First results: Detection of warm silicon dicarbide (SiC)
Departamento de Astrofísica, Centro de Astrobiología, CSIC-INTA,
Ctra. de Torrejón a Ajalvir km 4, Torrejón de Ardoz, 28850 Madrid, Spain e-mail: email@example.com
2 Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park XH, Amsterdam, The Netherlands
3 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
4 LERMA and UMR 8112 du CNRS, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
5 Leiden observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
6 LUTH, Observatoire de Paris-Meudon, 5 place Jules Janssen, 92190 Meudon, France
7 I. Physikalisches Institut, University of Cologne, Germany
8 Dept of Physics & Astronomy, University College London, Gower St., London WC1E 6BT, UK
9 Institute of Astronomy, ETH Zurich, 8093 Zurich, Switzerland
10 INAF – Istituto di Fisica dello Spazio Interplanetario, Area di Ricerca di Tor Vergata, via Fosso del Cavaliere 100, 00133 Roma, Italy
11 Department of Physics and Astronomy, University of Waterloo, Waterloo, ON Canada N2L 3G1, Canada
12 Jet Propulsion Laboratory, 4800 Oak Grove Drive, MC 168-314, Pasadena, CA 91109, USA
13 European Space Astronomy Centre, ESA, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
14 Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
15 Department of Radio and Space Science, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
16 University of Massachusetts, Astronomy Dept., 710 N. Pleasant St., LGRT-619E, Amherst, MA 01003-9305, USA
17 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands
Accepted: 26 July 2010
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 1901 GHz. In this letter we focus on the band-1b spectrum, in a spectral range 554.5–636.5 GHz, 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 ~ 2 × 10-7 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 ~ 6.4 × 1015 cm-2. Furthermore, the high quality of the HIFI data set was used to improve the spectroscopic rotational constants of SiC2.
Key words: stars: individual: IRC+10216 / stars: carbon / stars: AGB and post-AGB / line: identification / astrochemistry
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Appendix (pages 6, 7) is only available in electronic form at http://www.aanda.org
© ESO, 2010
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