EDP Sciences
Free access
Volume 384, Number 2, March III 2002
Page(s) 568 - 584
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20011814

A&A 384, 568-584 (2002)
DOI: 10.1051/0004-6361:20011814

Nanodiamonds around HD 97048 and Elias 1

C. Van Kerckhoven1, A. G. G. M Tielens2, 3 and C. Waelkens1

1  Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
2  Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
3  SRON, PO Box 800, 9700 AV Groningen, The Netherlands

(Received 5 June 2001 / Accepted 11 December 2001)

We present an analysis of ISO-SWS observations of the Herbig Ae/Be stars HD 97048 and Elias 1. Besides the well-known family of IR emission bands at 3.3, 6.2, "7.7", 8.6 and 11.2  $\mu$m these objects show strong, peculiar emission features at 3.43 and 3.53  $\mu$m. The latter two features show pronounced substructure which is very similar in the two sources. Comparison of the spectra of HD 97048 and Elias 1 with laboratory spectra of H-terminated diamond surfaces show excellent and very convincing agreement in peak position and spectral detail (Guillois et al. 1999). The position of the 3.53  $\mu$m band indicates a temperature of ~1000 K. An analysis of the radiative energy budget makes us conclude that the diamond carrier of the 3.53  $\mu$m feature has typical sizes of 1-10 nm for HD 97048. A fit of the 3.53  $\mu$m feature with a theoretical, calculated profile indicates that the emitting diamonds in HD 97048 see a FUV flux of 5.8 $\times$ 10 -3 [ W/cm 2] . The derived diamond mass, 1.5 $\times$ 10 -10  $M_{\odot}$, is only a tiny fraction of the total circumstellar dust mass and corresponds to only about 1 parts per billion relative to hydrogen. We discuss the origin of the diamond around these Herbig Ae/Be stars and conclude that most likely they are formed in situ. The implications for the nanodiamonds discovered in meteorites are also discussed.

Key words: circumstellar matter -- infrared: ISM: lines and bands -- ISM: general -- ISM: molecules, dust -- ISM: individual: HD 97048, Elias 1

Offprint request: C. Van Kerckhoven, caroline@ster.kuleuven.ac.be

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