Volume 560, December 2013
|Number of page(s)||5|
|Published online||05 December 2013|
Detection of circumstellar nitric oxide
1 Centro de Astrobiología (CSIC-INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid, Spain
e-mail: email@example.com; firstname.lastname@example.org
2 Instituto de Radio Astronomía Milimétrica (IRAM), Avenida Divina Pastora, núcleo central, 18012 Granada, Spain
3 Univ. Bordeaux, LAB, UMR 5804, 33270 Floirac, France
4 CNRS, LAB, UMR 5804, 33270 Floirac, France
5 Observatorio Astronómico Nacional (IGN), Ap 112, 28803 Alcalá de Henares, Spain
6 Centro de Astrobiología (CSIC-INTA), ESAC Campus, 28691 Villanueva de la Cañada, Madrid, Spain
7 Institut de RadioAstronomie Millimétrique, 300 rue de la Piscine, 38406 Saint-Martin d’Hères, France
8 Observatorio Astronómico Nacional (IGN), Alfonso XII N3, 28014 Madrid, Spain
Received: 22 September 2013
Accepted: 29 October 2013
Aims. During a full line survey towards IRC +10420 in the 3 and 1 mm bands, we detected the emission of circumstellar nitric oxide for the first time. We aim to study the formation of NO and to confirm the enrichment of nitrogen expected for the most massive, evolved stars predicted by the hot bottom burning process.
Methods. We counted on a detailed model of the structure and kinematics of the molecular gas around IRC+˙10420. In addition, we used a chemical model to derive the NO abundance profile. We modified the initial nitrogen abundance in order to fit the observed NO profiles. These synthetic profiles were obtained using an LVG radiative transfer code.
Results. We have detected NO in a circumstellar envelope for the first time, along with a variety of N-rich molecules, which in turn shows that IRC +10420 presents a N-rich chemistry. Furthermore, we have found that to reproduce the observed NO line profiles, the initial abundance of nitrogen in the chemical model has to be increased by a factor 20 with respect to the values of the standard O-rich stars.
Key words: astrochemistry / line: identification / molecular processes / circumstellar matter / supergiants / stars: individual: IRC +10420
Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).
Figures 3 and 4 are available in electronic form at http://www.aanda.org
© ESO, 2013
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